Understanding the Camera Crop Factor and How To Apply It

Note:  This is a rather long and technical article.  If you want to skip all the technical stuff, jump down to the “Summing Up” and “Action Plan” sections at the end to get a concise summary of the results and how to put them to use.

Recently, I was shopping for a new camera.  I was considering both DLSR and Superzoom cameras.

Zoom was very important to me as I one of my main purposes for getting a new camera was to photograph wildlife.  My current cameras have only limited zoom and I am constantly frustrated because I can’t get close enough to the wildlife to get a good shot.

But when I started comparing cameras, I immediately got confused.

DSLRs designate their lenses in mm focal length.  For example, 18mm, 140mm, 200mm, 300mm, etc.

Superzoom cameras, on the other hand, designate their lenses by zoom factor, which can range anywhere from about 35x to up to 83x on the new Nikon Coolpix P900 camera.  These factors are based on the zoom from the lowest focal length of the camera to the longest focal length and can be quite misleading.  For example, a 30x zoom on one camera can be quite different than a 30x on another camera, depending on the actual focal lengths used on each camera.

And these zoom values tell you almost nothing about how much objects will be magnified over what you see with your naked eye.  I have a 4x zoom compact camera that magnifies only slightly over what I see with my naked eye.  How disappointing is that?

As a result, these different designations make it extremely difficult to compare the different types of cameras and lenses.

What I really want to know is how much larger will a lens make an object appear over what I can see with my naked eye.  That’s all.

Well, it took a long time, but I think I finally have it all sorted out.

Let’s see what all it all means.