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

Macro Focus Slider

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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daniel_reetz
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Re: Macro Focus Slider

Post by daniel_reetz » 05 Feb 2010, 11:43

Afish wrote:Search for "macro focus slider" on EBAY. Would these be useful as camera mounts? They are available in 2-way or 4-way adjustable versions. This would add about $60 to $100 to the finished product.
I am thinking it could be used for going from smaller to larger books and as making minor manual focus adjustments without touching the camera focus.
I'm attaching an image so others can easily see what you're talking about.
macro.JPG
macro.JPG (67.96 KiB) Viewed 2498 times
Here's my take. First, I think these would make great book scanner camera mounts. The left-right adjustment and relative precision would be useful, although honestly I imagine you'd only set that once- like on the A590is, the offset for each camera is something like 1.5" and I set that and left it in place.

The forward-back adjustment wouldn't be worth much, in my opinion, because you have zoom controls on the cameras. If you use compact cameras, the depth of focus is great enough that small movements provided by a mechanism like this are probably not as good as just refocusing.

One downside to a mechanism like this is that you still need something to tilt the cameras.

If I had money, and I was trying to build a kind of ultimately adjustable scanner, I would go for these. I think camera mounts are still an open problem -- we have lots of solutions but none are particularly elegant, mostly because there's no standard camera that we are all using.

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Re: Macro Focus Slider

Post by daniel_reetz » 05 Feb 2010, 11:49

Misty wrote:However, are there any big gotchas to be had with that?
Not that I know of.
Misty wrote: Edit: Actually, it looks like the G10 works just fine with a linear polarizer; I must have been misunderstanding things.
I don't think so -- it's weird, actually. They must be doing all the metering and focusing through the sensor and not with auxiliary phase contrast detectors or other tricks. Hmm. I'm starting to wonder if the circular polarizer thing is specific to digital SLRs. That wouldn't be the first time that I mistakenly assumed DSLR issues were DSC issues. I'll read up on it.
Misty wrote:That makes things easier. Would a system with linear polarizers on both lights and lens have significant advantages over a circular polarizer on the lens only?
The idea is that if the light is polarized on both, you have maximum control of your illumination, because only the polarized light can pass. I think it's total overkill in this case and wouldn't buy you nearly as much as just making sure that your camera is not being illuminated by the scanner's light source, as in the copystand thread.

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Re: Macro Focus Slider

Post by Misty » 05 Feb 2010, 12:09

Those macro focus sliders look handy. I'm going to have to keep that in mind. Thanks for finding this!

Checking the Wikipedia page on autofocus, it looks like there's two kinds of TTL autofocus. The kind you're thinking of uses a beam splitter to direct light to an autofocus sensor and perform phase detection; that relies on unpolarized light or circularly polarized light coming into the camera, and will fail to send linearly polarized light to the AF sensor. Cheaper AF sensors that do contrast measurement don't have the same problem, so they can get along just fine with linear polarizers. It sounds like this is primarily a DSLR thing, since it shows up in cameras that have reflex mirrors. I mistakenly conflated the two types, so when I saw "optical TTL autofocus" I thought my G10 would also lose AF with a linear polarizer.

And thanks, Dan. I'll probably go with solely a lens polarizer, in that case.
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Re: Macro Focus Slider

Post by Afish » 06 Feb 2010, 00:04

My earlier question: "The Atiz BookDrive DIY requires horizontal and vertical adjustment but the BookDrive Pro requires only diagonal adjustment. Can anyone explain how they are able to eliminate one plane of adjustment?"

I think the answer lies in the statement itself. The BookDrive DIY must be adjusted upward (vertical) then to the back (horizontal) because the stanchion is in a 90 degree plane to the book page. The BookDrive Pro must have a stanchion that is angled upward and slightly to the back. Hence the camera is moved in a diagonal movement upward and to the back.

Therefore only the 2 way macro focus slider is necessary if mounted at a fixed angle allowing this diagonal movement. Then mount the ball head mount to the macro focus slider and the camera onto the ball head mount for the tilt adjustment. Instead of having the stanchion at an angle you can have the macro focus slider at the angle. [When I write "to the back" meant movement towards the top of the page].

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Re: Macro Focus Slider

Post by daniel_reetz » 11 Feb 2010, 23:21


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