Here's another tip. If you need to scan a picture that is bigger than your scanner can handle and you need to do two scans, then stitch them together, here's a tip that will save you time.
The scanner's light bulb doesn't have the same uniform brightness across it. That means that one side of the bulb will be brighter than the other side. If you were to simply scan one part of the picture, then slide the picture over to scan the rest of it, the two halves of the picture won't match up in brightness when you try to stitch it together.
Let's say that you want to scan a centerfold from a magazine. The centerfold is the center page of the magazine, so it is one long piece of paper. Let's call one edge of the centerfold side A, the middle where the fold is, we'll call side B, and the other edge of the centerfold we'll call side C.
Okay, place the paper on the scanner so that you will be scanning one edge (side A) and the middle (side B). Let's say that side A is on the left side of the scanner's glass, and side B is on the right side of the scanner's glass.
Once you've scanned this half of the centerfold, rotate the page 180 degrees so that it is upside down. Now, you place edge C of the centerfold on the left side of the scanner, and that leaves side B (the middle of the centerfold) on the right side of the scanner....the same side it was on in the first scan.
Once you've made the scan, you will rotate the second scan 180 degrees so that it is properly oriented with the first scan. When you put the two scans together to stitch them, the middle sections (side B) will have the same brightness and you won't need to make any adjustments to the brightness to get them to match up.
If you don't rotate the centerfold, what happens is that edge A of the centerfold is placed on the left side of the scanner and side B (the middle) is placed against the right side of the scanner. If the light bulb in the scanner is brighter on one side....say the right side....then the scan will have side B (the middle) brighter than the left side. When you make the second scan, if you just slid the picture over so that side B (the middle) was on the left side of the scanner, and edge C was on the right side of the scanner, what you'd get would be that side B (the middle) is now on the darker side of the light bulb.
When you went to try and stitch the two halves together, you'd be placing the first scan, which had the brighter side of the light bulb on the B side, against the second scan, which had the darker side of the light bulb against the B side. The end result would be two mismatched brightness levels. Rotating the picture 180 degrees for the second scan would eliminate that.
