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Thread: DSLR Scanner: Camera Supports and Positioning

  1. #11
    joseph
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    Re: DSLR Scanner: Camera Supports and Positioning

    That looks good Rick-
    really like the handle for what I presume is the fine focus control-

    A couple of things-

    Regarding your light source-
    I read somewhere (I think I linked to it) that the light source should be daylight, since that is the native color balance setting for a DSLR, and that would give maximum DR.
    Since you're using a slide projector, you could easily mount up a full blue gel in a slide, and do a custom white balance-

    The other point is regarding film flatness-
    If I develop myself, I don't use clips, and the sheet is undistorted.

    However, films that have been developed on hangers are often distorted- by the clips, and the heat of the process, for colour films.
    I've been having trouble keeping those ones completely flat myself, within the tolerance of the depth of field, which, as you have said yourself, is minute-

    Looks like a very nicely engineered setup-

  2. #12
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    "No pessimist ever discovered the secret of the stars, or sailed to an uncharted land, or opened a new doorway for the human spirit." - Helen Keller
    www.peterdesmidt.com/blog

  3. #13
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    Re: DSLR Scanner: Camera Supports and Positioning

    Quote Originally Posted by Peter J. De Smidt View Post
    Peter, all three of the links are the same.

    That's actually a tolerable price. But the tricky bit is that the bed is opaque, requiring the light source to sit on top of it, or requiring one to mount the camera on the bed. I first looked at it and added up what I'd spent--whew! Still cheaper. But this one would be easier to automate than what I did.

    Rick "rendered still-stuck on this project by unexpected good weather--requiring extensive yard work" Denney

  4. #14
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    Oops. Sorry about that.
    http://gigamacro.com/
    http://www.smallworldexplorations.co...technology.php

    I agree. The hardest part would be the light source. In talking with John, currently there's 4" from the mdf platten to the bottom of the Z-axis, which could be increased a bit by using 1/4" aluminum instead of the mdf. He also would make a 6" (or possibly higher) z stage instead of the standard 4" for a bit extra. Unpainted version in the past have been $75 cheaper than painted, but I don't know if that's still an option. I wonder if the bed couldn't be made out of glass or acrylic, perhaps even with the lead screw off to the side. We might lose a little bit sturdiness, but we aren't pulling an end mill through material, and so I doubt it would be an issue. We could also probably get by with much smaller motors than the cnc people use. On the other hand, the other motors are tried-and-true, and if this scanning thing doesn't work out, or we get done scanning all of our stuff, we'd have a nice cnc unit, which could be really handy.

    What appeals to me about this design is that it should be very easy to automate, and it could be put together with very simple tools. To make my prototype, by contrast, one would really need a decent table saw and a drill press. In addition, making linear stages looks quite challenging. In particular, machining down the end of a lead screw (or ball screw) to fit a bearing probably requires a lathe, which I don't have, and I expect few of us possess.

    Yes, the weather is nice, and I have projects piling up....

    I did get my p99 acrylic for my negative carriers in the mail today.
    "No pessimist ever discovered the secret of the stars, or sailed to an uncharted land, or opened a new doorway for the human spirit." - Helen Keller
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  5. #15
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    How about using two of these rails:
    http://www.ebay.com/itm/2pcs-SBR16-3...item231b4e8ddf

    The could be attached to the top of my negative stage, one on each side of the glass plate. A piece of aluminum (or whatever) could be used to connect one of the blocks to a block on the other rail. This would give a bar that could easily be moved from one end of the negative stage to the other. On one side, right above the block, mount a lead screw that goes right above one of the rails to a fixed mounting block just past the end of the rail. Turning the lead screw with a stepper motor would move the cross member along the two rails. That takes care of one axis.

    Attach a lead screw on the cross member, running parallel to it. This would give us the other axis of movement.

    Lead screws could be something like: http://www.ebay.com/itm/12-3-8-16-AC...item19ceec8d3b

    Thoughts?
    "No pessimist ever discovered the secret of the stars, or sailed to an uncharted land, or opened a new doorway for the human spirit." - Helen Keller
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  6. #16
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    Re: DSLR Scanner: Camera Supports and Positioning

    Quote Originally Posted by Peter J. De Smidt View Post
    How about using two of these rails:
    http://www.ebay.com/itm/2pcs-SBR16-3...item231b4e8ddf
    The IKO LWL9 rails that I used could do that, too, and they are much tinier without being in any way weak. But they aren't any cheaper, so this is probably just as good. You'd want two rails and four followers for each direction. I think it would not be too difficult to fasten a pair of rails on four followers for the crossing direction, though it would need some right-angle stiffening unless you can drill holes more precisely than I can. I need a bit of oversize on the holes to allow for alignment--my drill press seems to wiggle just enough to make real precision a challenge. I need to find the runout in that thing and fix it. But I think you'll need very tight holes and precise drilling to use the platforms on those followers to ensure the right angle.

    The rails and sliders I bought only stand 10mm above the deck, but they are so tight that two running in parallel will bind solid if the rails are not parallel to about a thousandth.

    The lead screw looks good. I could mount that easily on my rig if I wanted to automate it. But that's waaaay farther down the road than I'm prepared to go at the moment!

    Rick "wishing the picture of the delrin nut was a little more clear" Denney

  7. #17
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    I get the feeling that the type of system I'm thinking of is overkill for our purposes. After all, my carrier rides on the glass plate, and so the positioning system is only used for x-y motion. I just don't know very much about bearings and so on. There must be something that'd ride on rails made of aluminum angle. The system above would give us accuracy to a few thousandths of an inch, once properly set up, but I don't see the advantages of such a high specification for the workings of our project. The only advantage is that these types of parts are very common in cnc machines, and hence they're readily available.

    By the way, I'm going to have a phone conference with some of the giga macro people tomorrow. They've indicated that they're willing to help us out a bit.
    "No pessimist ever discovered the secret of the stars, or sailed to an uncharted land, or opened a new doorway for the human spirit." - Helen Keller
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  8. #18
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    Here's an idea for a fairly simple to build x-y stage. The bearings would ride in tracks routed on the top of the negative stage. (Or one could use flat strips of abs, aluminum...to make tracks.)
    "No pessimist ever discovered the secret of the stars, or sailed to an uncharted land, or opened a new doorway for the human spirit." - Helen Keller
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  9. #19
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    Instead of the four skate bearings, we could use runners in slots, as one would do for a crosscut sled for a table saw. See product A. at: http://www.leevalley.com/US/wood/pag...455,43831&ap=1 .
    "No pessimist ever discovered the secret of the stars, or sailed to an uncharted land, or opened a new doorway for the human spirit." - Helen Keller
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  10. #20
    joseph
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    Re: DSLR Scanner: Camera Supports and Positioning

    Peter-

    You might not want to hear this, but I think you might be trying to solve a problem that doesn't actually exist-
    I might have to agree with your previous suspicion that it might be overkill...

    Capturing the tiles is the least time consuming part of the process, and introducing further layers of complexity might only lead to unreliability, something else to go wrong. The level of precision needed to align two sets of bearings, whether wheels or sleds, seems to be a little bit unnecessary, given that a plane surface, sliding on another plane surface, should be sufficient in itself. There isn't an actual load that would necessitate any bearings, and planar materials with a low drag coefficient should (does) function very well without them.

    Regarding the xy positioning- well, it's a project, so it would be good if it could be made to work. If you were considering scanning industrial levels of film, then I'd say that it's a goal definitely worth pursuing- to the extent that the negative carrier stage should be made removable, so that you could be loading the next one while the first is being automatically scanned. However, I couldn't justify it myself, since the amount of film I'd want to scan to this resolution is very small.

    Even if, like my friend in Newry, my scanner suddenly stopped functioning, and I decided to do all my scanning with a DSLR, I'd still be quicker by manually positioning the film, rather than waiting for the Epson to complete a high res scan, as I found out the other night.

    I think the main obstacles to be overcome in this project are

    Achieving evenness of illumination,
    consistency of focus between frames,
    finding a lens that has minimal distortion and curvature,
    getting through quite a lot of tedious manual assignment of control points for stitching ( though a more generous overlap would definitely help in this regard)
    and finally, getting rid of the dust.

    Positioning the frame for capture would be at the bottom of this list, for me, though the system I've come up with is very quick and simple, and as I've mentioned elsewhere, the stitching software is completely capable of detecting any anomalies, and compensating for them.

    If large featureless areas are a part of your picture, then dust will inevitably become the feature, and it can be used to help correlate the frames.
    Ultimately, I think the precision you're looking for isn't actually necessary-

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