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

How to alternate between 2 tethered cameras with triggers

Everything camera related. Includes triggers, batteries, power supplies, flatbeds and sheet-feeding scanners, too.
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pashamkhan

How to alternate between 2 tethered cameras with triggers

Post by pashamkhan » 25 Feb 2012, 11:40

Hello! I'm a completely new member hoping to put together his first DIY book scanner. For now I want to stick to this basic setup, but with some important enhancements having to do with the cameras and software.

These are the modifications I want to make:

- Two tripod-mounted cameras instead of one (and two lamps, of course) -- I haven't yet bought the cameras and could use some suggestions.
- The cameras should be operated by remote shutter release (I believe this is what it is called), i.e., pedals. I assume I'll have to have one for each camera.
- The cameras should be tethered to my computer so that I can see what is on the viewfinder screen on my computer monitor.
- The tethering should also allow the shots to be saved quasi-instantaneously to my computer, preferably as jpegs with sequentially-numbered filenames.
- I want to have _both_ cameras tethered to the computer. This is the really tricky part, as far as I can see, since I don't know how to tether two cameras, and besides this I would want the software to alternate between the two cameras. Assuming a left-to-right book (actually, most of the books I'd want to scan are right-to-left), what would ideally happen is this:

1. The righthand camera is active. I press the trigger, and the image of lefthand page #1 is saved as 1.jpg. _Automatically_ the software switches to the lefthand camera.
2. The lefthand camera is active. I press the trigger, and the image of righthand page #2 is saved as 2.jpg. Automatically, the software switches back to the righthand camera.
3. Flip the page, replace the platen, and repeat above sequence to the end of the book.
4. Postprocessing.

Given all of the above, here are my questions for you folks:

1. What pair of cameras (optimal quality but moderate cost) should I buy? They must support tethering either with native or third-party software.
2. Is it possible to tether _two_ cameras to one computer at the same time, or to have the software automatically alternate input between the righthand and lefthand cameras after each shot?
3. If #2 is possible, is it feasible to have the software name the image files in sequence in spite of the input alternation? This would be nice as it would eliminate some postprocessing, but of course it isn't essential.

Thanks!

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Drake Ravensmith
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Re: How to alternate between 2 tethered cameras with trigger

Post by Drake Ravensmith » 26 Feb 2012, 09:19

I don't know anything at all about tethering cameras. Nothing. What I have read on the subject on this forum would suggest that what you want isn't possible. I don't think anyone has gotten two cameras tethered to a computer as camera tethering is somewhat difficult to begin with. But I don't know for sure. I can tell you that having two cameras triggering one at a time with separate triggers is a waste of time. Most of us here trigger both cameras at the same time. Renaming the files after the fact only takes a few minutes with Infranview and is probably a better bet since sometimes the cameras fire out of sync or you get a blurry image or you fire accidentally and images have to be tossed.

You say you want to tether the cameras so you can see what's on the viewfinder on the screen. Most cameras have an av out which would allow you to accomplish the same thing with some old tvs. I'm going to recommend that you read my instructional. Even if your scanner is going in a completely opposite direction, it has a lot of information and ideas you may find useful.

http://diybookscanner.org/forum/viewtop ... sion+cable

pashamkhan

Re: How to alternate between 2 tethered cameras with trigger

Post by pashamkhan » 26 Feb 2012, 11:44

Thanks, Drake, that's quite helpful. I suppose that as long as I get the initial shot right, I don't necessarily need tethering at all. It'll just take a bigger investment in terms of postprocessing with Irfanview. But from your documentation, I understand that some cameras can be directly attached to monitors(?) That would be neat.

I've noticed that many of the scanners on this site have two cameras with only one trigger, but I'm not 100% clear on how to make this work. I see your neat SDM/CHDK USB remote switch solution, but I want to keep my hands free and use a switch that I can step on. Any ideas with regard to this? Thanks again.

Pasha

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Gerard
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Re: How to alternate between 2 tethered cameras with trigger

Post by Gerard » 26 Feb 2012, 14:53

there is no ready to use solution for now,
chdk cams are avaibale from 50€ to >200€ even the cheapest >8MP canon cam is suitable for book scaning

i can tell you somethink to the chdk soultion, the chdk community is currently working on liveview, in my opinion there will be no read to install solution in this year, but if you a developer you can have it now, just look in the chdk forums for the threads

a simpler solution is:
buy some cheap car lcd screen or usb video capture sticks and use the video out of the cameras, or just attach a mirror to the camer screen

for tethering you can choose a camera that is able to "remote capture" with ptp, gphoto should have no problems to work with 2 cams

if you go for the chdk solution, have a look chdkcam or ptpcamgui or ptpcam

but why do you need some separate triggers?

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Drake Ravensmith
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Re: How to alternate between 2 tethered cameras with trigger

Post by Drake Ravensmith » 26 Feb 2012, 17:44

Go to page two of my build thread. There is a photo showing how I placed my camera trigger on the floor so I can hit it with my foot.

Most canon cameras can be connected directly to tvs. Many of the newer, 12 or higher megapixels cameras do have one limitations. They don't have a separate port for that. Before you buy, download the manual and check which av cable the camera uses. The avc-dc300 has a stereo plug and means the camera has separate ports. The avc-dc400 has a mini usb port and means that it does not which means you can't use an electronic trigger and have preview monitors.

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