Peter's Answer: Yes, cropping an image made by a camera with the 24x36mm sensor can provide the same effect as the field of view crop produced by cameras with a smaller sensor. After you finish cropping, less of the scene is included in the photo, so the primary subject does appear larger. But by extensively cropping a photo, you will be discarding millions of pixels, so the image will be smaller: with less resolution (or fewer megapixels). This concept applies to any full-frame camera of course, whether it provides 12, 21, 24 or 36 megapixel resolution.
The more you crop an image the smaller it will be (with less resolution). Of course, this is less of a problem with your 21.1 megapixel camera than it would be with the 12 megapixel EOS 5D (or for a Nikon owner, with the 12 MP D700). If you do not plan to make a print larger than 13x19-inches, even a 10 megapixel image (roughly 30 MB is size) of high quality should allow you to get excellent results. And in my experience, that is the largest that most photo enthusiasts make or order.
Learn more about photography...Peter Burian teaches three interactive online online courses at BetterPhoto's school of digital photography:
-Mastering the Digital Camera and Photography
-Boot Camp for New Digital SLR Owners
-Mastering the Canon EOS Digital Rebels
In addition, Peter's photography appears in two how-to books co-authored by Jim Miotke and Kerry Drager: The BetterPhoto Guide to Creative Digital Photography and The BetterPhoto Guide to Photographing Light.
Article by Peter K. Burian. To learn more about photography, explore the many online photography and Photoshop classes offered here at BetterPhoto.com.