Photography - Image Processing - Wide Angle Distortion
Correcting for Wide Angle Lens Distortion - Wide angle pictures often suffer from distortion. With a flat port in front of a wide angle lens you may get pincushion distortion and with a dome port in front of a wide angle lens you may get barrel distortion. And the wider the angle of coverage the greater the potential for distortion.
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.
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.
|Before and After Pictures
Click on image for larger image.
Click here for complete gallery of examples.
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.
Note 1: The pictures above 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 coefficients for this lens setup on a C-5050, using the Correct Option for the red, green, and blue channels, are a=0.00, b= -0.05, c= -0.15, and d= +1.20.
Note 2: The coefficients in Note 1 will work for all shots taken with this camera configuration with the exception that changing the amount of zoom requires a change in the coefficients.
Note 3: Correction for wide angle distortion should be done as the first step in editing i.e. before rotating or cropping the image.
Note 4: Paint Shop Pro 8.0 users have a built in option that seems to work as good as PanoTools. The option is located under Effects | Lens Correction | Barrel Distortion Correction and Fisheye Distortion Correction. The Fisheye Distortion Correction, using the default settings, does a good job of correcting for my setup with the INON wide angle lens and dome.
Note 5: Just because you can correct for distortion doesn't mean you have to or even should. In some cases, particularly with marine life and people, I like the fisheye effect because it makes the subjects appear closer.
New Photographers Please Note: All pictures shown have been edited. 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 don't either. For samples of before and after pics click