Scanning Stamp Collections, what DPI to use (and what background color to use).
The program does a decent job of automatically extracting postcard images, but stamps need a bit more care. First of all you need to let RansenScan know that you are looking for small images, you do this by simply setting the minimum image size:
Also I'd suggest that you use 600 DPI (but see here) and that if your scanner has a light background lay a piece of black A4 card over your stamps to enhance the contrast.
For example here...
...you can see that RansenScan has managed to extract only 7 of the stamps on the scanner platen (see the column of 7 stamp images on right of the screenshot above). You can easily add the missing stamps manually and adjust their orientation, but it would be better if the program could extract more images automatically.
The idea came to me that a black background might help, a piece of card which completely covers the scanner bed, and which rests on the backs of the stamps. Here are the results:
with a black background the scanner has extracted 13 of the stamps. It is important that the black card covers all of the scanner bed.
The thumbnails on the right side seem a bit small, but that is partially because I've reduced the size of the screen shot in order to create this web page. And with RansenScan all you have to do is double click on the thumbnail for final corrections:
The grid is there to help you align the stamp horizontally, just click on the Fine Angle Movement buttons to rotate the stamp by small amounts.
You can increase or decrease the size by using the Fine Sizing buttons, and/or simply crop the image to the extents you want. After fiddling about a bit I got this (I switched off the grid in this example):
Oddly enough to get the image (within the stamp) aligned properly I had to have the whole stamp very slightly angled.
Another thing RansenScan can do is color correction, though you probably do not want to move the sliders too much. Here is another before and after shot, before:
And here is a screen shot after I've increased the contrast and saturation by 30% each (see the 1.30 in the Saturation slider and Contrast slider):
It does improve the look of the stamp, but you have to be careful not to go much beyond 30% else you are really risking changing the characteristics of the image.
If there are stamps in your scan which have not been picked up automatically you can add them simply by selecting them with the mouse and clicking on the "Add Sub Image Icon" in the toolbar:
Once you have your individual stamp images you can save them quickly by clicking the "Save All Sub Images" item under the File menu.The tutorial teaches you this and other time saving tricks.
RansenScan is a Windows (XP, 7, Vista, etc.) program and has a free demo available by clicking on then button below.
Actually it depends on what use you want to make of the scanned images. If you want to print them at four times (or more) of the original size, then yes, 600 DPI is an appropriate choice. If you simply want to sell them on ebay or keep an image for your records or maybe show them on FaceBook then 300 DPI is adequate. Have a look at these images (especially at the nose profile and the 7p text):
There really is very little difference between 300 and 600 DPI at these display sizes. Just as important is the format. Use JPG if you want small image size, use PNG if you want to preserve detail.