Zoom-factor? Think again.

I learned something interesting the other day, that I guess I already knew. As a photography equipment salesman, it makes life a bit tougher, but as a photographer it makes perfect sense.

When shopping for a digital camera back in 2003, the salesmen I talked to were touting the APS-C sensor on my Canon EOS 10D, saying that it has a "1.6x magnification factor" and that it will make my 100mm lens into a 160mm lens. I said "Wow, that sounds great!" I was interested in shooting sports at that time, and with that, the longer the lens the better.

With this "zoom factor," the new portrait lens would be a 50mm rather than the 80mm needed for film portraits (because 50 x 1.6 = 80). Since the APS-C cameras hit the market, the lens manufacturers have had no problem selling their cheap 50 mm lenses.

I went to some training last week hosted by a Nikon training rep. He made a very good point regarding this issue. The APS-C is not a "zoomed" sensor. It is a CROPPED sensor. Let's say you have two cameras: one full-frame sensor and one with APS-C sensor. The sensor in itself does not magnify the image. It simply crops the image to a smaller size (about 37.5% smaller). When you take that image that is cropped and print it on the same size print, it appears that the lens was zoomed in. This is why people are under the impression that a lens will act like a longer lens on the cropped sensor cameras.

The fact is that a 50 mm lens is a 50 mm lens, no matter what camera or sensor in front of which you attach it. A 50mm lens is not a portrait lens. It does not "act like" an 80 mm lens. The compression and distortion will be identical when using that lens on a full frame sensor as on an APS sensor.

Now I am rubbed the wrong way every time I hear the term "35mm" equivalent. All the "digital lens" manufacturers have started printing the lens' "35mm equivalent" on the packaging. The truth is that the lens is what it is. There is no equivalent. No zoom. Just cropping.

Let me hear your thoughts.