Paradox
02-10-2008, 10:30 AM
I'm curious - how do the auto modes on DSLR's work out which values to adjust to correct the exposure? I've got a few ideas/theories - Do any of you know which is correct, or if not, which do you reckon it is? Or something completely different? For these analogies, I am leaving ISO out of things, as that's not part of what I'm looking for in this. Also assumed it's in full auto, not one of the scene modes on DSLR's that have them.
1. Balanced - I'd imagine this is the more likely option. The camera's software/hardware attempt to keep both a reasonably wide aperture, and a reasonably fast shutter speed, to accommodate most styles of photography. Shutter speed is kept fast enough to avoid most motion blur/camera shake, and aperture is balanced to get a reasonable depth of field whilst allowing enough light in to keep the shutter speed up.
2. Evaluative - Or that's the best word I could think of anyway. The camera communicates with the lens, and uses the focal length to 'Guess' the most likely form of photography and adjust accordingly - For example if it detected a wideangle lens, it would assume that most uses would be for landscapes, and would as such close the aperture to get a nice big depth of field, and would assume a tripod or support would be used, allowing it to lengthen the shutter speed if required. Or if a telephoto lens was attached, it would try to keep the SS as high as possible to avoid camera shake. This one is very unlikely as I see it - But I'm curious. Would it be possible, and if so, what would you think of it? I'm not one to use auto modes myself...but with the increasing number of people using DSLR's just to get good photos without really experimenting with manual etc, would it be a good move?
Just a bit of food for thought I suppose.
1. Balanced - I'd imagine this is the more likely option. The camera's software/hardware attempt to keep both a reasonably wide aperture, and a reasonably fast shutter speed, to accommodate most styles of photography. Shutter speed is kept fast enough to avoid most motion blur/camera shake, and aperture is balanced to get a reasonable depth of field whilst allowing enough light in to keep the shutter speed up.
2. Evaluative - Or that's the best word I could think of anyway. The camera communicates with the lens, and uses the focal length to 'Guess' the most likely form of photography and adjust accordingly - For example if it detected a wideangle lens, it would assume that most uses would be for landscapes, and would as such close the aperture to get a nice big depth of field, and would assume a tripod or support would be used, allowing it to lengthen the shutter speed if required. Or if a telephoto lens was attached, it would try to keep the SS as high as possible to avoid camera shake. This one is very unlikely as I see it - But I'm curious. Would it be possible, and if so, what would you think of it? I'm not one to use auto modes myself...but with the increasing number of people using DSLR's just to get good photos without really experimenting with manual etc, would it be a good move?
Just a bit of food for thought I suppose.