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

^ or V platen?

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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Misty
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Re: ^ or V platen?

Post by Misty » 18 Dec 2009, 15:30

Yes, but they don't always do a good job of it. That's why it's important to make sure you have a good exposure before you commit to it with a long series of shots.
The opinions expressed in this post are my own and do not necessarily represent those of the Canadian Museum for Human Rights.

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daniel_reetz
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Re: ^ or V platen?

Post by daniel_reetz » 18 Dec 2009, 16:27

DrAltaica wrote:
Misty wrote:Exposure is still relevant to digital cameras. You're not exposing film, but you are exposing the CCD/CMOS to light; proper exposure is when the right amount of light is being let in to ensure a properly bright image.
My point is that the camera can adjest the Exposure itself. It's a little thing called 'auto exposure'
Umm, as Misty said, the camera can adjust the exposure itself, but you don't necessarily want it to. For example, if you have a page with a dark picture on it, it will expose differently than other pages, and that will look bad. Auto-exposure is designed for outdoor scenes, not books. The assumptions that go into auto-exposure algorithms aren't necessarily compatible with book scanning.

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Re: ^ or V platen?

Post by DrAltaica » 18 Dec 2009, 18:44

daniel_reetz wrote:For example, if you have a page with a dark picture on it, it will expose differently than other pages, and that will look bad.
Never had any problem it before scanning two books with a camera. I tried to get my Sanyo S770 to mess up with some pages with dark picture.
Any more suggestions for this mystery condition that would cause auto exposure to fail?

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Re: ^ or V platen?

Post by spamsickle » 19 Dec 2009, 00:42

It's not a mystery condition, it's the way auto exposure works. If you're happy with the pictures you get with auto exposure, then you're happy. I wasn't happy, and agree with Misty and Dan that it's a mistake to depend on it. If you are going to use auto exposure, you probably need to add a stop if you want your white pages to be more white than gray, and if you do that your dark images are going to be more gray than black.

Since film cameras also offer auto exposure, whether your camera is film or digital is irrelevant as far as exposure options. We're all using digital cameras, since no one wants to shoot, develop, and scan ten rolls of film for a 350-page book.

Still, you're free to do things your own way, if you're satisfied with the results. In general, I don't think most people will want to depend on auto exposure or auto focus for a book scanner.

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Re: ^ or V platen?

Post by Antoha-spb » 21 Dec 2009, 02:43

I would agree that auto exposure is not the best thing for scanning. Apart from what others said about lightness, there is a depth-of-filed issue, depending on aperture used (this is still relevant to the digital photography, just in case... :-) ). If the distance between the platen and the camera is more or less close to the diagonal dimension of the platen, photos taken with the diafragm wide open will look blurry at the edges. To avoid that one may set the camera to the Aperture Priority mode or use the manual settings. The latter is more convenient as you don't need to guess about shutter speed, i.e. how fast you can turn the pages.

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Re: ^ or V platen?

Post by wels » 27 Dec 2009, 21:32

when imaging books, you probably want to exploit that specific situtation to gain optimal results: for example the lighting setup, it is constant for the whole document. auto-exposure will just (possibly) add uncontroled non-constness: different white-black levels for each image/page - bad for further processing, ocr ...

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