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

Cameras for the Hackerspace Scanner

Everything camera related. Includes triggers, batteries, power supplies, flatbeds and sheet-feeding scanners, too.
chrisgage
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Re: Cameras for the Hackerspace Scanner

Post by chrisgage » 03 Jun 2012, 04:02

In the case of the Sony W570 it's about 3 seconds in a static situation, but for some reason if your subject is moving that seems to increase. Fortunately the 570 isn't a candidate since it has no USB connection, but the A2200 was particularly cited as slow by CNET, excerpt below:

"Like most cameras in its price range, though, the A2200 is slow, so I wouldn't recommend it for regularly shooting active kids and pets. But that's my main reservation with it, so if all you need is a reliable automatic snapshot camera keep reading."

A scanner is nowhere near as active as kids or pets, but if the speed of the camera gets in the way when you are "on a roll" scanning pages, it could be disruptive...

tresho
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Re: Cameras for the Hackerspace Scanner

Post by tresho » 03 Jun 2012, 09:16

:arrow: I'm having trouble comparing the scanning of a book with taking a picture of a moving object. Scanning the pages of books while they are still moving past the camera seems beyond the scope of this group. When I am photographing pages in a bound volume (by flipping them with one hand and holding the camera with the other), it does take time for my hand to smooth out the page and get out of the way.
:arrow: How many pages per minute are you trying to capture?
:!: By the way, the results of my handheld "scanning" are not ideal, but are quite readable. OCR would probably have trouble with those images, but I am not doing that in this case.

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daniel_reetz
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Re: Cameras for the Hackerspace Scanner

Post by daniel_reetz » 03 Jun 2012, 12:17

A slow camera is a problem in general. The camera should fire when the shutter is pressed. I would like to hear from our A2200 owners if it is as slow as claimed. When I am scanning at a high rate of speed I can be flipping a page every second and a half or so.

Often with these compact cameras, if the flash is used it will take 3-7 seconds to recycle shot-to-shot. So any test that uses the flash is basically nonsense to us.

dtic
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Re: Cameras for the Hackerspace Scanner

Post by dtic » 03 Jun 2012, 14:13

I don't have an A2200 but I've used the A800 and find it fast enough. I can't imagine that the newer A2200 is slower.

If a camera feels slow then there are a few things to mitigate that.
1. Learn how long the camera delay between button press and start of the shot is. Many cameras have click sounds that gives you hint about such things. Once you know that you can press the button a little before the platen is pressed against the page and the camera will shoot the page right when the platen makes contact.
2. when using CHDK there are commands to lock focus on the camera. Not having to wait for the camera to autofocus for each shot saves some time. Do a test shot on any page in the book and then lock focus. Then shoot the entire book using that same focus. (This presupposes that the platen is fixed in the same position for each shot.)

tresho
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Re: Cameras for the Hackerspace Scanner

Post by tresho » 03 Jun 2012, 16:24

So any test that uses the flash is basically nonsense to us.
I would agree that it would be nonsense to use the on-camera flash when copying documents. An independent light source is necessary.

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Heelgrasper
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Re: Cameras for the Hackerspace Scanner

Post by Heelgrasper » 03 Jun 2012, 20:17

As I'm currently just using a very simple single camera scanner I don't have any troubles using my Canon PowerShot A810 but if at some point I was going to use it on a Hackerspace Scanner there's one thing that concerns me a little. It might not be a problem at all or there might be a very easy solution but it's a bit hard to tell without any hands-on knowledge.

If the 810 needs to focus and set exposure for every photo it's a bit slow. I can't give any test values for it but I did a test with focus lock and exposure lock and here I couldn't get it better than 2.5 secs per shot. And I think it's safe to assume that you can add at least 1 sec to that if the camera has to focus and evaluate exposure.

For this reason alone It would be natural to use the focus and exposure lock function. Other good reason would be to make sure that you don't get a few failed shots because the focus was wrong or the exposure was way off. In order to do that I need to push down the shutter button halfway so it sets the focus and exposure and holding the button in that position push two buttons on the back of the camera one at the time (the left and the right of the wheel thing most Canons have).

It seems to be a bit troublesome to raise the book to the platen, hold it there with one hand while pressing the braker down to the halfway point and then fiddle with the buttons on the back of both cameras. In particular since you might want to check the screen on the back of the camera to see if has focused on the book and set the exposure to something that seems right. Not to mention perhaps zoom a little.

Am I right about this being a bit troublesome or is there an easy solution (like a way to "lock" the book when raised to the platen)?
---
Jakob Øhlenschlæger
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fitterman

Re: Cameras for the Hackerspace Scanner

Post by fitterman » 06 Jun 2012, 07:02

I wonder if you can speed up some of these cameras by fiddling with the settings. Check that the AF Beam setting is OFF, that the AF Mode is not set to Face Detect and that the IS Mode is OFF. I don't have one of this model but I know on some of the Canon's I've owned, the auto-focus has really slowed down shooting.

I also see on pages 94-95 of the manual that the SD1100 has an auto-focus lock mode. The manual says to (1) turn on the LCD monitor, (2) center the subject (that'll be easy), (3) press the shutter half-way down and then press the macro/landscape button. Once in this mode the camera stays at a fixed focus mode for every shot until you press the macro/landscape button once more. I suspect if you do this you can speed things up significantly. Please let know your results if you can as I'm in the market for some cameras for my scanner.

markvdb
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Re: Cameras for the Hackerspace Scanner

Post by markvdb » 10 Jun 2012, 15:49

Hi all! I though you might like the bit of research I've been doing on cameras and speed. Some options:
* cheapest: direct import from China, refurbs, ... (you're on your own here)
* very cheap: Canon PowerShot a800: +-50€, slow digic 3 processor, 10 mpx, chdk beta
* cheap: Canon PowerShot a2200: +- 80€, faster digic 4 processor, 14 mpx, chdk beta
* quite expensive: Canon PowerShot sx40 hs: +- 350€ (or under $300 in the US), fastest digic5 processor, 12 mpx, actively developed chdk beta
* very expensive: Canon EOS 550D: >500€, digic4 processor, high quality components, 18 mpx, no chdk needed (remote capture, manual focus, ... present in stock firmware)
Mark
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daniel_reetz
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Re: Cameras for the Hackerspace Scanner

Post by daniel_reetz » 10 Jun 2012, 17:26

Thank you! I ordered an A2200. Seems like the current best option. I'll do some testing on it and report back.

markvdb
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Re: Cameras for the Hackerspace Scanner

Post by markvdb » 12 Jun 2012, 06:26

Just noticed the Canon PowerShot a2200 is getting end-of-lined. Most companies still have some stock, but that won't last another three months...
Mark
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