----- Original Message ----- From: P�l Jensen Subject: Re: DOF in DSLRs - HELP ME PLEASE...
> > Depth of field is a factor of reproduction ratio and aperture. > > Focal length doesn't enter into the equation. > > > No. DOF has everything to do with focal lenght. Reproduction ration doesn't eneter the picture even if the DOF scale on your lenses are decided with reproduction ratio in mind. DOF is the relationship between whats in the plane of focus and whats outside it. This ratio won't change regardless of how much you magnify an image. Sharpnes does change with magnification. Eg. a lens has a certain sharpness regardless of how much you blow up the image; same with DOF at a certain focusing distance, subject magnification (on film), and aperture. I mean, talking reproduction ratio into DOF definition is like taking reproduction ration into lens sharpness definition. By that definition my Limited lenses sucks because my 8X10 meter images aren't sharp! Reproduction ratio is how large the subject is on the film, not the print. If you keep the subject the same size on the film, then the DOF will remain constant at any given aperture and focal length. This is not format dependent. It is just aperture and subject size (reproduction ratio) dependent. William Robb
