Good point. This very large book will lay flat a whole lot easier than a lot of the books I'm trying to scan, and it wouldn't be that hard to get a plate of glass or acrylic to lay flat on each page; then it'd just be finding an angle to avoid glare. But there's a lot of things I want to scan for my personal use that are approximately A4 size, so they're not paperback books. I can't think of much that I would scan along the lines of paperback books. There are a few public domain books that were rebound as hardbacks by a library (and DEFINITELY need the platen help just to keep it open - an overhead scanner would never work with those!), and those are on the smaller side, but most books I'd be scanning are closer to the size of an 8½"x11" piece of paper or larger.dpc wrote: ↑23 Mar 2021, 18:56Rather than build a scanner large enough to handle that one large book, you might consider scanning that one book manually one page at a time with a single camera on something like a crude copy stand and a build your scanner based on the size of the majority of the books you have to scan.
The reason I say this is because the geometry of the scanner will need to change beyond just the platen/cradle size to handle larger page sizes. The light source will need to be raised to avoid reflections that will be visible on the platen surface and the farther the light is away from the page the less light will illuminate the page surface (you can lower the light for books with smaller pages though, provided your light position is adjustable). Your camera position will also need to be adjusted between scanning books with the large and small page sizes (for example, if you simply set the camera position to frame the largest books you'll ever scan, you will be throwing away image resolution when scanning smaller sized books). A physically smaller scanner is also almost always easier to operate and takes up less storage space. I would imagine that you won't want to try to scan a stack of paperback books with something the size of an Archivist.
Good to note. Thanks for the info.dpc wrote: ↑23 Mar 2021, 18:56The reason for choosing a platen angle of 100 deg. over 90 deg. is to prevent a reflection of the adjacent platen pane into the camera's view. Daniel has a good video demonstrating the problem on this website somewhere (see links below) that I'd encourage you to watch. Building a platen with a 100 deg. angle is more complicated than the simple 90 deg platen, but if you're using acrylic where you can drill mounting holes through the platen you can use common 'L' brackets that have been opened up slightly from 90 degrees. If you're using glass panes for your platen you'll probably want to use grooved end plates, with the grooves being 100 deg apart. You can cut the grooves with a table saw or a router. Or you could simply attach some aluminum angle to the sides of the end plates to hold the glass against the lower edge of the end plate (the Archivist scanner uses this method).
The downsides of acrylic is that it does scratch and it attracts dust particles more easily than glass (triboelectric effect). The upsides though are that it's cheap, easy to work with (cut/drill), and crystal clear.
He does mention that, but in the instructable he lists the three ways he came up with for setting up the platen, and that was the second try. His third (and final) suggestion was a "screw together approach".cday wrote: ↑24 Mar 2021, 03:29In his video David Landin describes a method of fusing two pieces of acrylic to make the platen, if that works easily as described it should be simpler than drilling holes and using brackets. If the platen does over time scratch it could also easily be replaced. If brackets are used, it would be as well to search online for advice on drilling acrylic to avoid the risk of cracks, but maybe Doranwen's brother already knows that. Either way, it might be wise to buy more acrylic than is required initially unless it is readily available when needed.
See Step 11 here: https://www.instructables.com/Book-Scan ... ages-an-h/
He's got pics of the different ways to attempt that. So I'm thinking taking the L brackets and bending them slightly wider than 90° might be the easiest?
My brother isn't concerned about that part. When I asked him what he thought about the angle, he said: "Making the platen at more than 90° is doable, but it's going to make the trig on the cradle pieces quite a bit more complicated. The brackets that support them come easily at 90°, but I don't know if they come at 100°, and if not, we'd have to place them at just the right places."