Archived posting to the Leica Users Group, 2000/11/09
[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]>At 06:25 AM 11/9/00 -0800, you wrote: >>If you crop a picture shot with a wide angle lens and then enlarge it >>so it is comparable to a print made through a longer lens, the DOF >>will be the same in both prints. The actual lens doesn't affect DOF. > >um...not to be argumentative, but i disagree... >I am considering DOF to be the point of nearest acceptable focus to >the point of farthest acceptable focus in any given image. Like >Perspective, it is set on the negative as a latent image by your >choice of lens and aperture. Nothing you do to it during or after >development of the negative can change the DOF (or perspective such >as apparent background compression.) You can change Composition and >other characteristics (Gamma, RGB, hue, contrast, etc..) in the wet >or digital lab, but Depth of Field, Focus and Perspective are >determined in camera. > >Carpe Luminem, >Michael E. Berube (I presume we agree that sharpness is not equal throughout the range of distance which we call DOF, but drops constantly as we get further away (in both directions) from the point which is in perfect focus.) We certainly agree that the DOF covers a larger range behind and in front of the subject on which we focus if we use a 21 mm lens than if we use a 90 mm lens provided the camera to subject distance and the aperture are the same in both cases. However, if you want the subject to be the same size when you print your negatives, then you will have to enlarge your 21mm negative more than the 90 mm negative and those things just on the DOF limit of the 21 mm lens will then, on the print, have more or less the same sharpness as those same things will have on the print made from the 90 mm lens negative as the 90 mm negatiive require less enlargement. Of course, many other factor come into play, including the quality of your film and processing. I do not think perspective is set by your choice of lens and aperture. I think it is dependent on the relative distances between the subjects photographed and the camera. Look at the final prints of pictures made with different focal lengths, but make sure they show exactly the same things, no less no more. If the pictures you compare do not show exactly the same thing, then your are discussing cropping and picture content, not perspective. (I looke at wour werb site and conclude we also disagree on ties and bow ties ; -) - -- Christer Almqvist D-20255 Hamburg, Germany and/or F-50590 Regnéville-sur-Mer, France