DavidP #28649
Forum Pro
I'd trust Check Westfall over EXIF data.
http://www.robgalbraith.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=18&t=001350
Chuck: "As long as you are using an auto exposure mode like Program, it should be made clear that the actual exposure is controlled far more precisely than the numeric reading in the viewfinder display can indicate. At best, the viewfinder's display of shutter speeds and apertures is in 1/3 step increments, whereas the actual exposures (in AE modes) are controlled in 1/8 step increments. For this reason, you are better off to shoot your tests at a fixed aperture and ISO setting, then analyze the resulting files with Photoshop's Info palette set to a Grayscale (K) value to see the actual exposure difference in 1% increments."
WSLam: "That's what I thought. My Nikon's data would show the precise Shutter and Aperture that was used (in the EXIF). So there is no way I can find out the exact S and A the 1D uses?"
Chuck: "That's an entirely different question, but also basically irrelevant. As long as you can analyze the grayscale value of the images with Photoshop's Info palette, it's totally unnecessary to know the precise values calculated by the camera for shutter speed or aperture in an AE mode. As it stands, the values registered in the Exif data are rounded off to the nearest 1/3 or 1/2 stop according to the C.Fn 6 setting, when they are displayed in the Canon driver software."
DavidP: "Is this fact available in any documentation or on a Canon website somewhere?"
Chuck: "Probably not, but it's a fact nonetheless. I happen to be in a good position to know.
"
MichaelT: "In Av and Tv modes also, the camera will set exposure to nearest 1/8 step? Also...is this just for 1D or do any other EOS cameras set to 1/8 resolution?"
Chuck: "Yes. All of the EOS digitals and most of the EOS film-based cameras have this degree of exposure control, but I am not going to get into a discussion of which ones don't."
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise
http://www.robgalbraith.com/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=18&t=001350
Chuck: "As long as you are using an auto exposure mode like Program, it should be made clear that the actual exposure is controlled far more precisely than the numeric reading in the viewfinder display can indicate. At best, the viewfinder's display of shutter speeds and apertures is in 1/3 step increments, whereas the actual exposures (in AE modes) are controlled in 1/8 step increments. For this reason, you are better off to shoot your tests at a fixed aperture and ISO setting, then analyze the resulting files with Photoshop's Info palette set to a Grayscale (K) value to see the actual exposure difference in 1% increments."
WSLam: "That's what I thought. My Nikon's data would show the precise Shutter and Aperture that was used (in the EXIF). So there is no way I can find out the exact S and A the 1D uses?"
Chuck: "That's an entirely different question, but also basically irrelevant. As long as you can analyze the grayscale value of the images with Photoshop's Info palette, it's totally unnecessary to know the precise values calculated by the camera for shutter speed or aperture in an AE mode. As it stands, the values registered in the Exif data are rounded off to the nearest 1/3 or 1/2 stop according to the C.Fn 6 setting, when they are displayed in the Canon driver software."
DavidP: "Is this fact available in any documentation or on a Canon website somewhere?"
Chuck: "Probably not, but it's a fact nonetheless. I happen to be in a good position to know.
"MichaelT: "In Av and Tv modes also, the camera will set exposure to nearest 1/8 step? Also...is this just for 1D or do any other EOS cameras set to 1/8 resolution?"
Chuck: "Yes. All of the EOS digitals and most of the EOS film-based cameras have this degree of exposure control, but I am not going to get into a discussion of which ones don't."
--
The Unofficial Photographer of The Wilkinsons
http://thewilkinsons.crosswinds.net
Photography -- just another word for compromise