Daniel Reetz, the founder of the DIY Book Scanner community, has recently started making videos of prototyping and shop tips. If you are tinkering with a book scanner (or any other project) in your home shop, these tips will come in handy. https://www.youtube.com/channel/UCn0gq8 ... g_8K1nfInQ

Most effective ways to reduce glare and unwanted reflection.

Built a scanner? Started to build a scanner? Record your progress here. Doesn't need to be a whole scanner - triggers and other parts are fine. Commercial scanners are fine too.
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SemisolidSnake
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Most effective ways to reduce glare and unwanted reflection.

Post by SemisolidSnake » 24 Aug 2013, 01:47

So, I built the hackerspace scanner from Daniel's kit, and it has been sitting in my apartment for a while. I'm using two A2200s with CHDK and a remote electric trigger.

I ran one book through it as a test and noticed glare on every page, presumably the reflection of the actual wood of the scanner. This was not too big a deal for Scan Tailor, since this is a completely black and white book. However, when I start scanning color books, I don't want that glare or reflection or whatever it is. Could we please assess my situation and see what the best course of action would be?

1) This is probably really dumb on my part, but I did not paint the wood black ahead of time. I was eager to get working on it when it arrived, so I jumped right in. I figured the black was cosmetic. Plus, I built this in my apartment, so painting would have been much more difficult to sort out. So, it's fully assembled in its nice natural wood color right now. Let me empathize this: I AM NOT GOING TO TAKE THIS THING BACK APART. Daniel, your design is awesome, but it was a pain in the butt to put together, what with all the sanding to make the mortise joints fit. I also had to install a couple of extra L-brackets to hold the cradle in place, if you must know. Mechanically, it works beautifully, but it'd be too much of a pain to disassemble unless absolutely necessary.

So, my main question is how important is it for this thing to be black in terms of reducing glare and reflection? Does the black actually absorb all those stray unwanted photons? If it is important, do you think I can get away with taking an army of Sharpies to it? I've tried that on some scrap and it looks like a black stain, where you can still see a little sheen from denser wood grain. I want to make this as simple and unmessy as possible even if it is somewhat time consuming. If I do need to color the equipment black, do I need to do the whole thing or just the cradle and areas seen by the camera? I just want to make a decision here.

2) How important is it to have a light blocking cover over the whole apparatus. When I did my test run, I did it by a window, so definitely plenty of outside light. I could probably build a PVC frame and drape black fabric over it. If so, what would be the best light blocking fabric for the job? Could I forgo the fabric draping if I just did my scanning in a completely dark closet?

Is there anything else I need to be aware of when reducing glare? Are there any settings on my cameras that can help. I assembled the scanner over several months with what tools I had available, and I just learned how to use Scan Tailor about a month ago. I'm eager to get this thing in ideal working order, so I can start scanning the legions of technical books I have.

Thanks for the advice, guys.

vitorio
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Re: Most effective ways to reduce glare and unwanted reflect

Post by vitorio » 25 Aug 2013, 05:27

I spent several hours studying the glare on my scanner, same build and cameras, and my results are:
  • Turn the lights off. My scanner is under a scaffolding, so the rest of the area's lights don't affect it, but the lights directly by it all need to be turned off. The LED lamp should be the only light. (If you cannot have the room's lights off, you should seriously consider a blackout tent that covers the entire scanner and you.)
  • Paint the interior top half black. From my other post: "You know the platen assembly? Front plate, back plate, and everything in between and up? You know where that sits on the cradle assembly? That spot? Okay, so, if the lights are off, it seems like the only parts of the scanner that need to be painted black and covered to protect from glare, is everything from that spot on up."
  • Cover the top half of the scanner. I have black blackout cloth (blackout cloth stuck to black cotton) hanging down around the entire platen assembly. I open it up to futz with the cameras, but when I'm scanning, it's all down in place and the lights are off.
  • Don't scan anything larger than an 8.5x11 page on each side. Anything larger than that and you'll get the reflection of the LED lamp.
Once I set all this up, I white-balanced to white paper and I haven't needed to adjust it since.

I have not upgraded to thicker glass, or to polarized/museum glass yet.

Hope this helps.

SemisolidSnake
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Re: Most effective ways to reduce glare and unwanted reflect

Post by SemisolidSnake » 27 Aug 2013, 00:00

vitorio wrote:I spent several hours studying the glare on my scanner, same build and cameras, and my results are:
  • Turn the lights off. My scanner is under a scaffolding, so the rest of the area's lights don't affect it, but the lights directly by it all need to be turned off. The LED lamp should be the only light. (If you cannot have the room's lights off, you should seriously consider a blackout tent that covers the entire scanner and you.)
  • Paint the interior top half black. From my other post: "You know the platen assembly? Front plate, back plate, and everything in between and up? You know where that sits on the cradle assembly? That spot? Okay, so, if the lights are off, it seems like the only parts of the scanner that need to be painted black and covered to protect from glare, is everything from that spot on up."
  • Cover the top half of the scanner. I have black blackout cloth (blackout cloth stuck to black cotton) hanging down around the entire platen assembly. I open it up to futz with the cameras, but when I'm scanning, it's all down in place and the lights are off.
  • Don't scan anything larger than an 8.5x11 page on each side. Anything larger than that and you'll get the reflection of the LED lamp.
Once I set all this up, I white-balanced to white paper and I haven't needed to adjust it since.

I have not upgraded to thicker glass, or to polarized/museum glass yet.

Hope this helps.

Yeah, this helps give me a lot of perspective. I'll do this in a darkened room, and I'll build myself a little light-blocking drapery. I found some black denim at Wal Mart last night (the only WM I know that still sells fabric), and it blocked all light as far as I could tell. Failing that, one of the light blocking window shades they sell would also do the trick.

I think I am going to try to my Sharpie method on the top half of the scanner. It's time consuming, but more accurate and less messy while the thing is still assembled. If it doesn't work, I can always just paint over it.

Scanning 8.5x11 is about the limit of the hackerspace scanner anyways, but some of my textbooks are so large that they might push that limit.

The only thing I'm confused about is your mention of white balancing. I'm a total photo-editing noob, so I'd appreciate additional clarification.

Also, are there any specific settings you use on your camera to get better results? I basically just turned off the flash, zoomed in and let the camera do the rest of the work. Seemed to work pretty well, but if there are any tweaks, I'd certainly love to know about them. Thanks for your help.

vitorio
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Re: Most effective ways to reduce glare and unwanted reflect

Post by vitorio » 27 Aug 2013, 00:34

SemisolidSnake wrote:The only thing I'm confused about is your mention of white balancing. I'm a total photo-editing noob, so I'd appreciate additional clarification.

Also, are there any specific settings you use on your camera to get better results? I basically just turned off the flash, zoomed in and let the camera do the rest of the work. Seemed to work pretty well, but if there are any tweaks, I'd certainly love to know about them.
Depending on your goals, you'll probably get fine enough results that way, but I'm interested in recording the book as close to accurate as I can manage. That means if it's an older, yellowing book, I don't want the camera to try and adjust the yellowing page to white; I want it to record it as it actually is, and if I want it white, I'll process it later.

My understanding (from reading the forums) is that you want to have the camera do as little work as possible, with a fixed focus, so you get exactly the same DPI and exactly the same picture, shot after shot. On my previous camera, I had it set at "1.9x zoom, Program Auto, 4:3 16M shots, 0 EV, ISO 80, white balance auto set against a white piece of paper in the platen, multi AF focus, multi metering mode, normal smile sensitivity, face detection off, and DRO off." My Canons (same as yours) are set similarly: I'll zoom in three times, and "set in Program mode, ISO 80, white balanced against a sheet of white paper pressed against the glass platen with the scanner lamp on and overhead lights off and blackout cloths in place, center brightness, no flash, 'Fine' quality."

The while balance means, I'll put two blank white pieces of paper on the cradle, centered to take up the zoomed-in camera view just like a book would, pull the cradle up to the platen, and then set a Custom white balance against that paper. These instructions look about right: http://www.manualslib.com/manual/275697 ... ml?page=86

And then I leave it alone.

What this means is that the camera knows that color means "white" and everything else is based on that. Everything will be color-accurate. Yellowed book pages will look yellowed.

Finally, my understanding is that you can't do a fixed focus with the stock Canon firmware (the camera will autofocus every time you take a shot), but you can do it with a custom script via CHDK. A fixed focus is important because it's possible for the camera to have trouble autofocusing (say, on pages with no text and only faint details). A fixed or manual focus is set once (with a page right up against the platen) and then left there. You'll get the exact same focus and exact same DPI every shot.

dpc
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Re: Most effective ways to reduce glare and unwanted reflect

Post by dpc » 27 Aug 2013, 12:07

I think I am going to try to my Sharpie method on the top half of the scanner. It's time consuming, but more accurate and less messy while the thing is still assembled. If it doesn't work, I can always just paint over it.
Wow, you must have a lot of free time on your hands. I'd just buy a pint of flat black paint and get a rag or small sponge and dip it and apply it by hand like you would with a wood stain. Wear some latex gloves though.

The easy way to determine the source of glare/reflection is to put a piece of solid black paper under the platen instead of a book. This will work more like a mirror and you can see what contributes to the glare quite easily.

If you begin to see a reflection of the overhead LED light in your images when scanning larger page sizes, you may have to raise the light and/or move the camera farther away from the platen and zoom in (reducing the camera's field of view).

Finally, my understanding is that you can't do a fixed focus with the stock Canon firmware (the camera will autofocus every time you take a shot), but you can do it with a custom script via CHDK.
My Canon point and shoot A495 cameras have a manual focus lock using the out of the box firmware. There are posts here in these forums where people mention this feature with other Canon models so you might want to verify. Perhaps Canon dropped that ability in the newer models?

vitorio
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Re: Most effective ways to reduce glare and unwanted reflect

Post by vitorio » 27 Aug 2013, 13:01

dpc wrote:My Canon point and shoot A495 cameras have a manual focus lock using the out of the box firmware
Ahh, it's called an "auto focus lock" on this one, assuming this online manual is correct: http://www.manualslib.com/manual/275697 ... ml?page=96

I wonder if it stays preserved across camera restarts. Zoom doesn't, for example, but you can script that with CHDK.

Thanks for the correction.

spamsickle
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Re: Most effective ways to reduce glare and unwanted reflect

Post by spamsickle » 27 Aug 2013, 15:33

For the past couple of years, I've eliminated glare and reflection by eliminating the pane of glass between page and camera. I hold the pages flat with the tips of my fingers on the lower margin. I don't have to raise and lower a platen each time I turn a page.

This method doesn't usually make the pages as flat as a platen would, but the results have been acceptable to me.

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