Hi i'm new here. I have a question about exposure and the confusing world of flash photography.

It's said that to expose the ambient light correctly, you need to adjust the shutter speed, and to expose for the amount of light from the flash you need to adjust the aperture. If that's how it is, ok, fine. But doesn't that limit our creative possibilities? If you're hand-holding your camera, and you find that the ambient light demands a low shutter speed of, say, 1/20 sec, unless you widen the aperture to allow for a higher speed - so you're already losing creative control of the DOF by doing that.

I'll leave it that for the mo - don't want to overcomplicate things, which i'm probably already doing. Except to say that, iTTL seems a lot more straight forward because you can use the speed you want, aperture, and iso for the ambient light and the camera just adjusts the flash as appropriate. And you use exposure compensation to adjust the flash power, as required.

Thanks

I am about to start playing with focus stacking for macro photography, but I have a question. There are two techniques that I know of. The first technique is simply to change the focus gradually, picture by picture. The second technique is to use a focusing rail and, rather than changing the focus, moving the camera forward gradually, shot by shot to get the photos for stacking. Here's my question; Using a focusing rail is supposed to eliminate the potential movement of the lens that you could get each time you try to manually adjust the focus for each shot. But doesn't the use of a focusing rail change, even slightly, the position of the lens to the subject each time you adjust it? Does that negate the advantage it supposedly has? Stacking in postprocessing stitches the pictures together to try to eliminate the effects of any movement of the camera from picture to picture, so is there a benefit from the use of a focusing rail?

A favorite selling point on new cameras is how high the ISO number will go. A higher ISO number makes the camera more sensitive to light, which means higher shutter speeds and smaller apertures, right? In the the next breath the "experts" are telling us to use the lowest ISO possible, to reduce "noise". I understand that, ideally, a fine camera should have high ISO settings with a minimum of noise. But why an ISO number in the tens of thousands when most photographs are taken in the hundreds?