ISO sensitivity- a characteristic of a digital camera that determines the sensitivity of the sensor to light. It is expressed in ISO units, which were adopted in film photography and were transferred to digital for convenience.

The importance of light sensitivity lies in the fact that with the help of this parameter it is possible, without changing ( and ), to adjust the brightness of the frame (Fig. 1).

Rice. 1 - Adjust the brightness of the image using the ISO value

Technically, this is done by pre-amplifying the electrical signals of the photosensitive matrix and algorithms for their subsequent analog-to-digital conversion into the color space of the camera, mainly sRGB. Those. in fact, with an increase in the ISO value, the photosensitivity of the photocells does not increase, but the light produced in them increases. electricity. As a consequence, with an increase in photosensitivity (Fig. 2).

When to Raise the ISO Sensitivity

To obtain high-quality images, the ISO value should be raised only when it is impossible to shoot with a given exposure under the given conditions. For example, shooting indoors without a flash, shooting in a dimly lit area (evening, night shooting near the flashlight), shooting on

The maximum sensitivity of ISO 204800 was implemented in Canon EOS 1D X cameras in 2011 and Nikon D4 cameras in 2012.

Rice. 2 - The appearance of digital noise when increasing the ISO value

Optimum ISO sensitivity

ISO sensitivity is selected for each specific situation and it is desirable that it be as low as possible.

Optimum ISO sensitivity chosen in practice. To do this, you need to focus on the expected exposure, at which there will be no (for example, in the evening when photographing with a lens with focal length 50 mm, shutter speed should not drop below 1/50 s, aperture, if possible, open f1.8). In this case, with a fast lens, the optimal ISO value will be 200, provided that the frame is sharp and not blurry. Obviously, in the case shown in Fig. 2, the optimal ISO value is 500. The exposure in this case (f4.0 1/50 s) provided a blur-free and sharp frame in the given conditions.

In sports shooting, you need to focus on shutter speed (1/640 s), and the optimal ISO value will be one that can provide such an exposure.

The table below describes the approximate optimum ISO values ​​under different conditions.

Table 1 - ISO sensitivity

		Application
		Photographing in daylight, in the studio, with flash. Any photograph where a stable tripod can be used.
		Used in low light, using a shutter speed that allows safe handheld photography. In this case, an open aperture is often used. It is also used to increase the effective flash range.
		Handheld photography in the worst lighting conditions, when the flash is not used or it is not enough.

By doubling the ISO value, the amount of light needed to create a properly exposed image is halved. This means that when going from ISO 100 to ISO 200, you can use half the shutter speed or increase the f-number by one stop. By changing the sensitivity from ISO 100 to ISO 1600, you can use a shutter speed 16 times faster or reduce the aperture value by the same amount.

With the development of science and technology, new hardware and software appear, new sensor manufacturing technologies open up, new materials come to replace the previous ones, and all this in total leads to an improvement in the quality of photographs.

Light sensitivity (ISO)- the sensitivity of the camera matrix to the amount of light received. Exist different meanings ISO. In modern cameras, the sensitivity can be adjusted independently, depending on each specific situation.

Impact on noise

Noise is a distortion in an image, representing gray and white dots. The higher the light sensitivity level, the more noticeable the noise will be; the inverse proportionality is also true: the lower the ISO, the less pronounced the noise in the photo. The highest quality images are obtained when shooting at low ISO values: 50, 100, 200.

Why do noises occur? Increasing the sensitivity is, in fact, amplifying all the signals received from the pixels. When an electrical signal is amplified, extraneous signals, that is, interference, are also amplified. The larger the camera matrix, the less noise occurs.

With what ISO to choose a camera?

When choosing a camera, remember the following recommendations:

• Pay attention to the maximum and minimum possible ISO values;
• Do not chase high ISO values, because they are unlikely to be useful to you in practice, since a large ISO leads to poor quality photographs;
• Do you still want the ISO on your camera to be high? Pay attention to professional and semi-professional cameras. The large size of their matrix reduces the amount of noise in the photo;
• Worst of all with interference is the situation on digital soap dishes. If on reflex camera ISO 400 is quite possible to work, then noise is already beginning to appear on digital cameras at the same indicators.

How to set ISO?

At self setting ISO, use the following tips:

• Shooting should be done at the lowest possible ISO values. Raise the level of photosensitivity should be only in the most extreme cases;
• At low ISO values, the shutter speed is too long for handheld shooting;
• If you want to set the lowest ISO value, open the aperture as much as possible, the inverse proportion is also true;
• You should not set a high ISO level if the flash is on on the camera;
• To decrease the shutter speed, it is necessary to increase the photosensitivity, and the inverse proportion is also true.

High and low ISO

Features of cameras with an extended ISO range:

• When expanding into a high sensitivity range, that is, on cameras with a higher ISO , the effect of noise will be very noticeable in the pictures. Buying such a camera is most often completely pointless, unless you are printing photos in small sizes, on which the noise is not so visible;
• When expanding to a low ISO range, it becomes possible to work at slower shutter speeds. The image noise level is greatly improved. At the same time, the contrast of the photo is lost.

When is a high ISO required?

• Sports events, holidays for children, where shooting is done at a short shutter speed, otherwise there is a high risk of getting blurry photos;
• Opening day, church, theatre, exhibition, and any other place where flash is prohibited;
• Shooting various meaningful moments: a kiss, blowing out candles on a birthday cake. A flash can spoil the impression of these memorable moments.

How to measure ISO?

Light sensitivity is usually measured in ISO units, its standard values ​​are: ISO 100, ISO 200, ISO 400 and so on. Each successive value doubles the sensitivity. In expensive cameras, there are intermediate levels of ISO. IN automatic mode sensitivity values ​​can be any, including intermediate ones. High ISO values ​​are used when there is insufficient light. This way you can take a picture at a faster shutter speed.

Auto ISO

The automatic ISO setting in the camera, as the name implies, sets the optimal ISO values ​​​​in automatic mode. This function is extremely convenient, because the pictures have to be taken at different lighting conditions, and constant wandering in the settings does not contribute to open creative impulses.

However, the automatic ISO setting has its downsides. When setting parameters, it does not take into account the consequences high level photosensitivity. As a result, photos with increased noise are obtained. You can deal with the problem if you have a camera with an ISO limiter. It allows you to set the maximum possible meaning ISO.

Conclusion

In essence, one thing you need to know about ISO: the higher the ISO, the lower the quality of the photo, but in some cases it is difficult to do without high ISO values.

To get the highest quality pictures that a camera can allow, you need to understand such a concept as ISO sensitivity. The article is intended for beginner photographers, so we will try to consider this topic clearly and simply.

ISO sensitivity - what is it?

Back in the days of film photography, someone will remember how they selected film for shooting indoors and for shooting outdoors. The main selection criterion was the light sensitivity of the film. Film sensitivity 200 Suitable for shooting outdoors good lighting. But for the apartment, a film with a sensitivity of 400 was needed.

talking plain language, ISO- this camera sensitivity to light. The lower the ISO value, the less sensitive the camera is to light, and the higher the ISO value, the more sensitive the camera is. The sensor is responsible for changing the sensitivity of the camera (that is, the camera matrix). This is the most important and expensive part in the camera, which collects the light and turns it into an image. At high ISO values, we can capture an image in low light conditions without using a flash. But, depending on the level of the camera, we get noises(grain in the image).

For clarity, look at the image below:

Therefore, noise is very noticeable at high values.

ISO values ​​in modern cameras: 50 , 100 , 125 , 160 , 200 , 250, 320 , 400 , 500, 640, 800 , 1000, 1250, 1600 , 2000, 2500, 3200 , 4000, 5000, 6400 , 8000, 10000, 12800, 16000, 20000, 25600

Effect of ISO on exposure

We have already covered how aperture and shutter speed affect exposure in previous articles. Now, in order to understand how ISO sensitivity affects exposure, consider photos taken at the same aperture and shutter speed, the lighting did not change during the shooting.

f 1/8 1/320 ISO 100 shot indoors during the day

By increasing the ISO value, we help the camera sensor capture more light. With each higher ISO value, the image becomes lighter.

Effect of ISO on image quality

As mentioned above, the higher the ISO value, the more noise and artifacts are obtained in the photo. Detail is also reduced, colors become dimmer. In converters, you can always carefully smooth out the noise, but the quality will remain at a low level anyway.

ISO values ​​for various shootings

The ISO setting is usually the first thing to set up on the camera as soon as we are about to shoot something.

ISO 50-200 suitable for shooting outdoors during the day. You can of course put more, but do not forget about the quality.

f 2/8 1/500 ISO 200

ISO 400-800 is more suitable for shooting in a well-lit room, or outdoors in sunset lighting.

f 1/8 1/500 ISO400

ISO 800-1600 for shooting in a dark room where the flash cannot be used

f 1/8 1/100 ISO 1600

ISO 3200 and above is suitable for shooting the starry sky or the milky way

What to be guided by when installing ISO

1. Pay attention to the light, whether it is enough or not.
2. Are you going to use the flash or not
3. Will shooting with a tripod
4. Is it allowed in the photo digital noise.
5. The scene will be dynamic or static.

Conclusion

Try to always shoot minimum values ISO. Open the aperture as far as the depth of field allows. If you are using a flash, do not set too much great importance ISO, average 800 more than enough.

And most importantly, experiment more!

ISO is the light sensitivity of your camera, or rather, the sensitivity to light perception of the camera matrix. That is, if the ISO is 200, then less light will enter the sensor per unit of time than in the same time with a ISO value of 3200. The higher the ISO sensitivity of the sensor, the clearer pictures you can take, but you should not assume that clearer pictures it's always good. The more ISO you can set on your camera, the more extraneous noise appears in your pictures.

The standard ISO values ​​​​are: 100, 200, 400, 800, 1600, 3200. And the noise that appears in the pictures is multi-colored bright points in the photographs, which are very different in color from the neighboring ones. This noise makes the image look like it was taken with a 0.3 megapixel camera on a 2006 phone.

However, the ISO system was created for film cameras. IN digital cameras this parameter seems to correlate with the obtained exposure of the pictures on it and similar characteristics of the film camera. Therefore, this parameter on digital cameras has completely become known as "equivalent ISO speed". And it is expressed in ISO units for a film camera for the convenience of photographers.

How to use light sensitivity correctly

If you are photographing in a lit place, where enough light can get on the camera matrix in a short amount of time, then you should set the ISO to a small mark. If the room is dark, or you are shooting late in the evening, then the ISO value should be many times higher. However, it is always worth taking a few test shots and finding the best solution.

Do not forget that for shots at night, it is important to open the aperture so that more light can also enter the camera's matrix. If you are working with a tripod and static objects, then it is better to set the minimum ISO, but increase the camera's delay. If you want to reduce the amount of noise in your pictures, you can also use a flash to add light to the photo.

Setting the sensitivity also depends on the size of the matrix of your camera, if you have a fairly simple camera without interchangeable lenses, then the most beneficial value for you is ISO 800. If you set this parameter higher, then any photo will be overwhelmed with unnecessary noise. On the SLR cameras who have best options shooting, ISO 1600 and 3200 can be used.

Instead of the name ISO, they often say ISO. This name better describes the purpose of this parameter. ISO is a measure of how sensitive it is to the light it's exposed to. More high value ISO makes the sensor more sensitive to light, so higher values ​​are used for shooting in poor lighting conditions. Modern digital cameras can take pictures at different ISO settings, which will be recorded on a single memory card. In the past, photographers had to change film to change the ISO value.

When should you raise your ISO? For example, the camera cannot build a normal exposure. The lighting is too weak for him. Sometimes you can use the flash, but this does not always help. For example, when shooting at a concert, it is not always possible to use the flash and it will not always help. In this case, you need to increase the ISO manually or set the mode automatic selection photosensitivity.

Increasing the ISO makes it possible to decrease the shutter speed. This will help to get rid of movement or allow you to take normal shots in cases where a tripod would be needed with a lower ISO value.

Noise and ISO.

Increasing ISO is not only positive character, but also negative. Increasing the sensitivity to light inevitably leads to the appearance of noise in photographs. This is caused by. that the matrix, together with the useful light signal, begins to perceive minor interference and distortion. In addition, the matrix itself does not transmit a 100% perfect image. Increasing the sensitivity to light increases the errors that are caused by leakage currents between pixels.

All sensors are adjusted in such a way as to transmit the least amount of noise at the lowest ISO values. In most cameras this is ISO=50, 80 or 100.

Noise in digital photos is similar to grain in film photos. This effect is highly undesirable. It appears as colored dots that are distributed throughout the frame.

Relationship between ISO and matrix size.

The physical size of the matrix determines the quality of the images that will be obtained at certain ISO values. This is primarily due to the fact that pixels on large matrices are larger than on small ones, and therefore they perceive more light. For example, two 4 megapixel sensors with different sizes at the same settings will show different noise results. The larger matrix will make less noise.

Is it possible to take pictures at high ISO.

Until all cameras are equipped with large sensors, the noise in the pictures will be very noticeable, and therefore will be a problem.

Relatively recently, cameras that are called semi-professional have appeared on the market. They have matrices bigger size than the compacts. Such cameras will have a lower noise figure, but only if the number of megapixels is not too high. Don't be fooled by ads that say more megapixels is better. This is not true. Everything should be in moderation.

Slight noise will not be noticeable in pictures if they are printed small. Exist special programs and plugins for Photoshop, which significantly remove noise from images. Among such programs are: Noise Ninja, Neat Image and many others.

There can often be situations where the choice is between taking a photo at a high ISO or not taking a photo at all. In this case, it is better to take a picture and try to remove the noise on the computer. Also, not all noisy shots look bad.

Conclusions.

• ISO is a parameter that determines the camera's light sensitivity.
• The best pictures are obtained at the lowest ISO value. In order to make sure that it is worth the most small value, you need to switch to manual mode and make sure of this.
• When shooting indoors under poor lighting conditions, the choice to use the flash or studio lighting or increase the ISO value. Different cameras will show noise differently. The degree of noise depends on the size of the matrix.
• Matrices with large physical size will allow you to shoot at a higher ISO without losing quality. In addition, this will reduce the shutter speed and thereby get rid of the shake and blurry photos.
• When printing photos in small sizes, the noise is almost imperceptible.