Ways to think about ISO

ISO, sensitivity, gives you the ability to shoot at high shutter speeds, but at the expense of quality. It is therefore important to choose judiciously. Hence this post.

There are several ways to think about ISO, and I thought I would run them by you again in these dark days of December (and I added “Studio”, as per reader Ray’s suggestion):

1. By absolute starting points:

  • Outdoor: 200
  • Indoor: 400 (but in a studio, 100)
  • Difficult light: 800

And you go up if and as needed, and down if able.

B. Simple, by situational starting points:

  • Normally, outdoors: Auto
  • When using a tripod: 100
  • When in bright conditions: 100
  • When in a studio: Indoors: 400
  • Sports, night clubs, museums: 800-1600

C. By consequences:

  • Motion blur: Increase the ISO.
  • Shooting art, or for a magazine, or in a studio, or for large prints: decrease the ISO.
  • Getting very fast shutter speeds, faster than you need: decrease the ISO.

By understanding those three lists, you will be able to choose the right ISO at the right time. And that is an essential if simple part of making a good picture.

6 thoughts on “Ways to think about ISO

  1. I’m a little confused by Part C. When you list your “consequences” you suggest raising ISO to avoid motion blur (which makes perfect sense to me) but then you suggest lowering ISO to get a fast shutter speed. Wouldn’t a faster shutter speed mean less light getting to your senros thus requiring a higher ISO? Isn’t this the reason why higher ISO helps avoid the motion blur — because you can shoot at a faster shutter speed without being left with a dark image?

    Help this rookie understand. 🙂

    • I was in too much of a hurry, Ed. What I meant to say was: when see see you are getting fast shutter speeds, faster than you need, you can decrease the ISO to a lower setting. I merely implied the first part, instead of stating explicitly.

      E.g. if I am shooting a museum full of statues and I see 1/4000th second, I can safely decrease the ISO to a very low level, since I do not need 1/4000th second for statues.

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