I've got some new sketchbook pages up and this time around I've run out of scans. So, twenty pages of scanning later I decided I might as well share my drudgery with the internet. Fellow artists might appreciate knowing how this sort of thing is done.
Step 1. Preventing Bleed-Through
What's bleed-through? You know how when you put a page of artwork onto a light table the intense light turns it see-through like tracing paper? Well the same thing happens when you scan an image. If there's art on the other side of the page, or even the page behind that you're going to have it bleed-through into the image you want. Here's an example:
In this case, our image actually has art both from the reverse page and the page behind it bleeding though. It's kind of a mess. The solution is to stick a sheet of black construction paper behind the image you're trying to scan. This will absorb any excess light instead of reflecting back into the image you want. However, if you're drawing one-sided on loose sheets of paper it's actually better to stick white inserts behind it so that your artwork stays bright.
Step 2. Scanning the Images
I scan my sketchbook pages at 24-bit colour and 600 dpi. I don't fret over my other scanner settings or lining up the page because I tend to do that stuff later in Photoshop.
Here are the three scans that make up a typical two-page spread. I do it like this because the seam tends to warp and shade anything close to it. Scanning the middle separately tends to give better results. It also means I don't have to fuss over fitting the entire page into the narrow window my scanner bed can see like when I'm scanning individual pages. Afterwards the pages are reassembled in software.
Step 3. Merging The Scans
To put the scans back together, open Adobe Bridge. Select the images you want to reassemble and go to Tools > Photoshop > Photomerge.
The options Photomerge gives you are mostly irrelevant. They're designed for photo-stitching panoramic photos so they actually correspond to different geometric projections of 3D scenes. I use the Collage option to prevent any geometric distortion of what should be flat images. You can try the others though, in this case they give comparable results.
When Photomerge is done it spits an image out into Photoshop. Whatever seam there might be from joining the three images is completely invisible, at least to my eyes. These are the images I tend to save out as the master scans I work from.
Next time I'll be explaining how I clean-up my sketchbook scans in Photoshop and get them ready for the web.