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

Camera settings for book scanning

Everything camera related. Includes triggers, batteries, power supplies, flatbeds and sheet-feeding scanners, too.
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dastor
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Camera settings for book scanning

Post by dastor » 12 Oct 2015, 08:59

I am a new user in this forum.
I'm trying to setup a system to scan old books for archiving.
My first problem is in taking a photo that is a 1:1 scan of the book page, like a real scanner.
I mean that a 20x30 mm page scanned at 300 dpi should be printed as a photocopy, without changing zoom or margins, etc.
At the moment I'm try different distances and apertures to find the right values

Thank you
Claudio

duerig
Posts: 360
Joined: 01 Jun 2014, 17:04
Number of books owned: 1000
Country: United States of America

Re: Camera settings for book scanning

Post by duerig » 12 Oct 2015, 09:33

There is not really such a thing as taking a 1:1 scan of a book. Any scanner you use, even the old flatbed scanners take scans of a particular pixel density (DPI). And each printer has a different pixel density it prints at (also DPI). So unless you have a printer already with a known DPI and that happens to equal your scan DPI, then any printer is going to scale the scan as it prints.

A better way to think of this is that scans with a higher DPI are usually better than ones with a lower DPI. The DPI is determined by the sensor on your camera and the zoom level/distance. So if you have a camera that takes 6000x4000 photographs and you perfectly zoom in on a page that is 10" high, you will get a 600 DPI scan. So look up the specs for your camera and try to calculate what DPI you can reasonably get. 300 is pretty good. Above 400, you start hitting diminishing returns.

FYI, the aperture size shouldn't make a difference here. The aperture size determines how much light hits the sensor and how much depth the in-focus area has. If you have an adjustable aperture, you want to set it to a moderate f-stop (around 8) and then make sure your lighting is bright enough and your shutter speed is slow enough that plenty of light gets to the camera. This will help ensure that the whole page is always in focus.

-D

dastor
Posts: 2
Joined: 12 Oct 2015, 04:40
E-book readers owned: kindle
Number of books owned: 500
Country: italy

Re: Camera settings for book scanning

Post by dastor » 12 Oct 2015, 12:39

Thank you,
so, if I have well understood, if I acquire a page at 300dpi, and then I print that file on a printer set at 300dpi, I should have a print that's the same size as the original?

Yes, you're right, the aperture size isn't related to the resolution issues.

Instead, let's say that I have a 35-105 lens, what's the best setting? Perhaps 50mm?

Thanks
Claudio

duerig
Posts: 360
Joined: 01 Jun 2014, 17:04
Number of books owned: 1000
Country: United States of America

Re: Camera settings for book scanning

Post by duerig » 12 Oct 2015, 12:45

If you have a zoom lens, my understanding is that the lens will be least likely to have distortions towards the middle of its zoom range. Other than that, it comes down to how high of a DPI you want to eke out. For most applications, it is easiest/best to zoom in just enough so that the camera captures the whole platen. And then once you have everything perfect don't touch it again.

-D

cday
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Re: Camera settings for book scanning

Post by cday » 12 Oct 2015, 13:56

dastor wrote:...if I have well understood, if I acquire a page at 300dpi, and then I print that file on a printer set at 300dpi, I should have a print that's the same size as the original?
Yes, in principle that should be the case...

But in reality, the camera will normally capture more than the page in at least one dimension, as the ratio of height to width of the page ('aspect ratio') and camera image will normally be different, so it will usually be necessary to crop the resulting image in one or both dimensions to obtain an A4-sized image. Capturing a slightly larger area in both dimensions and then cropping slightly will also likely result in a slightly higher quality image, as any distortions towards the edge of the lens will be reduced.

Another consideration is that it is unlikely to be possible to set up the camera for exactly 300dpi, so depending on what you aim to achieve that should be borne in mind. On the other hand, image editing software can be easily used to change the DPI value of an image, and hence its print size. Remember also that printers normally have an option to scale an image to fit the printer paper size, if that would help achieve the result you need.

qv_
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Re: Camera settings for book scanning

Post by qv_ » 02 Sep 2017, 07:01

dastor wrote:
12 Oct 2015, 12:39
Yes, you're right, the aperture size isn't related to the resolution issues.
This is not correct.
Aperature is related to the sharpnes of the picture and therefore also to the max possiibole resolution.
Every lens have a sweet spoot were is it best. arround f5,6 - f8 is normal.
And the cammera should be on ISO 100

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