ISO settings in digital photography

Original author: Darren Rowse
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Grant (reader of the DPS site) asks: “ I got confused about photosensitivity (ISO). Which value is better to choose? Better to choose the lowest? "

Thanks for the question, Grant. Before I try to answer this question, let me give a little definition of ISO.

What is ISO?

In traditional (film) photography, ISO (or ASA) shows how sensitive the film is to light. It is measured in numbers (you probably saw them on boxes with films - 100, 200, 400, 800, etc.). The smaller the number, the less the film is susceptible to light and the smaller the graininess in the resulting photographs.

In digital photographyISO measures the sensitivity of the camera sensor. The same principles apply here as in film photography - the smaller the number, the less the film is susceptible to light and the less granularity will be. High values ​​of photosensitivity are used mainly in situations with insufficient lighting, when it is necessary to use a short shutter speed (for example, if you shoot sports events indoors and want to “freeze” the movement) - nevertheless, you will have to pay for it with noise. I will illustrate this below with two fragments of photos - the left is shot with a sensitivity of 100, the right is 3200
image
(you can see larger versions of each of the photos: ISO 100 and ISO 3200 )

ISO 100 is considered a 'normal' value and will make your photos clear (reduce noise / grain).
Most people continue to shoot in automatic mode, where the camera itself selects the sensitivity value, depending on the situation in which you are shooting (the camera will try to make it as low as possible), however, most cameras provide you with the opportunity to choose the sensitivity value yourself.
If you do not agree with the settings offered by the automation, and set the photosensitivity value yourself, you will see how this affects the aperture and shutter speed. For example, if you increase the ISO from 100 to 400, you will notice that the shutter speed and / or aperture gap will decrease.

When choosing photosensitivity, I usually ask myself the following four questions:

1. Light- Is the subject sufficiently lit?
2. Grain - Do I need grain or do I need a picture without noise?
3. Tripod - Am I using a tripod?
4. Object movement - Whether my object is moving or resting in place.

If there is enough light around, I want to get a little grain, I use a tripod and the subject does not move, then I usually use a rather low value of photosensitivity.

If it is dark around, I intentionally want to get grain, I shoot without a tripod and / or my subject moves, I will consider increasing the sensitivity value, which will allow me to use lower shutter speeds and at the same time get good pictures.

Of course, in return we get more noise in the picture.

The following are situations in which you may need to increase the value of photosensitivity:

Indoor sporting events - where your object is moving fast and there is also a lack of light.

Concerts - where there is also little light and often you can’t use a flash there.

Galleries, churches, etc. - many galleries are against the use of flashes and, of course, there is a lack of light in the room.

Birthdays - the moment of blowing out the candles can give you a picture with a pleasant mood, which will be ruined by the flash. An increase in ISO will help you catch the moment.

Light sensitivity is an important aspect in digital photography, a must if you want more control over your camera. So experiment with the settings and how they affect your photos!

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