Try to get the biggest exposure you can,
OK, not sure I’ve ever heard that expression. Please explain?
Ok - exposure measures the amount of light per unit area that the sensor (or film) collects. It is measured, properly, in lux seconds. The more lux seconds the bigger the exposure. In practice, it simply means get as much light into the image that you can. For a fixed scene brightness, that means as long a shutter speed and as large an aperture as you can. Shutter speed is likely to be limited by reducing or eliminating motion blur. The aperture will be limited either by your DOF requirement, the maximum aperture of the lens, or a desire to use the lens at its 'best' aperture. So far as noise goes, you always want the most light in the image, how important to you in relation to camera shake or lens resolution or DOF only you can judge.
Where you might want to set a limit is the other end (not sure Canon auto ISO will do this) where you'd want it to reduce shutter speed if the exposure got too much at 100 ISO, to avoid blown highlights.
Bob
Again, please have patience here with a newbie, can you expand on that?
A digital sensor just count photons, so whatever exposure it has it will count them, and you can process the output to get the range of output tones that you want. The exception is when it reaches its maximum count at base ISO. If the light levels in the image are higher than that, you will lose the highlights in the image irrecoverably. So, if you hit that problem, it is the one case that you need to reduce exposure, either by closing down the aperture or reducing the shutter speed (usually the latter, since it leaves the picture looking the same, assuming it was short enough to freeze motion blur in the first place)
Using a 70-200 f4 w/IS.
Here are some shots from last Saturday on my practice walk around Asheville where I live. Used AV for the first time, I’ve been shooting Manual since I started and will return to it for NY.
http://www.flickr.com/photos/retsurfer/sets/72157626729792564/
I wish I had your eye for the grab shot - some nice pictures there. Now, the problem you have with using auto ISO is that Canon just doesn't get it. As I said, what you'd like to be able to do is set the slowest shutter speed and largest aperture you can, and just have the camera set the ISO for you, except when you hit base ISO, when you want the camera to reduce exposure via the shutter speed and/or aperture. Unfortunately, you can't set Canon's auto ISO up like that (you can, I understand, with Nikon, although it's not exactly intuitive, it means the right combination of auto ISO limits and auto exposure mode).
So, back to your specific case. I can't see with this kind of work and a lens as good as yours, any reason to use anything other than f/4. The exposure time assuming IS gives 2 stops, could be 1/60 to cover all focal lengths on the zoom (if you were really cute, you'd want to change shutter speed as you zoom). Now as a rough estimate using the 'sunny 16' rule, in most normal daylight illumination, you will risk blowing the highlights at 100 ISO, so in that situation, you'd want to reduce the shutter speed.
The best compromise might be to stick to Av, f/4 at 100ISO, as soon as you see the shutter speed drop below 1/60 swap to M, f/4, 1/60, auto ISO. If the ISO goes back down to 100, swap to Av again. On my canons, as I remember, M mode retains settings between uses, so you can set the f/4, 1/60 in advance, and just change mode. You have to go into a menu to select auto ISO, though.
Canon manages to catch you allways. Another way of working would be Av, with the rear wheel assigned to ISO - then when the shutter speed goes down to your limit, you just boost the ISO to keep it there. So far as I know, youi can't do that, either.
Maybe someone with more familiarity with the 60D's auto ISO can suggest something better, or even more helpfully, point out that I'm wrong about the 60D's limitations..
--
Bob
