Dumb question: Which ISO do you normally shoot at?

Here's a newbie question,

I usually shoot at lowest possible ISO to obtain the least noisy images. So, unless I want super-fast shutter speed, I am shooting ISO 100 (on my 30D) when I'm outdoors. Indoors, I use ISO 1600 if I don't happen to have a flash attached. Am I doing this right?

What ISOs do you normally use, and why?

Outdoors I use ISO160 as it is always dull up here.

Indoors with flash ISO400

Without flash, ISO1250-3200

Umm 400 most of the time is what I need to shoot outdoors with my 100-400mm @ F5.6.

I normally go with high ISO so that I can maximize shutter speed, since I shoot handheld 90 percent of the time. Even with IS lenses, I like to get as I usually try to get faster than 1/500 and prefer to go above 1/1000 if possible. I also only go for major backgroud blur about 40 percent of the time, so I commonly shoot at apertures between 5.6 and 11, even though I am mainly a portrait photographer. I prefer to deemphasize the background in post with fading, desaturation, and/or burning - on occasion creative blurring.

So, I commonly shoot ISO 400 or higher in blinding daylight, on occasion going as high as ISO 1600. Same indoors, but I usually back off a lot on shutter speed and somewhat on aperture, depending on subject and conditions.

bbbig,
I always have my cameras set at ISO 100 (yes sometimes I forget) and only bump it up as I need it. I don't set a standard except to always strive for ISO 100 even when using flash. Obviously this isn't always possible and then I bump it up as needed.

Oh and its not a dumb question

I use 100 or 200 outdoords, depending on the situation, and indoors I use 800 and 1600, with and without flash.

Indoors, even with flash, since I never use a tripod, I like to use ISO 1600 because it brightens up the background a lot more when shooting people...of course I have to deal with noise all the time..but hey, what's Neat Image for?

Oh, one more thing...

Since this is my first DSLR, and I've only had it since March...but I've had digital cameras (P&S only) for over 11 years, I'm no longer afraid of using high ISO's...

I'm from the old school where slower ISO film speed meant less noticeable grain in the finished image so I always had used ISO 25, 50, 64 and 100 film.

Today I carry this habit over and use ISO 100 all the time for less noise.

deltroid wrote in post #4005964
I use 100 or 200 outdoords, depending on the situation, and indoors I use 800 and 1600, with and without flash. [...]

Same here.

ISO 800. I love not having camera shake or noise with the mk III

Outdoors I have my ISO set between 100-200.

Indoors I bump it up to 400 to 800 (depending on if I'm using a flash or strobes).

BSBXTi wrote in post #4005911
Umm 400 most of the time is what I need to shoot outdoors with my 100-400mm @ F5.6.

me too - and with the new 40D, I've just set the ISO to automatic - it seems to choose 400 most often as well.

Naturalist wrote in post #4006020
I'm from the old school where slower ISO film speed meant less noticeable grain in the finished image so I always had used ISO 25, 50, 64 and 100 film.

Today I carry this habit over and use ISO 100 all the time for less noise.

I do the same for the same reasons. There are a lot of times when I wish 25/50 was available on the 20D.

nburwell wrote in post #4006126
Outdoors I have my ISO set between 100-200.

Indoors I bump it up to 400 to 800 (depending on if I'm using a flash or strobes).

Outdoors is set for 100, sometimes 200 depending on available light and indoor varies.

ISO 100 here as well.
I only boost it as needed...
I don't have any rules for setting ISO's indoors or outdoors.

I read something interesting and convincing on the web recently, but I just cannot find the link now. The upshot was, as I recall, that noise does not increase linearly (technically, monotonically) with ISO, but rather, there are periodic dips to lower noise than would be expected with a linear relationship. On most cameras, these dips are at ISO 100 200 400 800, etc. The explanation given was that these were the "real" sensitivities, while the intermediate settings being derived mathematically. Now - the interesting part is that for the 30D, these were at 160, 320, 640, 1250, etc.
I was convinced. I tend to use these steps now. I'll try to find the link, and post it if I have success.

Half an hour later - found it: link and discussion.
There's more going on here than I understand, so decide for yourself if it's useful.