This tutorial will be updated some time after the winner of the Mascot Competition (
[link] ) is announced.
A simple tutorial to explain how to clean up your pencil sketches and scanned images in Photoshop, and add a bit of colour to them to ready them for uploading!
Tutorials are done in Photoshop since many programs will have similar features, in similar places.

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A temporary fix would be to try drawing on A5 paper, or don't fill up the A4 page, so that you avoid the areas where the scanner has issues. It's not ideal but it's a start...
But I would still like help with the above questions.
Your scanner is most likely A4, so that should be fine, but having the paper still on the sketchbook is likely the major problem.
The reason for the shadows is that to take a 'photo' of the paper, a scanner blasts light at the paper, and records what light bounces back, but in areas where the paper is not flat on the scanner some light escapes so the scanner sees those areas as being darker.
So that's the key: paper is completely flat on the scanner.
If your scanner has a lid, you usually use that to make sure the paper is flat, but obviously you can't if you've got a book.
For storing everything that has been scanned. I also have one for storing all the pictures I want to redraw and then scan. Then you're archiving them, rather than throwing them away
(Also, sorry for replying so late!)