This and That: Curing Lens Distortion
       By Elizabeth B. Wright  September 2006

First, the good news. The camera which quit working on our vacation last month was still in warranty (just barely) and Sony repaired it at no cost and it has been returned to me in working order. I was out the postage to send it to Sony, but I didn’t mind that since I now have a working camera back.

On to more about the replacement camera I bought to use during the rest of our vacation.

Many of you will remember the recent past when serious photographers tested their film camera lenses for flaws. There were all kinds of tests for “vignetting”, “distortion”, etc. The photo magazines were full of articles on the subject along with suggestions for what to do if bad problems were encountered. I shudder to think of what those solutions involved using darkroom techniques. But now we have: (drumroll) “Digital Cameras”.

Last month I talked about buying a replacement digital camera for the one which quit working suddenly while we were on vacation. The original camera was a mid-range priced camera, not cheap but also not out of the ballpark. It took great pictures and had a lot of good features. The second camera was too expensive for what it is, but again, not unaffordable as long as I didn’t buy anything else while on vacation. I had a similar one at home which I have used on occasion and should have had with me as a backup. Lesson learned.

So why am I rehashing old news? The explanation is that SONY, in my estimation, really goofed with the Cybershot DSC-S600. While still touting their line of Carl Zeiss, Vario-Tessar lenses, the lens itself had a terrible barrel* type distortion. I discovered this when I downloaded my pictures at home and found pictures I had taken of a doorway looking like something seen in a funhouse mirror. My immediate reaction was that SONY had accidentally put a defective lens in the camera. I now have a replacement DSC-S600 instrument, and it has the exact same distortion as the first one. I feel my money has been poorly spent, but that might be another story for later.

What to do with the pictures. Ah, that was a challenge. The doorway pictures were obvious, so it was back to finding an imaging program which could easily make the necessary corrections. JASC PaintShop Pro9 turned out to be quite adequate for the repairs. Below you will see the original picture and the one using the effect tools in PSP9 and the final cropped image. As usual, there was some trial and error to get the right combination of effects, but eventually I got something that resembled the actual door.

      1. After starting JASC PSP9 and using the browser, open the picture to be adjusted. The first step for my picture was to rotate the it 90º as I had originally turned the camera to take a vertical view of the doorway. Once this was done the following steps are as follows:
      2. Click “Effects” on the menu bar, then click “distortion effects / lens distortion”. This will open the dialog box where you enter values to change the picture.
     3. Since my picture demonstrated a “Barrel”* type distortion, I needed to use the option that would reverse this phenomenon.
Under “Settings”, I chose “pincushion” from the drop down menu (accessed by the small downward arrow at the right edge of the “Distortion type” choice line) for the effect I wanted to create.
After trial and error for this particular picture, I chose the values under “Center offset” of:
Vertical 0, Horizontal 25 and in the “Strength” box I input a value of 15. I chose “Color” for the “Edge mode”.
      4. When the program made the calculations and came up with the altered picture, I then had to crop out the black spaces created by the pincushion effect. Obviously you will lose some of your picture when cropped, so if there is any element you want to keep, you might choose to live with the black pinched edges. The pictures below will show the results of these actions.

*Digital Photography Review website at: dpreview.com/learn/?/key=barrel+distortion
“Barrel Distortion By Vincent Bockaert” “Barrel distortion is a lens effect which causes images to be spherised or "inflated". Barrel distortion is associated with wide angle lenses and typically occurs at the wide end of a zoom lens. The use of converters often amplifies the effect. It is most visible in images with perfectly straight lines, especially when they are close to the edge of the image frame. See also the opposite effect, pincushion distortion.”

Elizabeth Wright is a member of the CCOKC and secretary to the Board. She is a regular writer for the eMonitor