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.
Afish
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Macro Focus Slider

Post by Afish » 03 Feb 2010, 19:50

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.

DDavid

Re: Macro Focus Slider

Post by DDavid » 03 Feb 2010, 20:45

I just ran across these today myself. They would be nice but if I understand it
right the 2 way is only in and out adjustment and the 4 way adds left right and a
ball head is needed for tilt. Tilt would be far more useful I think as I intend to set
the focus manually with a ruler and set the focus to the center of the depth of field.
The tilt in and out and tilt left to right is of far more concern to me to keep the corners
in focus than the movements the 4 way provides. But the 4 way would still be nice and I
may spring for it at some point.
I also ran across a few statements today that indicate that polarizing gel filters on both the
lights and standard polarizing filters on the lenses are best for controlling glare which
appears to be a better use for my money.
I have yet to finish a book scanner so take that with a grain of salt. I do have a degree
in photography and had a camera attached to my body during most of the 70's but have gotten
away from it. The head man at Minolta repair in Atlanta once asked how many wars my XK
had been thru when I sent in for service :D

Afish
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Re: Macro Focus Slider

Post by Afish » 03 Feb 2010, 21:16

DDavid,

Thanks for your input. Tilt can be added by attaching it to a "ball head camera mount"" an additional 12.99 each without shipping.

Not having a built scanner myself I am still fishing for ideas. It looks like many members are getting acceptable scans so I am not sure about the value of polarizing filters.
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?

The two way macro focus slider is much cheaper (29.90 each shipped) than the 4-way so this coupled with the ball head mount would still be a reasonable $100. It seems to have 4 inches of adjustment. Is this enough?

spamsickle
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Re: Macro Focus Slider

Post by spamsickle » 04 Feb 2010, 01:25

I bought polarizing filters for my cameras, but I'm not using them. The (expensive) reflection-suppressing glass I used in my platen seems to cut the reflections sufficiently. The only time I'm really aware of reflections is when I leave the Brodart covers on the books' jackets when I shoot them.

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Re: Macro Focus Slider

Post by Misty » 04 Feb 2010, 11:31

I can't comment on whether polarizing filters are needed with anti-reflective glass/acrylic, but this video shows that it seems to be very effective for seeing through glass. For the sake of paranoia, I might well go for both anti-reflective glass and a polarizing filter when I build.
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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Re: Macro Focus Slider

Post by daniel_reetz » 04 Feb 2010, 17:05

Remember that with a polarizer, you lose 50% of the light. So a polarizer on the light, minus the losses due to the inverse square law, minus the losses at the lens -- you'll need some serious illumination to overcome all those losses.

Also, traditional document photography relies on linear polarizers, not the circular polarizers that are designed to work with phase contrast AF systems in digital cameras.

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Re: Macro Focus Slider

Post by Misty » 04 Feb 2010, 17:15

The lighting is a good point - I'd be building for high illumination anyway, but I'd definitely want to take that into account.

My G10 has TTL AF, so that definitely does rule out linear polarizers. Why is linear usually preferred in document photography?
Last edited by Misty on 05 Feb 2010, 10:05, edited 1 time in total.
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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Re: Macro Focus Slider

Post by daniel_reetz » 04 Feb 2010, 18:43

I probably said that wrong.

Circular polarizers are expensive. If you're just filtering with a polarizer at the lens, that's alright. However, if you choose to polarize the light source and the lens, then you need the polarizers to be of the same type to avoid weird lobes or unevenness in the final image.

In the past, at least with large scale art/map photography, people used linear polarizers on light source and lens because they're cheapish and work fine with film. I don't think that there are light-source-sized circular polarizers commonly available, or at least, I've never seen 'em.

On the other hand, it's all a moot point if you find the right exposure and focus settings without the polarizer and then just manually program them into the camera.

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Re: Macro Focus Slider

Post by Misty » 05 Feb 2010, 10:25

That makes sense.

From what I've seen, people are typically getting quite acceptable results by polarizing the lens only - not the light source. However, are there any big gotchas to be had with that? If I use a circular polarizer on the lens only, then I can keep AF and don't need to worry about finding an optimal manual focus setting. It looks like I can get a reasonable price on a 72mm circular polarizer ($75) by buying from Lensmate who sell the best Canon G10 filter adapters.

Edit: Actually, it looks like the G10 works just fine with a linear polarizer; I must have been misunderstanding things. 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 opinions expressed in this post are my own and do not necessarily represent those of the Canadian Museum for Human Rights.

DDavid

Re: Macro Focus Slider

Post by DDavid » 05 Feb 2010, 11:36

Dan, Misty I wasn't seriously considering doing the lights except as a last
resort. It's more complicated than just putting a filter on the light from what
little I've found on it. It also involves reflecting the light at the right angle.
I've found polarized film fairly cheap but would be a problem with heat I
expect.
My linear polarizing filter from my film SLR's doesn't help a lot but there a quite
a bit stronger one's available but they get expensive according to the number
of coats.
Dan would it be possible to make a new thread and move these posts out
of this one? I didn't mean to hijack this thread. Sorry

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