When I had a film camera I bought 200 ASA Fuji film. I loved the color of fuji and I mostly took outdoor photos. (At some point I probably should have switched to slide film for better prints, but it was expensive, took longer to get back, and you had to view with a slide projector or loop.) If you knew you were going to be shooting indoors for a wedding or something you might buy a roll of 400 ISO. Now with digital you can change the ISO for every shot if you want to.
A good explanation of what happens when you turn up the ISO on your camera can be found on the dpreview.com website.
A more detailed explanation of noise can be found here.
I noticed that some of my friends that photograph birds (they’ve got 400mm lenses) use a really high ISO. This “freezes” the movement, and gives them sharper shots of the birds in flight (on some shots the details on the feathers is amazing). Their pictures are really beautiful and sharp. I was wondering why that worked out so well for them since I always thought of higher ISO as letting you shoot in lower light, but also being grainier. Sometimes the graininess was artistic looking, but mostly it just looked bad.
When I bought my camera I just set the ISO to 200 since that is what I knew from film (and as I noted earlier, there was a lot to be learning with a new camera). I decided it was time to try some experiments. While on the Yosemite trip I set up my tripod and did some tests.
I set the camera up at a stream and tried a few shots at different ISO’s. I wanted something moving so I could see how the ISO was helping capture a moving object. The stream probably wasn’t perfectly constant for you purists out there, but it was perfect for what I wanted to see.
I shot a series at every ISO setting (I’m just showing 100, 400, 800, 1600, and 3200 above) I was thrilled to see that the texture of the water got sharper as I raised the ISO. The whole photograph has a lot of texture in it and I didn’t see any grain in these shots until about 1600 ISO (which I would never have considered shooting at anyway).
I did another set (you can see a comparison of 400 and 3200 at right). This series was of a rock formation with a lot of sky in the frame. The sky showed some grain at the 400 setting, but it was a level I was OK with. After that the sky quickly deteriorated.
I noticed that up to a point I liked the sharper images. Normally you don’t want to freeze water – it’s prettier when it is soft and blurry looking – but I got to see how the ISO changed things in a controlled setting. I will probably keep experimenting with this. I have moved my ISO up to 320 for most shots. When I had it at 400 I kept forgetting to lower it when there was a lot of sky in the shot. So for now I’ll keep it at 320 for handheld shots and move it up for specific situations. I’m keeping the ISO low for tri-pod shots because the lower ISO does have the best quality (and hopefully my camera isn’t moving on the tripod)!
Dear Reader: I’m interested in how you do things, please share!
What kinds of results have you gotten playing with the ISO settings?