Chemical formula of ice. What is ice, properties of ice

Previously, it was quite logical that when you bought a compact camera, you received a small matrix, and if you chose a large-sized DSLR with interchangeable lenses, the matrix on it was much larger. This affected the quality of the photographs, since the larger the matrix, the more detailed the images were.

Now this, in principle, is also relevant to some extent, the matrix is the most expensive part of the camera in terms of production, and the larger the matrix, the more expensive the camera is, accordingly. That’s why expensive cameras usually don’t have 1/2.3-inch matrices installed, and cheap ones, accordingly, can’t find a full-frame one.

But it must be said that now many manufacturers have begun to offer compact cameras with relatively large matrices, just like cameras for interchangeable lenses with smaller matrices. So it has perhaps become more difficult to understand the situation. Small matrices can work well in different conditions, and even have some advantages over larger ones.

Behind last years and the technology for creating matrices has advanced significantly, so today a large number of The options offered can confuse even an experienced user, let alone those who are purchasing their first camera. But the size of the matrix also affects the focal length, so you really need to take a lot into account when choosing a camera.

So, we decided to understand the different types of matrices to put everything in its place. But first you need to clarify exactly how the size of the matrix affects the effective focal length.

Focal length

So, we have already found out that the size of the matrix is related to the focal length, that is, to which lens is suitable for your camera. If you purchase a compact device with a non-removable lens, the problem disappears by itself, that is, from the buyer’s position it is much simpler. But it’s not for nothing that professionals choose those cameras where lenses can be changed. Any lens must have an image field (circle) or diameter of light that exists in the lens and that covers the size of the sensor. There is one exception, which we will return to later.

So, built-in or not, lenses are always labeled with the actual focal length, not the effective focal length you will get when used on a particular camera. But the problem is that different lenses with different markings may end up providing the same focal length to work with. Why? Because they are designed for different matrices. That is why, in addition to markings, manufacturers indicate the equivalent, where the main distance is considered to be 35mm or a full-frame matrix.

Here is one example: a camera with a sensor smaller than a full frame can be used with an 18-55mm lens, but in reality the focal length you will get will be closer to 27-82mm. This all happens because the sensor is not large enough to use the lens in the same way as a full frame could. Because the peripheral space inside the lens is not taken into account, the effect is the same as using a lens with a longer focal length.

Compact cameras may have a 19mm lens, but due to the sensor size being smaller than a full frame, you will end up with a longer focal length, around 28mm. The exact length is determined by the crop factor, that is, the number by which you need to increase the focal length given for a full frame in order to find out what distance you will get on a particular camera.

Matrix sizes

1/2.3 inch

The size of such a matrix is approximately 6.3 x 4.7 mm. This is the smallest matrix that can be found in modern cameras, and most often in budget compact models. The resolution of such a matrix is, as a rule, 16-20 megapixels.

At least this arrangement was the most popular some time ago. Today, many manufacturers have begun to place more emphasis on amateur cameras with large matrices, so this size is not as common as before.

However, the advantage is that this size allows you to get a compact camera and use it with long lenses, such as compact superzooms. And a larger matrix means that you will need a larger lens.

In good lighting, such cameras can provide good results, but for more picky photographers they are definitely not suitable, since they will produce grain in low light.

1/1.7 inches

The size of these matrices is 7.6 x 5.7mm. With such a matrix it is much easier to isolate the subject from the background, and accordingly, performance in terms of details both in the shadows and in the light. So they can be used in more diverse conditions. Previously, such cameras were the most common among amateurs, but now their place is rapidly being taken by inch matrices, which will be discussed further.

But 1/1.7 inch matrices are used in some relatively outdated Pentax Q-series cameras.

Inch matrices

Inch matrix size 13.2mm x 8.8mm. Today, such matrices are very popular on various types of cameras; their size allows them to remain light and compact. It is logical that the most popular use for an inch matrix is in pocket amateur cameras, on which the lens will be limited to 24-70mm or 24-100mm (if we take the 35mm equivalent). However, it is also used on some superzoom cameras, examples are the Sony RX10 III and Panasonic FZ2000.

We are much more familiar with the inch matrix from Nikon series 1 cameras, for example Nikon 1 J5 - an excellent and lightweight camera that can do great photo and shoot 4K video. Such a matrix can be found even among smartphones - Panasonic CM1.

Cameras with an inch matrix are able to show results that are significantly different from previous options. Their quality will be high, and even compact cameras usually have a wide maximum aperture, so that enough light reaches the sensor, so the photos come out clear and sharp.

In part, this is a result of technology, not just sensor size. Modernly manufactured matrices can capture light more efficiently.

Micro 4/3

The micro 4/3 matrix has a physical size of 17.3 x 13mm. This format is used in compact DSLRs and mirrorless cameras from Olympus and Panasonic. They are not much larger in size than inch matrices, but smaller than APS-C, which will be discussed below.

In fact, micro 4/3 is a quarter of the size of a full-frame sensor, so calculating the active focal length for it is extremely simple: just multiply the focal length by 2.

In other words, a 17mm lens on a camera with a micro 4/3 sensor will provide the same focal length as a 34mm lens on a full frame sensor. By analogy, 12-35mm will give 24-70mm and so on.

The Lumix DMC-LX100 camera uses a micro 4/3 matrix with a resolution of 12.8 megapixels. This is one of the compact digital cameras that comes with a lot of features in a small size. The camera is equipped with a Leica lens with a focal length of 24-75mm.

APS-C

The average physical size of such a matrix is 23.5 x 15.6 mm. This matrix is used on SLR cameras for beginners and amateur cameras, and now on many mirrorless cameras. The APS-C sensor provides an excellent balance between image quality, size and flexibility in terms of compatibility with different lenses.

Not all APS-C matrices are the same in size, because it also depends on the manufacturer. For example, APS-C matrices on Canon cameras are physically slightly smaller than those installed on Nikon and Sony, so its crop factor is 1.6x rather than 1.5x. In any case, APS-C is always a great option and professional photographers often prefer it for shooting nature and sports events, because thanks to the crop factor it is possible to “get closer” to the subject with the existing lens.

APS-C is available on some compact cameras, such as the Fujifilm X100F, and provides high-quality photography on portable cameras, especially when paired with prime lenses. The 23mm lens on the Fujifilm X100F has a wide maximum aperture, so you can easily achieve a narrow depth of field with this camera.

APS-H

The size of APS-H matrices is usually 26.6 x 17.9 mm. Today this format is practically not found, and is associated only with outdated Canon EOS-1D models (EOS-1D Mark III and Mark IV). Now, however, this series uses full frames.

Since APS-H is larger than APS-C, but smaller than a full-frame sensor, the crop factor is correspondingly equal to 1.3x, so a 24mm lens will provide a focal length of approximately 31mm on such a camera.

One of the last cameras where you can find such a matrix is the Sigma sd Quattro H. However, Canon decided not to abandon APS-H completely, and preferred to use this matrix for surveillance cameras rather than for SLR cameras.

Fullframe

36 x 24mm is also a full frame, it is also a full frame matrix and it is approximately the same size as a film photograph negative. Full-frame matrices are used in amateur and professional cameras ah and are considered the most convenient option for filming. The size of such a matrix allows it to absorb more light, as a result of which the photos are of higher quality than with smaller matrices. Accordingly, when it comes to the number of pixels, there is more choice. And the resolution of full-frame matrices varies from 12 to 50 megapixels.

The crop factor, of course, does not matter in the case of a full-frame matrix, since the lens markings will correspond to the active focal length. However, some lenses created for APS-C matrices can still be used with full frames, but the resolution will be limited (the camera will crop the corners to avoid vignetting). But, of course, you always need to check compatibility, otherwise there is a risk of damaging the mirror.

Average (medium) matrix

44mm x 33mm is the size of such a matrix. This is obviously more than a full frame and since their appearance such matrices have aroused intense interest and discussion. They are used in the Fujifilm GFX 50S, Hasselblad X1D and Pentax 645Z cameras, the latter being slightly older than the others. They are mainly used exclusively professional photographers due to the price of such cameras and their specifics.

It’s not a fact that the development of matrices as such will stop here, but for now these are all types of matrices available on the market, and it’s up to you to decide which one is suitable for your photo interests.

This chapter is devoted to the question: how does the sensor size of a digital camera affect Various types photos? The choice of sensor size is similar to the choice between 35mm, medium and large format film cameras - with some significant differences inherent in digital technology. This topic generates a lot of confusion because sensor sizes vary widely and there are many options to choose from, including depth of field, visual noise, diffraction, cost, and size/weight.

I wrote this article after doing my own research to see if the Canon EOS 5D was actually a step up from the 20D for my purposes. The basic concepts discussed in this article can be found in the chapter on digital camera sensors.

Overview of sensor sizes

There are many sensors of different sizes, depending on their use, price range and required portability. The relative sizes for many of them are shown below:

Canon 1Ds/1DsMkII/5D and Kodak DCS 14n are the most common full-frame sensors. Canon cameras like 300D/350D/10D/20D all use 1.6 crop factor while Nikon cameras like D70(s)/D100 use 1.5 crop factor. The chart lacks the 1.3 crop factor used in Canon's 1D camera series.

Phone cameras and other compact cameras use sensors ranging from ~1/4" to 2/3". Olympus, Fuji and Kodak teamed up to create the 4/3 standard, which has a crop factor of 2 relative to 35mm film. There are medium format and even larger sensors, but they are much less common and currently impossibly expensive, so we are not covering them here, although the same principles apply.

Crop factor and focal length multiplier

The crop factor is the ratio of the diagonal of the full frame (35 mm) to the diagonal of the sensor. It is called this because when using a 35mm lens, the sensor essentially cuts off the edges of the image (due to its reduced size).

At first glance, you might think that losing image information would never be appropriate, but in reality it has its benefits. Almost all lenses are sharpest in the central part, and as you approach the edge, quality degradation increases. It means that a downsized sensor essentially loses parts of the image of poorer quality, which can be very useful when using low quality lenses (since they tend to have the worst edge quality).

On the other hand, this means that a much larger lens is used than is actually necessary - which becomes especially noticeable if the camera has to be worn for a long time (see below). Ideally, you would use virtually the entire image produced by the lens, and the lens should be of high enough quality that the changes in sharpness from the center to the edges are negligible.

In addition, the optical quality of wide-angle lenses is rarely as good as that of lenses with longer focal lengths. Since a cropped sensor is forced to use wider-angle lenses to achieve the viewing angles possible with a larger sensor, this degrades quality. Additionally, smaller sensors make greater use of the lens's central field of view, so the limits of its resolution will become more noticeable with lower quality lenses.

Likewise, the focal length multiplier relates the focal length of a lens used with a smaller format sensor to the focal length of a lens with the same angle of view at 35mm, and is equal to the crop factor. This means that a 50mm lens used with a sensor whose crop factor is 1.6 will provide the same angle of view as a 1.6 x 50 = 80mm lens on a full frame 35mm sensor.

Please note that each of these terms can be somewhat misleading. The focal length of a lens doesn't really change when used with a different size sensor - only the angle of view changes. A 50mm lens will always be a 50mm lens, regardless of the sensor type. However, “crop factor” may not be an appropriate term to describe small sensors, since image cropping does not always occur (if lenses designed for that sensor are used).

Lens size and weight

Smaller sensors require lighter lenses(for equivalent angle of view, zoom range, build quality and aperture range). This difference can be critical for filming wildlife, hiking and travel, as they often require the use of heavier lenses or carrying equipment for long periods of time. The following graph illustrates this trend using a selection of typical Canon telephoto lenses for sports and wildlife photography:

This means that if you want to achieve the same zoom on a 35mm camera as a 200mm f/2.8 lens on a camera with a crop factor of 1.5 (i.e. using a 300mm f/2.8 lens), you will have to carry 3.5 times the weight! This is without taking into account the difference in size between them, which can be important if you don’t want to attract public attention. Additionally, heavier lenses tend to cost significantly more.

In DSLR cameras, increasing the sensor size also means increasing the size and transparency of the image in the viewfinder, which can be especially useful when manually focusing. However, this design will also be heavier and cost more because it requires a larger pentaprism (or pentamirror) to transfer light from the lens to the viewfinder and on to the retina of your eye.

Depth of field requirements

As the sensor size increases, the depth of field at a given aperture will decrease (for a subject of the same size and at the same distance). This happens because a larger sensor will require you to either move closer to your subject or use a longer focal length to fill the frame. Reducing the focusing distance means reducing the depth of field, to compensate for which you will need to increase the aperture number (close it further). The following calculator determines the required aperture and focal length to maintain depth of field (with the same perspective).

As an example calculation, if you wanted to reproduce the same perspective and depth of field on a full frame sensor that was achieved with a 10mm lens at f/11 on a camera with a 1.6 crop factor, you would need to use a 16mm lens and an aperture of about f/ 18. Otherwise, if you use a 50mm f/1.4 lens on a full-frame sensor, the resulting depth of field would be so shallow that on a camera with a 1.6 crop factor it would require an aperture of 0.9 - unattainable for consumer lenses!

A shallow depth of field may be desirable for portraits because it improves background blur, while a deep depth of field is desirable for landscape photography. This is why compact cameras struggle to get good background blur in portraits, while large format cameras struggle to get the required depth of field in landscapes.

Please note that the above calculator assumes that you have a lens for the second sensor that can replicate the angle of view of the first. If you use the same lens, the aperture requirements will remain the same, but you will need to get closer to (or further away from) the subject. However, this will also change the perspective.

Effect of diffraction

Larger sensors can use smaller apertures before the circle of confusion becomes larger than the circle of confusion (determined by the print size and sharpness criteria). This happens primarily because large sensors do not require such a large increase in the image captured by them to obtain a similar printed size. For example, using a (theoretically) 20x25cm digital sensor, 8x10cm prints would not require enlargement at all, whereas a print from a 35mm sensor would require significant enlargement.

The following calculator can be used to estimate the diffraction limit of sharpness. Please note that his results are only valid for visual inspection of the screen image at 100% scale - that is, the discernibility of diffraction in the print will also depend on viewing distance and print size. To obtain a calculation for these parameters, use the calculator provided in the chapter on the diffraction limit in photography.

Remember that the effect of diffraction increases gradually, so apertures slightly smaller or larger than the obtained diffraction limit value will not suddenly look better or worse, respectively. Using the Canon 20D, for example, you can often go to f/11 without noticeable changes in focal plane sharpness, but stop down further and diffraction becomes noticeable. Further, the above figure is just a theoretical limit, in reality the value will also depend on the characteristics of the lens. The following chart shows the size of the Airy disk (theoretical maximum resolution) for two apertures in a pixel size matrix:

An important consequence of these phenomena is that diffraction limit of pixel size increases for larger sensors(if the required depth of field remains unchanged). It is pixel size that determines the point at which the size of the circle of dispersion becomes the limiting factor of overall resolution - not pixel density. Further, the diffraction limit of the depth of field is constant for all sensor sizes. This factor can be critical when choosing a new camera for the intended use, since more pixels will not necessarily provide an increase in resolution (for certain depth of field requirements). In fact, increasing the number of pixels can even harm image quality by increasing noise and reducing dynamic range (in the next section).

Pixel Size: Noise Level and Dynamic Range

Larger sensors usually have larger pixels (though this is not always the case), which potentially means less visual noise and greater dynamic range. Dynamic range describes the range of chromaticities that the sensor is able to record before the pixel is completely white, but not below the level at which the texture becomes indistinguishable from background noise (close to black). Because larger pixels occupy more volume - and therefore have greater photonic capacity - their dynamic range also tends to be greater.

Note: containers shown without color filters

Further, larger pixels receive more photons during a given exposure (at the same aperture), so their light signal is much stronger. For a similar amount of background noise, a higher signal-to-noise ratio is achieved - and as a result, a smoother photo.

However, this is not always the case, since the level of background noise also depends on the manufacturing technology of the sensor and how efficiently the camera extracts tonal information from each pixel (without introducing additional noise). Otherwise, the above trend is correct. Another aspect to consider is that even if two sensors have the same visible noise when viewed at 100%, the sensor with more pixels will produce a cleaner final print. This will happen because on a sensor with a higher number of pixels the noise will be less magnified (for a given print size), therefore it will be higher frequency noise with a finer grain.

Cost of producing a digital sensor

The cost of a digital sensor increases dramatically as its area increases. This means that a sensor with twice the area will cost much more than twice as much, so you are actually paying more per unit of sensor area as it gets larger.

You can understand this by looking at the production process of digital sensors. Each sensor is cut from a large sheet of silicon, called a substrate, which can contain thousands of individual chips. Each sheet is incredibly expensive (thousands of dollars), and as a result, the fewer chips that can be obtained from a sheet, the more expensive each one will be. Further, the degree of rejection (too many burnt pixels or something else) increases as the size of the sensor increases, that is, the percentage of usable sensors (yield from the sheet) decreases. Considering these factors (the number of chips per sheet and income) to be the most important, we consider the cost to increase in proportion to the square of the sensor area (a double-size sensor will cost four times more). In reality, the relationship between size and cost is more complex, but a quadratic calculation can help you estimate how quickly costs are rising.

This doesn't mean that sensors of a certain size will always be prohibitively expensive; their cost may one day fall, but the relative cost of a large sensor will always be much greater (per unit area) compared to some smaller size.

Other Considerations

Some lenses are only available for certain sensor sizes(they may not work otherwise), which may also be a consideration if you need them for your photography style. One notable type of lens is the tilt/shift lens, which can be used to increase (or decrease) the apparent depth of field by rotating or to control perspective using shift to reduce (or eliminate) vertical roll caused by camera deviation from the horizon line (useful when photographing architecture).

Results: overall image detail and mutually exclusive factors

The depth of field for large format sensors is much shallower, but they also allow the aperture to be closed much further before the diffraction limit is reached (for the selected print size and sharpness criteria). So which option has the potential to capture the most detail? Larger sensors (and correspondingly larger pixel counts) no doubt produce more detailed images if you can afford to sacrifice depth of field. On the other hand, if you want to maintain a certain depth of field, larger sensor sizes do not necessarily have a resolution advantage. Further, diffraction limit of depth of field is the same for all sensor sizes. In other words, if you want to use a very small aperture before diffraction occurs, all sensor sizes will produce the same depth of field - even though the diffraction limit of the aperture number will be different.

Technical Note: This assumes that the pixel size is comparable to the size of the diffraction circle (Airy disk) for each sensor and that lenses of comparable quality are used. Moreover, rotating lenses are much more common for large format cameras - allowing you to change the angle of the focal plane and, as a result, increase visible depth of field.

Another important consequence is that if depth of field is a critical parameter, the required exposure time increases with sensor size for the same ISO sensitivity. This factor has perhaps the greatest impact on macro photography and night photography, as each may require a large depth of field and reasonable exposure times. Note that while a photo can be taken handheld on a smaller format, it may not necessarily be possible to shoot handheld on a larger format.

On the other hand, shutter durations won't necessarily increase as much as they might seem at first glance, since larger sensors tend to be less noisy (and therefore can allow higher ISO sensitivities to be used while maintaining similar levels of visual noise).

Ideally, visual noise levels (at a given print size) generally fall as the digital camera sensor size increases (regardless of pixel size).

Regardless of pixel size, larger sensors inevitably have a larger light collection area. Theoretically the sensor big size with small pixels will still show less visual noise (for the selected print size) than a smaller sensor with larger pixels (and significantly fewer pixels as a consequence), since high-resolution camera noise is subject to less magnification, even when viewed At 100% scale, the image looks noisier on a computer screen. Otherwise, it is possible to average adjacent pixels from a sensor with a larger number of pixels (thereby reducing random noise), while achieving the resolution of a sensor with a smaller number of pixels. This is why images reduced for publishing on websites and small-size prints look so silent.

Technical Notes: All of these statements assume that the differences in microlens efficiency and interpixel spacing for different sensor sizes are negligible. If the inter-pixel distance remains unchanged (due to the presence of readout circuits and other circuitry on the chip), a higher pixel density means a reduction in the light collector area if the microlenses cannot compensate for these losses. In addition, it ignores the influence of structure and line noise, which can vary significantly between camera models and sensor readout circuitry.

In general: Larger sensors typically provide more control and artistic flexibility, but at the cost of increased lens size, weight, and overall cost. This flexibility allows you to use a shallower depth of field than is possible with a smaller sensor (if required), while still achieving comparable depth of field using a smaller aperture and higher ISO sensitivity (or a tripod).

Vendors now offer a huge selection of video surveillance cameras. Models differ not only in parameters common to all cameras - focal length, viewing angle, light sensitivity, etc. - but also in various proprietary features that each manufacturer strives to equip their devices with.

Therefore, often short description characteristics of a video surveillance camera is a frightening list of incomprehensible terms, for example: 1/2.8" 2.4MP CMOS, 25/30fps, OSD Menu, DWDR, ICR, AWB, AGC, BLC, 3DNR, Smart IR, IP67, 0.05 Lux and that's not all.

In the previous article, we focused on video standards and the classification of cameras depending on them. Today we will look at the main characteristics of video surveillance cameras and deciphering the symbols of special technologies used to improve the quality of the video signal:

Focal length and viewing angle
Aperture (F number) or lens aperture
Adjusting the iris (auto iris)
Electronic shutter (AES, shutter speed, shutter speed)
Sensitivity (light sensitivity, minimum illumination)
Protection classes IK (Vandal-proof, anti-vandal) and IP (from moisture and dust)

Matrix type (CCD CCD, CMOS CMOS)

There are 2 types of CCTV camera matrices: CCD (in Russian - CCD) and CMOS (in Russian - CMOS). They differ in both structure and principle of operation.

CCD	CMOS
Sequential reading from all matrix cells	Random reading from matrix cells, which reduces the risk of smearing - the appearance of vertical smearing of point light sources (lamps, lanterns)
Low noise level	High noise level due to so-called tempo currents
High dynamic sensitivity (more suitable for shooting moving objects)	“Rolling shutter” effect - when shooting fast moving objects, horizontal stripes and image distortion may occur
The crystal is used only to accommodate photosensitive elements; the remaining microcircuits must be placed separately, which increases the size and cost of the camera	All chips can be placed on a single chip, making production of CMOS cameras simple and inexpensive
By using the matrix area only for photosensitive elements, the efficiency of its use increases - it approaches 100%	Low power consumption (almost 100 times less than CCD matrices)
Expensive and complex production	Performance

For a long time it was believed that the CCD matrix produces much higher quality images than CMOS. However, modern CMOS matrices are often practically in no way inferior to CCDs, especially if the requirements for the video surveillance system are not too high.

Matrix size

Indicates the diagonal size of the matrix in inches and is written as a fraction: 1/3", 1/2", 1/4", etc.

It is generally believed that the larger the matrix size, the better: less noise, clearer picture, larger viewing angle. However, in fact, the best image quality is provided not by the size of the matrix, but by the size of its individual cell or pixel - the larger it is, the better. Therefore, when choosing a video surveillance camera, you need to consider the matrix size along with the number of pixels.

If matrices with sizes 1/3" and 1/4" have the same number of pixels, then in this case a 1/3" matrix will naturally give a better image. But if it has more pixels, then you need to pick up a calculator and calculate the approximate pixel size.

For example, from the matrix cell size calculations below, you can see that in many cases the pixel size on a 1/4" matrix turns out to be larger than on a 1/3" matrix, which means a video image with 1/4", although it is smaller in size, it will be better.

Matrix size	Number of pixels (millions)	Cell size (µm)
1/6	0.8	2,30
1/3	3,1	2,35
1/3,4	2,2	2,30
1/3,6	2,1	2,40
1/3,4	2,23	2,45
1/4	1,55	2,50
1 / 4,7	1,07	2,50
1/4	1,33	2,70
1/4	1,2	2,80
1/6	0,54	2,84
1 / 3,6	1,33	3,00
1/3,8	1,02	3,30
1/4	0,8	3,50
1/4	0,45	4,60

Focal length and viewing angle

These options have great importance when choosing a CCTV camera, and they are closely related. In fact, the focal length of a lens (often denoted f) is the distance between the lens and the sensor.

In practice, the focal length determines the camera's viewing angle and range:

the shorter the focal length, the wider the viewing angle and the less detail can be seen on objects located in the distance;
The longer the focal length, the narrower the viewing angle of the video camera and the more detailed the image of distant objects.

If you need general review of some area, and you want to use as few cameras as possible for this - buy a camera with a short focal length and, accordingly, a wide viewing angle.

But in those areas where detailed observation of a relatively small area is required, it is better to install a camera with an increased focal length, pointing it at the object of observation. This is often used at the checkout counters of supermarkets and banks, where you need to see the denomination of banknotes and other payment details, as well as at the entrance to parking lots and other areas where it is necessary to distinguish a license plate number over a long distance.

The most common focal length is 3.6 mm. It roughly corresponds to the viewing angle of the human eye. Cameras with this focal length are used for video surveillance in small spaces.

The table below contains information and relationships between focal length, viewing angle, recognition distance, etc. for the most common focuses. The numbers are approximate, as they depend not only on the focal length, but also on other parameters of the camera optics.

Depending on the width of the viewing angle, video surveillance cameras are usually divided into:

conventional (viewing angle 30°-70°);
wide-angle (viewing angle from approximately 70°);
long-focus (viewing angle less than 30°).

The letter F, only usually capitalized, also denotes the lens aperture - therefore, when reading the characteristics, pay attention to the context in which the parameter is used.

Lens type

Fixed (monofocal) lens- the simplest and most inexpensive. The focal length is fixed and cannot be changed.

IN varifocal (variofocal) lenses you can change the focal length. Its setting is done manually, usually once when the camera is installed at the shooting location, and then as needed.

Transfactor or zoom lenses They also provide the ability to change the focal length, but remotely, at any time. The focal length is changed using an electric drive, which is why they are also called motorized lenses.

"Fisheye" (fisheye, fisheye) or panoramic lens allows you to install just one camera and achieve a 360° view.

Of course, the resulting image has a “bubble” effect - straight lines are curved, but in most cases, cameras with such lenses allow you to divide one general panoramic image into several separate ones, with adjustments for the perception familiar to the human eye.

Pinhole lenses allow for covert video surveillance due to its miniature size. In fact, a pinhole camera does not have a lens, but only a miniature hole instead. In Ukraine, the use of covert video surveillance is seriously limited, as is the sale of devices for it.

These are the most common lens types. But if we go deeper, lenses are also divided according to other parameters:

Aperture (F number) or lens aperture

Determines the camera's ability to capture high-quality images in low-light conditions. How larger number F, the smaller the aperture is and the more light the camera needs. The smaller the aperture, the wider the aperture is, and the camcorder can produce clear images even in low light.

The letter f (usually lowercase) also denotes the focal length, so when reading the characteristics, pay attention to the context in which the parameter is used. For example, in the picture above, the aperture is indicated by a small f.

Lens mount

There are 3 types of mounts for attaching a lens to a video camera: C, CS, M12.

The C mount is rarely used anymore. C lenses can be mounted on a CS mount camera using a special ring.
The CS mount is the most common type. CS lenses are not compatible with C cameras.
The M12 mount is used for small lenses.

Iris adjustment (auto iris), ARD, ARD

The diaphragm is responsible for the flow of light onto the matrix: with an increased flow of light, it narrows, thus preventing the image from being overexposed, and in low light, on the contrary, it opens so that more light falls on the matrix.

There are two large groups cameras: fixed aperture(this also includes cameras without it at all) and with adjustable.

The aperture can be adjusted in various models of video surveillance cameras:

Manually.
Automatically video camera using direct current, based on the amount of light hitting the sensor. This automatic iris adjustment (ADA) is referred to as DD (Direct Drive) or DD/DC.
Automatically a special module built into the lens and tracking the light flux passing through the relative aperture. This method of ARD in the specifications of video cameras is designated as VD (Video Drive). It is effective even when hitting the lens directly sun rays, but surveillance cameras with it are more expensive.

Electronic shutter (AES, shutter speed, shutter speed, shutter)

Different manufacturers may refer to this parameter as an automatic electronic shutter, shutter speed or shutter speed, but essentially it means the same thing - the time during which light is exposed to the matrix. It is usually expressed as 1/50-1/100000s.

The action of the electronic shutter is somewhat similar to automatic iris adjustment - it adjusts the light sensitivity of the matrix to adjust it to the light level of the room. In the figure below you can see the image quality in low light conditions with different speeds shutter (the picture shows manual adjustment, while AES does it automatically).

Unlike ARD, adjustment occurs not by adjusting the light flux entering the matrix, but by adjusting the shutter speed, the duration of the accumulation of electrical charge on the matrix.

However the capabilities of the electronic shutter are much weaker than automatic iris adjustment, therefore on open spaces, where the level of illumination varies from twilight to bright sunlight, it is better to use cameras with ARD. Video cameras with an electronic shutter are optimal for rooms where the light level changes little over time.

The characteristics of the electronic shutter differ little between different models. A useful feature is the ability to manually adjust the shutter speed (shutter speed), since in low light conditions low values are automatically set, and this leads to blurred images of moving objects.

Sens-UP (or DSS)

This is a function of accumulating the charge of the matrix depending on the level of illumination, i.e. increasing its sensitivity at the expense of speed. Necessary for shooting high-quality picture in poor lighting conditions, when tracking high-speed events is not critical (there are no fast moving objects at the observation object).

It is closely related to the shutter speed (shutter speed) described above. But if the shutter speed is expressed in time units, then Sens-UP is expressed in the shutter speed increase factor (xN): the charge accumulation time (shutter speed) increases by N times.

Permission

We touched on the topic of CCTV camera resolutions a little in the last article. Camera resolution is, in fact, the size of the resulting image. It is measured either in TVL (television lines) or in pixels. The higher the resolution, the more detail you will be able to see in the video.

Video camera resolution in TVL- this is the number of vertical lines (brightness transitions) placed horizontally in the picture. It is considered more accurate because it gives an idea of the size of the output image. While the resolution in megapixels indicated in the manufacturer's documentation can mislead the buyer - it often refers not to the size of the final image, but to the number of pixels on the matrix. In this case, you need to pay attention to such a parameter as “Effective number of pixels”

Resolution in pixels- this is the horizontal and vertical size of the picture (if it is specified as 1280x960) or the total number of pixels in the picture (if it is specified as 1 MP (megapixel), 2 MP, etc.). Actually, the resolution in megapixels is very simple to obtain: you need to multiply the number of horizontal pixels (1280) by the number of vertical pixels (960) and divide by 1,000,000. Total 1280×960 = 1.23 MP.

How to convert TVL to pixels and vice versa? There is no exact conversion formula. To determine the video resolution in TVL, you need to use special test tables for video cameras. For an approximate representation of the ratio, you can use the table:

Effective pixels

As we said above, often the size in megapixels indicated in the characteristics of video cameras does not give an accurate idea of the resolution of the resulting image. The manufacturer indicates the number of pixels on the camera matrix (sensor), but not all of them are involved in creating the picture.

Therefore, the parameter “Number (number) of effective pixels” was introduced, which shows exactly how many pixels form the final image. Most often it corresponds to the real resolution of the resulting image, although there are exceptions.

IR (infrared) illumination, IR

Allows shooting at night. The capabilities of the matrix (sensor) of a video surveillance camera are much higher than those of the human eye - for example, the camera can “see” in infrared radiation. This property began to be used for filming at night and in unlit/dimly lit rooms. When a certain minimum illumination is reached, the video camera switches to shooting mode in the infrared range and turns on the infrared illumination (IR).

IR LEDs are built into the camera in such a way that the light from them does not fall into the camera lens, but illuminates its viewing angle.

The image obtained in low light conditions using infrared illumination is always black and white. Color cameras that support night photography also switch to black and white mode.

IR illumination values in video cameras are usually given in meters - that is, how many meters from the camera the illumination allows you to get a clear image. Long range IR illumination is called IR illuminator.

What is Smart IR, Smart IR?

Smart IR illumination (Smart IR) allows you to increase or decrease the power of infrared radiation depending on the distance to the object. This is done to ensure that objects that are close to the camera are not overexposed in the video.

IR filter (ICR), day/night mode

The use of infrared illumination for filming at night has one peculiarity: the matrix of such cameras is produced with increased sensitivity to the infrared range. This creates a problem for shooting in the daytime, since the matrix registers the infrared spectrum during the day, which disrupts the normal color of the resulting image.

Therefore, such cameras operate in two modes - day and night. During the day, the matrix is covered with a mechanical infrared filter (ICR), which cuts off infrared radiation. At night, the filter moves, allowing the rays of the infrared spectrum to freely enter the matrix.

Sometimes switching the day/night mode is implemented in software, but this solution produces lower-quality images.

The ICR filter can also be installed in cameras without infrared illumination - to cut off the infrared spectrum in the daytime and improve video color rendition.

If your camera doesn't have an IGR filter because it wasn't originally designed for night photography, you can't add night shooting functionality to it simply by purchasing a separate IR module. In this case, the color of daytime video will be significantly distorted.

Sensitivity (light sensitivity, minimum illumination)

Unlike cameras, where light sensitivity is expressed by the ISO parameter, the light sensitivity of video surveillance cameras is most often expressed in lux (Lux) and means the minimum illumination in which the camera is able to produce a good quality video image - clear and without noise. The lower the value of this parameter, the higher the sensitivity.

Video surveillance cameras are selected in accordance with the conditions in which they are planned to be used: for example, if the minimum sensitivity of the camera is 1 lux, then it will not be possible to obtain a clear image at night without additional infrared illumination.

Conditions	Light level
Natural light outside on a cloudless sunny day	over 100,000 lux
Natural light outside on a sunny day with light clouds	70,000 lux
Natural light outside in cloudy weather	20,000 lux
Shops, supermarkets:	750-1500 lux
Office or store:	50-500 lux
Hotel halls:	100-200 lux
Vehicle parking, warehouses	75-30 lux
Twilight	4 lux
Well-lit highway at night	10 lux
Spectator seats in the theater:	3-5 lux
Hospital at night, deep twilight	1 suite
Full moon	0.1 - 0.3 lux
Moonlight night (quarter moon)	0.05 lux
Clear moonless night	0.001 lux
Cloudy moonless night	0.0001 lux

The signal to noise ratio (S/N) determines the quality of the video signal. Noise in video images is caused by poor lighting and appears as colored or black and white snow or grain.

The parameter is measured in decibels. The picture below shows quite good image quality already at 30 dB, but in modern cameras, to obtain high-quality video, S/N should be at least 40 dB.

DNR Noise Reduction (3D-DNR, 2D-DNR)

Naturally, the problem of noise in video did not go unnoticed by manufacturers. On this moment There are two technologies for reducing noise in the picture and correspondingly improving the image:

2-DNR. Older and less advanced technology. Basically, only noise from the near background is removed; in addition, sometimes the image is slightly blurred due to cleaning.
3-DNR. Latest technology, which works according to a complex algorithm and removes not only near noise, but also snow and grain in the distant background.

Frame rate, fps (stream rate)

The frame rate affects the smoothness of the video image - the higher it is, the better. To achieve a smooth picture, a frequency of at least 16-17 frames per second is required. The PAL and SECAM standards support frame rates at 25 fps, and the NTSC standard supports 30 fps. For professional cameras, frame rates can reach up to 120 fps and higher.

However, it must be taken into account that the higher the frame rate, the more space will be required to store video and the more the transmission channel will be loaded.

Light compensation (HLC, BLC, WDR, DWDR)

Common video surveillance problems are:

individual bright objects falling into the frame (headlights, lamps, lanterns), which illuminate part of the image, and because of which it is impossible to see important details;
too much bright lighting in the background (a sunny street behind the doors of a room or outside a window, etc.), against which nearby objects appear too dark.

To solve them, there are several functions (technologies) used in surveillance cameras.

HLC - bright light compensation. Compare:

BLC - backlight compensation. It is implemented by increasing the exposure of the entire image, as a result of which objects in the foreground become lighter, but the background is too light to see details.

WDR (sometimes also called HDR) - wide dynamic range. Also used for backlight compensation, but more effectively than BLC. When using WDR, all objects in the video have approximately the same brightness and clarity, which allows you to see in detail not only the foreground, but also the background. This is achieved due to the fact that the camera takes pictures with different exposures, and then combines them to obtain a frame with optimal brightness of all objects.

D-WDR - software implementation of wide dynamic range, which is slightly worse than full-fledged WDR.

Protection classes IK (Vandal-proof, anti-vandal) and IP (from moisture and dust)

This parameter is important if you are choosing a camera for outdoor video surveillance or in a room with high humidity, dust, etc.

IP classes- this is protection against the ingress of foreign objects of various diameters, including dust particles, as well as protection from moisture. ClassesIK- this is anti-vandal protection, i.e. from mechanical impact.

The most common protection classes among outdoor CCTV cameras are IP66, IP67 and IK10.

Protection class IP66: The camera is completely dustproof and protected from strong water jets (or sea waves). Water gets inside in small quantities and does not interfere with the operation of the video camera.
Protection class IP67: The camera is completely dustproof and can withstand short periods of full immersion under water or being under snow for a long time.
Anti-vandal protection class IK10: The camera body will withstand a 5 kg load from a 40 cm height (impact energy 20 J).

Hidden areas (Privacy Mask)

Sometimes it becomes necessary to hide from observation and recording some areas that fall within the camera's field of view. Most often this is due to the protection of privacy. Some camera models allow you to adjust the settings of several of these zones, covering a certain part or parts of the image.

For example, in the picture below, the windows of a neighboring house are hidden in the camera image.

Other functions of CCTV cameras (DIS, AGC, AWB, etc.)

OSD menu- the ability to manually adjust many camera parameters: exposure, brightness, focal length (if there is such an option), etc.

- shooting in low light conditions without infrared illumination.

DIS- camera image stabilization function when shooting in vibration or motion conditions

EXIR Technology- infrared illumination technology developed by Hikvision. Thanks to it, greater backlight efficiency is achieved: greater range with less power consumption, dispersion, etc.

AWB- automatic balance adjustment white in the image, so that the color rendition is as close as possible to the natural one visible to the human eye. Particularly relevant for rooms with artificial lighting and various light sources.

AGC (AGC)- automatic gain control. It is used to ensure that the output video stream from cameras is always stable, regardless of the strength of the input video stream. Most often, amplification of the video signal is required in low light conditions, and a decrease - on the contrary, when the lighting is too strong.

Motion Detector- thanks to this function, the camera can turn on and record only when there is movement on the object being monitored, and also transmit an alarm signal when the detector is triggered. This helps save space for storing video on the DVR, relieves the load on the video stream transmission channel, and organizes notification of personnel about a violation that has occurred.

Camera alarm input- this is the ability to turn on the camera and start recording video when any event occurs: the activation of a connected motion sensor or another sensor connected to it.

Alarm output allows you to trigger a reaction to an alarm event recorded by the camera, for example, turn on the siren, send an alert by mail or SMS, etc.

Didn't find the feature you were looking for?

We tried to collect all the frequently encountered characteristics of video surveillance cameras. If you did not find an explanation of some parameter here that is unclear to you, write in the comments, we will try to add this information to the article.

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What kind of result can you achieve by switching to a camera with a larger sensor?

There have been many formats in the history of cinema: IMAX, Kinetoscope, Cinemarama, Cinemascope, Ultra Panavision 70 and so on. Among this variety, the most common is Super 35, which has not lost popularity among cameramen and directors since its appearance in the early 1980s.

Today, the industry is increasingly using large full-frame sensors measuring approximately 36 x 24 mm, although they can be slightly larger or smaller (but not going up to 65 mm).

Sometimes you hear questions: “What is the difference between Super 35 and full frame sensors? Which one is better? There is a completely precise answer to the latter: it is impossible to say which sensor is definitely better. All of them are just tools to achieve the goals of the authors.

Format, resolution, color depth, frame rate, lens and camera format are all just ways to tell a story. Some tools offer more options: for example, shooting in 4K allows you to significantly rework the image in post-production, make crops and change cropping, and RAW files are needed to expand the dynamic range for color correction. There is no general formula that would suit any painting - each project requires a special approach.

No director, DP or producer should choose a style simply because Sven Nykvist, Roger Deakins or Freddie Young shot in it. The choice of tools should depend only on your own vision and the conditions in which the shooting takes place. Learn to answer the following questions: “Why do I want to shoot with this camera/lens and in this resolution, why is low depth of field so important to me, why do I need a Steadicam, why is this particular frame format important to me?”

Determine what your story is about. Choose the format you like. You don't have to stick to one format throughout the entire tape. Don't be afraid to experiment with aspect ratio, resolution, lenses (prime and zoom, anamorphic and spherical), shoot on film and digital cameras. Don't worry, there are no strict rules in cinema. Well, okay, there is still one thing: the sound should be good.

And yes, there are situations when you won't have special choice, are possible. For example, Netflix requires 4K resolution for its projects. Or perhaps you're short on budget. But where you can still choose, you need to do it consciously. This way you will become better at what you do.

Full-frame and Super35 sensors perceive images differently. Both rely on the dimensions of classic 35mm film, but the full-frame sensors are larger than Super35. Hence the question: how are they fundamentally different from each other?

Lauren Simons, senior engineer at Canon Americas, has prepared a short demonstration that clearly shows the differences different types sensors using a Canon C700 FF camera and two lenses with different focal lengths: “Larger sensors give more space, which allows you to maintain an optimal pixel pitch while increasing the overall resolution.”

If you've never heard of the concept of pixel pitch before, it's the distance between the centers of adjacent pixels. The smaller the pixel pitch, the closer they are located to each other, the higher the resolution of the matrix - and vice versa. However, more a high resolution not always synonymous good quality Images.

To illustrate the differences between the different types of sensors, Simons mounted the C700 FF on a dolly cart and placed a girl in front of the camera against a dark canvas background.

As for the characteristics: the sensor size of the C700 FF is 38.1 by 20.1 mm with an image field of 18.69 megapixels (resolution 5952 by 3140), that is, 5.9K. the pixel size is 6.4 by 6.4 microns. Image cropping up to Super 35 occurs in the camera itself. It also has a Super 16 mode. Simons also used a Zeiss 28-80 mm T2.9 Compact Zoom lens. Thus, he tried to show the differences between different sensor formats as clearly as possible.

Canon C700 FF full frame sensor
Focal length: 48 mm
Distance between camera and subject: 2.4 m

Super 35
Focal length: 48 mm
Distance between camera and subject: 2.4 m

If you look closely at these frames, you will notice that the image captured using a full-frame sensor comes out much wider. Most likely, you already knew this. Simons explains: “The larger the camera sensor, the more space you scan and the more you will see in the final frame.”

But does this mean that when you shoot with a larger sensor you get a shallower depth of field? “Not necessarily,” Simons replies.

Take a look at the images below.

Super 35
Focal length: 48 mm
Distance between camera and subject: 2.4 m

Canon C700 FF full frame sensor
Focal length: 48mm
Distance between camera and subject: 2.4 m, 1.45x digital zoom

Note that the second frame has been digitally zoomed (1.45x) to match the dimensions of the first. The bokeh effect and compression remained unchanged. “The purpose of the comparison is to show that as the sensor changes, only the size of the scanned space changes. Other characteristics remain the same,” says Simons.

Now let's take a look at how a longer focal length affects images captured with different types of sensors.

Focal length: 70mm

Super 35
Focal length: 48mm
Distance between camera and subject: 2.4 m

Here, the full-frame image was shot at a focal length of 70 mm, and the Super35 at 48 mm (with the model at the same distance). The framing remains identical, but the bokeh effect is much more noticeable and the depth of field is shallower. Simons explains: "There is no direct influence sensor size. A larger sensor has a larger field of view, and so we tend to zoom to keep the same framing. Therefore, the depth of field is less.”

In the next pair, Simons did not use the zoom, but moved the camera closer to the model.

Canon C700 FF Full Frame Sensor
Focal length: 48mm
Distance between camera and subject: 1.8

Super35
Focal length: 48mm
Distance between camera and subject: 2.4 m

There are several interesting details you can notice here. Firstly, the framing turned out to be almost identical. Secondly, the depth of field in both images is almost the same: it is slightly lower in the full-frame version. This can be explained by the shorter distance between the camera and the subject, which brings us closer to the minimum focal length of the lens.

“The most important differences are visible in the foreground and background. The full-frame image shows more spots of light cast by the light bulbs at the top and bottom of the frame. Take a closer look at the green lamps below and the yellow and blue ones above. The second image does not show the light fixture in the top left corner of the frame. The opposite situation occurs with the foreground. Here we see less on Super35,” explains Simons.

Simons even came up with a name for this phenomenon: “The Survivor Effect.” That's right, it's in honor of the film by Iñárritu and cinematographer Emmanuel Lubezki with Leonardo DiCaprio in leading role. In short, changing the camera position results in the foreground being closer and the background being further away. Therefore, the frame comes out deeper and more spacious.

Keep in mind that this experiment was conducted using a Canon C700 FF and Zeiss lenses. It is impossible to say exactly how ARRI, RED, Sony and Panasonic devices will behave in similar conditions. But now you have an idea of how the sensor formats differ.

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