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New project to support avialogs.com and questions

Posted: 12 Feb 2013, 17:53
by avialogs
Hi,

I am starting the build of a book scanner to support Avialogs.com. We are raising funds on the site for it and so far so good.

Specifications are:
- A cradle to support documents up to 24" x 24"
- 2 Photographic reflex cameras with remote control. (Canon EOS rebel)
- Gorilla® Glass or normal glass ?

I have the following questions:
- All designs show a cradle with a 90 degrees angle. Some commercial solution are more flat. This 90 degrees is only to save place or there are other reasons ? I would like to use a cradle with an angle of 150 degrees as I will have to handle large and heavy manuals.
- Glasses : I plan to use gorilla glass for the glass part. Is there a real benefit versus usual glass ?
- Light : How much watt to use ?
- I want to use a reflex camera, what will be the best lenses to use ? (in term of focal, not optical quality)

I will start the build this week end and will post photos on this thread.

All suggestions, tips are welcome !

Benoit

Re: New project to support avialogs.com and questions

Posted: 14 Feb 2013, 11:18
by Shaknum
It becomes increasingly difficult to shoot the gutter of the book (the place where the pages meet the binding) if you have an angle greater than 90 degrees. I know this because I struggle with it on my custom scanner which is around 100 degrees. Less than 90 degrees can make things easier on the binding but cause problems with reflections (which are really always a problem). I think someone on the forums very recently was working on making the new standard scanner larger format, and Daniel has made some larger format rigs for Haiti, so you might want to check those out.

Re: New project to support avialogs.com and questions

Posted: 14 Feb 2013, 19:57
by Heelgrasper
Not all designs have a 90 degree cradle/platen. Right now I can't remember the exact angle on the hacker space model but I think it's 100 degrees or so. Daniel long time ago made a number of videos related to the subject: http://diybookscanner.org/forum/viewtop ... =17&t=1149. Short story about the 90 degrees is that it's very easy to work with when you're making a scanner and it works pretty good. The ideal angle is bit wider though.

With regards to lights the easy answer is: You need more than you think. But of course I don't know how much to you think you need. You ask about watts and that would differ depending on what type of lights you want to use. If I remember correctly the hacker space use a 10 watt LED floodlight but since you're building a scanner for large formats you would need more than that. For my single page scanner I use a 23 watt energy bulb and for some of the larger books I've scanned I wouldn't have liked using much less that that.

Regarding cameras, I guess when you say "in term of focal, not optical quality" you mean what focal length? That would depend on if your camera is full frame. In that case the classical focal length for minimal distortion would be 50 mm. If not it would be a bit less than that, perhaps 35 mm. But you will have to take into acount where you're going to place the cameras. It's no good if you can't capture the full page and not optimal if you capture lots of space around the page. There should be a number of Fields Of View (FOV) calculators online if you want to do some calculations rather than trial and error. And then of course you have to ensure that you don't get into conflict with the minimal focus distance of the lens.

Re: New project to support avialogs.com and questions

Posted: 16 Feb 2013, 13:03
by daniel_reetz
Benoit, can you please post some photos of the books you are planning to digitize? 24x24" is VERY large and poses some unique challenges. Also please check out Heelgrasper's link to my post about ideal platen angle!

Welcome to the forums, and thanks!