Besides adjusting aperture and/or shutter speed, ISO sensitivity is extremely helpful in different light conditions. The higher the ISO sensitivity, the less light needed to make an exposure, allowing higher shutter speeds or smaller aperture. This is especially true when in low light environment. The ISO setting on my camera ranges from ISO 100 to ISO 3200, and higher.
Let me show you what I am talking about. All pictures were taken with f/7.1, the camera adjusted the shutter speed automatically when I changed the ISO sensitivity setting.
ISO 100, 1/15
ISO 200, 1/20
ISO 400, 1/40
ISO 800, 1/100
ISO 1600, 1/250
ISO 3200, 1/500
Noticed how as the ISO sensitivity goes up, the picture looks darker?
My man and I went plant-shopping today. We got several houseplants in addition to the several plants I got already. And now we live in a greenhouse. This is a neon pothos. I love the bright green color.
Remember the birthday flowers I got two weeks ago? I was sad to see the calla lilies turn brown, but I save the roses. They are sitting on my kitchen counter slowly drying up.
All pictures were taken at f/5.
ISO 3200, 1/13
ISO 1600, 1/5
ISO 800, 1/2.5
ISO 400, 1/1.6
ISO 200, 1.3
This time I started the ISO sensitivity from the highest setting until the shutter speed was 1.3s. I did not use a tripod at the time that was why the pictures were blurry at lower ISO settings. Also, the bigger ISO sensitivity, the "grainer" your picture will look. Try zooming all the way on a picture with taken with a high ISO sensitivity.
This is what I love about SLR camera, there is endless possibilities of different settings. Playing with ISO sensitivity is only one of them, but I did learn something easy that could change how my pictures turn out.