Tendency for 650d to use too slow an ISO

First post for me, so hello everyone!

I spent the weekend taking photos of the kids on the new 650d. I've noticed an annoying tendency when shooting with auto ISO for the camera to choose a slower ISO than i might personally choose, and then also use a corresponding slower shutter speed to compensate.

So in partial shade, where I might manually choose a 200 iso and a shutter speed of say 1/60, the camera is going for a 100 iso with a shutter speed of 1/30. When shooting moving subjects such as kids, this is causing me grief with the focus.

I appreciate that i can manually select the ISO etc etc, but i wondered if anyone had experienced similar issues when going fully automatic, and what the camera is trying to achieve that i might be missing..?

Cheers.

Does it ever select high ISOs? I think I'm right in saying you can tell the camera the maximum ISO value you're willing to accept in auto mode in the menus somewhere... have you set that to ISO100 by any chance?

If you want to use the auto ISO function still then the best thing to do in that situation is slap the camera into Tv mode and ensure the shutter speed is high enough to freeze the motion... so set the shutter to 1/200 for example and let the camera do the rest!

The camera is trying to optimize image quality, which usually implies going low on the ISO. It doesn't know that you are trying to shoot running kids.

But that's why you have a DSLR, not a simple point 'n shoot. Set your camera appropriately, and it will perform for the task you have at hand with no problems.

Besides, the long exposure isn't giving you a problem with focus, but with motion blur. Two different things.

Sorry, yes indeed i meant motion blur. Thats also a good point on the Max ISO speed. I will check through the menus.

Im working my way up the features of the camera. I was an SLR user for years, but have only just ventured into the DSLR world. Been trying to see how well the camera functions when left to its own choices. I was at Disneyland and the photo opportunities were coming quick and fast, so often there wasnt the time to go as manual as i would have liked. In the end i just used the P program and manually set the ISO depending on whether i was inside or outside. I was also quite interested in how good the imaging was without using the flash. Using the kit lens at the moment (which is better than i expected) but feel that i will have to upgrade that pretty soon.

If you set it to sport, to let it know you are shooting moving subjects, it will choose a higher ISO/SS. The camera isn't AI, it doesn't know what you're trying to do.

Minimum setting for max ISO speed on the model you have I think is ISO 400, so it shouldn't limit you to 100 or 200.

The 1D-series allow more freedom here, but that's not what you have, obviously.

Yes, the advantage to rebel series cameras for beginners (or starting overers like yourself) is those simple scene modes right there on the top dial. Dial in the sports mode and you will get faster shutter speeds and usually higher ISO to compensate. Choose portrait and you get large apertures for shallower depth of field, and landscape mode uses smaller apertures. The camera prioritizes those settings and adjusts the other factors to compensate.

Not long after buying my rebel I learnt to lock the iso and shoot in av/tv modes then use exposure comp +/- as needed.

Sirrith wrote in post #14958759
If you set it to sport, to let it know you are shooting moving subjects, it will choose a higher ISO/SS. The camera isn't AI, it doesn't know what you're trying to do.

Sports mode also turns on tracking AF and continuous shot, so that would be the thing to do.

Auto mode is just for general photography and the standard rule for shutter speed of non-moving subjects is 1/focal length. If you were at the wider end of the zoom, it would assume 1/30 is enough, pick the lowest ISO that allows that and take the shot.

So I agree, I'd choose sports mode (running man icon) to start out with, but as you use your camera more, maybe try Tv mode at 1/400 shutter speed for kids.

Sounds like you're not actually trying to control the ISO, but the shutter speed. Your camera has a Tv mode for that.

TheBB wrote in post #14961347
Sounds like you're not actually trying to control the ISO, but the shutter speed. Your camera has a Tv mode for that.

+1 It sounds like the OP may may be shooting in Av or perhaps even one of the auto modes. Also wonder why he doesn't set the ISO himself instead of leaving it up to the camera.