What is ISO?
ISO numbers measure how sensitive the sensor is to light. The lower the number the less sensitive (100 – 400) and the higher the number the more sensitive to light (800, 1600+).
On a bright sunny day, you will have your camera set at 100. As things get darker, in the shade, inside, low lights, you will raise your ISO to make up for the lack of light.
Below you will see exactly how light is affected when changing your ISO. I left all of my other settings the same except for my ISO so you can clearly see the difference. In this situation, I would shoot with my ISO around 400.
As a result the higher the number the more noise you get in pictures. Noise is the grain that you see in pictures at times. So to avoid noise keep you ISO as low as you can get away with. With most camera’s 400 and under and you wont notice a noise level. Nikon’s are known for having a little less noise in low light. But overall both brands are amazing.
Some things to consider when choosing your ISO:
Do you have good light?
Do you want noise in your picture?
Are you using a tripod? You can get lower ISO number if you subject is stationary and can have slower shutter speeds.
If you are in a dark setting, and you need your shutter speed to be faster(shutter speed is our next topic) you’ll need to raise you ISO.
Indoor sporting event – Subjects are moving fast, and there is limited light available.
No Flash Zones- Plenty of shows, recitals, galleries where you can’t use flash you’ll need to have a higher ISO
Birthdays – Blowing out the candles, don’t use your flash, keep the mood and crank up the ISO.
Below I have a sample from a lower end DSLR and a Higher End DSLR. A Canon t2i has an ISO range from 100-12800. An entry level DSLR will show a larger amount of noise. As you can see at ISO 100, you have a very clear image and at 3200 you can see the noise. When you take a picture don’t just trust your LCD screen, zoom in and check your noise if you are worried.
With a 5D Mark III you can see how minimal the noise is even at ISO 8000. The 5d Mark III has an ISO range from 100-25600.
*For you Nikon peeps out there, a Canon t2i is comparable to a nikon D90, a T3i to a D5100. A Canon 5d mark III to a Nikon D800.
ISO, Shutter Speed, and Aperture all play off each other. Part of whats called the EXPOSURE TRIANGLE, they all go hand in hand. However, you need to learn each one individually before we can throw everything at you. Next time I will be teaching you about Shutter Speed.