Some people eat, sleep and chew gum, I do genealogy and write...
Saturday, December 11, 2010
Stitching photos for preservation of large documents
Some documents are too large to fit comfortably on a scanner. Others are so large or perhaps inaccessible, such as large paintings or charts, that they cannot be easily fitted into one photograph, even with a wide angle lens. Here is an example of a photo taken with a wide angle lens in separate photos and then stitched together into one seamless photograph:
You can click on the image to get an enlarged view. There is really no limit to the number of photos that can be stitched or the resolution that can be obtained.
For genealogists faced with oversized documents, stitching presents one inexpensive solution to obtaining a high quality print or digital file. There are a few rules.
1. Make sure your camera is a perpendicular to the item being photographed as possible. Sometimes the document is not flat and my may have to work hard to get an image that is all in focus. Try taking the photos in a strong light with no flash.
2. Only use a flash as a last resort. A flash, especially one mounted on the camera, has a tendency to create hot spots on the image. These defects obscure the detail in the final image. If you are trying to take a photo in a repository, even if they allow digital photography, which isn't always the case, it is almost certain they will ban flash photography. If that is the case, you can try to use the largest aperture lens on your camera and try to hold the camera steady. If the repository discourages flash photos, they will probably also discourage tripods, but you can always ask. All they can say is no.
3. The closer you get to the photo, the narrower the lens angle should be. For example, if you have a very wide setting on your camera or a wide angle lens you should take the photo from a location so that the item to be photographed fills the narrowest lens you can use and still get the photo. Lenses with designations of 35mm or less, i.e. 28mm, 24mm etc., are considered wide angle lenses. Ultra-wide angle lenses are those with really low numbers like 17mm, 16mm, 8mm etc. Even though it would seem to be better to use a wider angle setting or lens, the results are counter-intuitive. The wide angle lens will result in a greater or lesser degree of distortion. Most point-and-shoot cameras have some built-in zoom capabilities. It is a good idea to experiment with your camera at different zoom levels or with different lenses until you are satisfied with the results.
Ok, so here is an example of a composite or stitched photo. First I have loaded a couple of the pieces. These are photos that were taken with a relatively standard lens at a comfortable distance that gave a lot of good detail.
If you look closely, you will see books that I was using to try and keep the document flat since it had been rolled since it was first received. I took the various parts to get a very much higher resolution final document. So, here is the final stitched document:
The final document was stitched and the book-weights removed in Photoshop. The file is about 11.8 megabytes. You can click on all of the images to get a larger view. There is some distortion of the final picture because of the curvature of the original, but all in all it is a pretty good photo. You may also notice that each of the individual photos (there were a lot more) was a slightly different tone or color. This seems to be normal but not too difficult to correct with Photoshop.
Let me know if you would like a more detailed explanation of the process.