What is ISO in photography

You may have already come across ISO in business terminology. There it stands for International Organization for Standardization and means a kind of international and independent codex of company processes.

Referring to a camera, ISO means standards of measurement. Globally speaking, it’s an apparatus’s sensitivity to light.

There are three major ways to adjust your pic’s brightness: changing aperture, shutter speed and ISO. Some photographers consider that these three parameters make an Exposure Triangle. Others argue that while aperture and shutter speed brighten the image physically, letting more light in a cam, ISO just brightens a taken picture, hence, can’t be included in exposure.

There are also debates over the definition of ISO. While some specialists define it as a camera light sensitivity, others affirm that it is more like a mapping which tells the gadget how bright the photo should be.

What does ISO really mean? For us, the finest technical details are not important. We should just keep in mind that this setting is responsible for the brightness.

ISO values

If you still use photo films, you know that ISO is already marked on a cassette. The usual numbers are 100, 200, 400, 800, etc.

Digital cams, of course, don’t have ISO preset, you can adjust this parameter either in auto or in a manual mode.

Every cam has its base ISO ­— usually it’s very low, 100 or 200. But you can increase it up to 3200 or even 6400, depending on the model’s settings. Those numbers don’t mean ISO speed, as there is no any, rather the brightness level.

Low ISO vs high ISO

Here we must remember the principle “Every action has a reaction”.

High ISO makes a picture brighter, but it also makes it “noisy” or “grainy”, revealing all the tiny film imperfections or, in a case with a digital pic, visual distortions.

The common recommendation: use low ISO whenever it’s possible, as there are other ways to control the brightness:

  1. Additional lighting and flash.
  2. Lower shutter speed. But be cautious ­— it’s applicable only for still objects and you’d better use a tripod, otherwise an image will be blurred.
  3. Wider aperture. Mind that this parameter also influences the depth of field, i.e. if you need a sharp and “in focus” background, aperture should be relatively narrow.
  4. Post-filming editing: you can adjust brightness, saturation, contrast and other parameters.

When do you need high ISO

When you can’t avail of above mentioned tips. For example:

  • In churches, museums, theatres, and other dark indoor spaces where you can’t use a flash.
  • When shooting sports events, concerts and festivals, where you can’t ask a model to take a pause and not to move for a while.
    • Sport event ISO example
  • When shooting wildlife: flying birds, running animals, etc.
    • Flying bird ISO example