Originally posted by Sean Nelson I think you're mistaken there. Cropping is exactly the same as using a longer focal length lens - if you crop the image so that the subject fills the frame it's going to have the same depth of field as if you had taken it with a focal length long enough to have the subject fill the frame (assuming the same f/number was used for both shots).
Have a look at my two macro pictures posted above. In the full-frame version the bee looks to be mostly in focus, but in the cropped view you can see that only part of it is.
Sorry, you misunderstand. The attached two shots, scanned from slides, illustrate. The first was taken with a 105 macro lens at a distance to fill the frame; the second was taken with the same lens at a distance away and the final shot cropped about 2/3rds to give an image size similar to the first shot. You will see that in the first image the antenae are out of focus whilst in the second they are sharp to the ends. Sorry about the quality of the slides, they are quite grainy from using 400 ISO film.
John