Correcting for Wide Angle Lens Distortion - Wide angle pictures suffer from distortion. With a flat port you get pincushion distortion and with a dome port you may get barrel distortion. And the wider the angle of coverage the more distortion you get.
When shooting underwater, the effects of wide angle distortion are often not noticeable because, unlike buildings, there are few straight lines. After all, who knows how round a French Angelfish really is. But with wrecks and panoramic reef shots distortion becomes very noticeable.
Fortunately there is a software fix for this problem. It's called PanoTools. PanoTools plugins are available for Adobe PS, Adobe Elements, and Paint Shop Pro that run on Windows, Mac, and Linux platforms. And the plugins are free! You can obtain PanoTools at Helmut Dersch's website .
Installing and setting up PanoTools can be a bit of a hassle. However, once you have it running, it takes just two clicks of the mouse to transform a picture. For details on how to install and use PanoTools software, see Correcting for Lens Distortion and Chromatic Aberration using Software at Cameras Underwater's website.
Is this magic or what? The before and after pictures below illustrate the dramatic improvement that PanoTools makes to distorted images. The effect is most apparent in images that we think we know what the subject should look like e.g. straight lines on ship wrecks and peoples faces. By deduction the other pictures must also be more accurate e.g. reef panoramas, fish, and turtles. But to me they look just fine without correction for lens distortion.
Note 1: The pictures below were taken with an INON wide angle lens and an INON dome port with the zoom set to maximum wide angle --- about 127.9 degrees. The PanoTools Radial Shift settings for the after images, using the Correct Option for the red, green, and blue channels, were a=0.00, b= -0.05, c= -0.15, and d= +0.120.
Note 2: Correction for wide angle distortion should be done as the first step in editing i.e. before rotating or cropping the image.
To access large versions of the photos, see Peter's site here
New Photographers Please Note: All pictures shown have been edited with Paint Shop Pro 8.0. Typically I rotate, crop, resize, remove back scatter and other artifacts, adjust the histogram, remove color cast, adjust brightness and contrast, final adjust saturation, and sharpen. It takes me 5 to 10 minutes per picture to do these steps. My reason for mentioning this this is that your pictures, as taken, may not look as good as these and I want you to know that mine aren't either. For samples of before and after pics click here .