Using a fisheye for wide-angle coverage on a DSLR

Most digital SLRs (DSLR) have an image sensor that is smaller than a 35mm negative. As a result the field of view of the captured image is smaller when compared with the same lens on a 35mm SLR. This discrepancy in lens coverage is commonly referred to as a "cropping factor" in DSLRs and becomes a hinderance when searching for an affordable lens to give a wide field of view. One way to obtain wide-angle coverage on a budget is to use a fisheye lens.

Since a fisheye lens has its heaviest distortion near the edges of the frame, most of the effect is lost when used with a DSLR. In fact, if the scene has very few straight lines it can be hard to tell a non-rectilinear lens was used (see the photo at right for an example).

In some cases it's desirable to have a wide field of view without any noticeable distortion - this is where software correction is helpful. Luckily there is a free software solution, PanoTools that can take care of this problem (and many others). PanoTools is extremely powerful. Unfortunately it is fairly cryptic to use. The simplest configuration and the one covered in this writeup is to use the program as a PhotoShop plug-in (This of course requires Adobe PhotoShop).

Note: The values below assume a 16mm fisheye lens on a 1.6x crop factor DSLR.

1. After installing the plug-in you should see a Panorama Tools option in the Filters menu, which contains several tools. Select the Adjust tool.
2. On the Create Panorama dialog select options as follows:

   

3. Click Set and enter the following values:

   

4. Click Ok.