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ISO - Exposure Triangle Part 3

Blonde model holding camera - Explaining ISO as part of exposure triangle

In old film days, camera films were available in different ISO or ASA ratings. The rating denotes how much sensitive the film is to the light. Higher rating means the film is more sensitive to light and it will amplify the light which hits the film, lower rating denotes it is less sensitive to the light and it will not amplify light as in higher rating films. From this, you might think films with higher ISO is always better but the higher amplification comes with a significant cost which leads most photographers to use lowest ISO possible in most conditions. We will discuss that in a bit. For starter, ISO Stands for International Standard organization and ASA stands for American Standards Association, Since the late 1980s, photographers no longer use ASA for film sensitivity and ISO became more predominant all over the world. For your information, there is no difference between ISO and ASA, both are standards developed by International Standards Organization.

In modern digital cameras, you can change the sensitivity of camera sensor (ISO) by pressing few buttons without any difficulty. The lowest ISO rating is 100 (some offers 50 also), and the highest varies between manufacturers to manufacture but it is generally around 6400 to 12800 or even higher. At high ISO ratings, the sensor will be more sensitive and you can take well-exposed pictures in poorly lit rooms and in dark areas; the sensor will capture more light to balance the darkness. This is the advantage of increasing ISO, but it comes with a disadvantage; Noise.

Noise is a big headache for all photographers, if you do not know what is noise, it is the grainy look which you see in photographs when you have zoomed into 100%. If you have taken any picture with your smartphone, open it and zoom into 100% and you will see dotted grains all over the picture, it is called noise. Noise significantly affects the quality and color of your photographs. The noise is so problematic that many photographers exclusively shoot in ISO 100 unless they are in a situation where they don't have absolutely any means to increase the exposure (Cannot add light to the location or cannot modify aperture/shutter speed).

If you have a smartphone or compact camera, increasing ISO will significantly deteriorate image quality that even shooting at ISO 200 might give you a grainy look. But, high-end DSLRs can produce superior quality images even at ISO 800. Many smartphones and compact cameras won't even have the option to change the ISO. They will be set to Auto.