Fix misshapen images
Believe it or not, there are numbers of old (1830s and 1840s) certificates that are not fully rectangular. They are frequently skewed, meaning the sides are parallel and the tops and bottoms are parallel, but they are not quite at right angles. The shapes are hard to notice until one is straightening and trimming for display. I am left to wonder, "What's up with that?"
I don't have good explanations for those oddities. However, misshapen and distorted images of certificates seen on eBay are easier to explain. Collectors who use scanners will seldom encounter such problems, but they are the normal course of business when dealing with camera images.
Why fix at all?
Over the years, most images sent by contributors were scanned. These days, I am seeing an increased number of certificates photographed with smartphones plus some from digital cameras. Without special lenses and good lighting, it is not possible to get rectangular images of certificates straight out of cameras. Therefore, I fix a lot of distorted camera images so I can display certificates in the database.
Professional dealers all seem to use scanners, so eBay sellers are among a limited number of people who might need arcane knowledge of how to make photographic images of certificates sufficiently attractive for display in auction listings. Even then, one would need to balance the amount of time spent on repairs versus the potential additional profit that might be gained. For those people I have made a couple tutorials on fixing distorted images:
How much time to fix?
That all depends on how much practice someone has. The image above right is typical of many eBay images. This image would be easy to repair because the edges are almost straight. If I ignored the slight bend in the righthand edge, I could fix this in two to three minutes. The image would be back in rectangular shape although the proportions of height to width would be approximate. To achieve that would take another three or four minutes. If I were selling this certificate and didn't own a scanner, I would go with the 2-3 minute "good enough" image, especially considering the certificate's potential selling price.
But some certificates are more valuable AND more distorted
The image at right is equally typical of many eBay images, although perhaps a little better than some. The top and bottom edges are straight and that would be a definite plus. Removing the curve in the left side would take about a minute and the right side just a little longer. All in all, it should take only six or seven minutes to remove distortion in this photo. (Admittedly, there are radically different exposures between top, bottom, and sides and that is a separate challenge.)
The certificate shown was nice and flat, so that image would be dramatically easier to fix than images of certificates that had been folded. Distortions can be removed fairly well If sides have two curves (like gentle S-bends) or maybe even three. Throw a fold into the mix, and not only are we talking about a lot of time, but repair might not be worth the effort.
Is it easy to remove distortion?
Adding distortion is pathetically easy. Lots of photo editing software has features for distorting images in (supposedly) artsy ways. Twirls and swirls and inventive distortions are real nifty the first few times they're used. After a few minutes, though, ordinary mouse-drivers are left to wonder how they can put such effects to good use. Especially more than once.
It is a whole lot more difficult and takes special software to go the other direction and remove distortion. We know certificates are rectangular and that really helps in knowing where to start. Even after making certificates rectangular, there are challenges with adjusting brightness, contrast, colors, and smoothing out inevitable differences. There are helpful video tutorials on the web that approach the subject, although none involve fixing images like ours. If wanting to get good at removing photographic distortion, I advise acquiring software with those capabilities. And if doing so, I strongly, strongly, strongly suggest downloading and using trial versions and doing real-world repairs before buying.