ISO (Exposure Series Part 5 of 5)
The higher the number the more sensitive the image sensor is and the less light it needs to create an image. The lower the number the less sensitive it is and more light will be required. ISO setting follow a standard sequence, a typical range:
100; 200; 400; 800; 1600; 3200
Effects of ISO
Normally, you might increase or decrease your ISO when the other parts of the exposure triangle don’t allow you to achieve proper exposure for the desired effect you are after.
Most photographers shoot with the lowest ISO possible (many DSLR cameras start at ISO 100 or 200). This is because the higher the ISO becomes, the more grain and digital noise get added to your image (see example below).
Situations where you might need to increase your ISO to capture the scene.
Note: These are situations where flash is an undesired option because you don’t want to disturb the mood, or the subject is too far away for the flash to be effective, or for creative decisions.
What about the grain/noise?
Through experience you will learn to make decisions regarding ISO settings. Some questions to ask yourself:
Increasingly as technology advances cameras are getting better and better at handling noise, even at higher ISO settings. Proper exposure also plays an important role in keeping unwanted image noise at bay. An underexposed image will usually have more grain and digital noise than a properly exposed image. Other factors such as extreme heat can effect the noise. In post-processing, recovering shadow areas by extreme changes to bring out detail will sometimes bring out noise too.
There is software available that will help reduce the noise. I use Noise Ninja for most of my work, or the built in Noise reduction in ACDSee Pro. I didn't post it here, but as a test I ran Noise Ninja on the ISO 3200 image above, the results was an image that looked more like the ISO 800 version. Noise reduction software works! Some other programs that reduce noise:
So, what do you do to reduce noise?
If your camera has it, do you use Auto ISO?
How do you decide your ISO setting?
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