ISO settings on the 40D

Until recently I've been using a Canon S3is, then a few days ago I bought a 40D. Until today I mostly haven't been getting the kind of results I want because of the apparent effect of the ISO settings on the 40D. With the S3, I would shoot with ISO 80 if it was bright sunshine, 100 most of the rest of the time, 200 for twilight shots, and occasionally 400 for night shots. So straight away I set my 40D to ISO 100. The result was much slower shutter speeds than I would have expected.

When I tried ISO 400 on the 40D, I seemed to get better results. Given how good the 40D is for high signal-to-noise ratios, I could have just left it on 400 most of the time, but I want to understand the difference between ISO settings on the S3 and on the 40D, and how to get better control over the 40D. So, for the time being, I've set the ISO to Auto and I'm going to watch which setting the 40D selects for which kinds of shots. For the type of photography I do, I tend to shoot long and wide: mostly using my 70-300mm IS USM lens at the long end, with the camera in Av mode so I can control DOF.

Can anyone who's used an S3 (or any similar bridge camera) and a 40D shed a little light?

I don't remember problems moving from the S3 to the 30D a couple of years ago. Maybe if you posted a pic with ISO 100 on a sunny day it would help us to help you.

If you can, make sure the exif info is attached to the shot, or if not, include it with your post.

Hope we can help you -- on sunny days you should have a lot of latitude with ISO 100. Sometimes the camera can get tripped up if you are exposing for a dark area, though. If the camera meters a shadowy area it will set the exposure to turn it "medium grey", which will slow down the shutter speed in Av mode and will cause highlights to be overexposed.

There are a few practical approaches to getting a balanced exposure which involve metering a portion of your image and then adjusting your exposure according to how that portion compares to medium grey. For instance, if you meter a blue sky, dail in +1 in exposure compensation, lock that exposure, then take your pic, you should come out reasonably balanced (check the histogram for needed adjustment).

Congrats on your 40D! Have fun!

What apertures are you actually shooting at?

The shutter speeds each camera uses for an identical exposure will be the same if you also have selected the same ISO and aperture. I have a feeling you are using smaller apertures on the 40D at the same ISO which is giving you slower shutter speeds.

Read some basic photography primers so that you understand how ISO, aperture and shutter speed work and then try the cameras head to head. It should make sense.

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JeffreyG wrote in post #5254290
What apertures are you actually shooting at?

The shutter speeds each camera uses for an identical exposure will be the same if you also have selected the same ISO and aperture. I have a feeling you are using smaller apertures on the 40D at the same ISO which is giving you slower shutter speeds.

Read some basic photography primers so that you understand how ISO, aperture and shutter speed work and then try the cameras head to head. It should make sense.

I know about the relationship between ISO, aperture and shutter speed. But your question above about what aperture I'm shooting at gave me the clue I need. I'd forgotten that the S3 goes down to f/2.7. I was used to shooting wide open on the S3 without thinking about the numbers. Of course, the 70-300mm lens I'm using only goes down to f/4. So of course the shutter speeds are going to be slower. D'oh!

Sorry about the mix-up, folks. Put it down to a senior moment.