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Thread: DSLR Scanner: Camera Supports and Positioning

  1. #51
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    You're right. That is pretty extreme. I'm basing it off of the figures at: http://www.edmundoptics.com/products...productid=2482 ,
    and http://www.edmundoptics.com/products...productid=1942. Depth of field numbers are always a bit subjective, as they rely on assumptions about acceptable circles of confusion. I have one of the Mitutoyo 2x objectives, and so I'll be able to test it. It's not like the figures I listed are a cliff and quality drops like a stone if you go outside of it. Rather, you'll start to lose detail in the areas where the height variation increases. As you say, it's very doubtful that most commercial scanners have tolerances that tight.

    You can certainly mount a photo (or something) to a very flat piece of aluminum, but I've been mounting film directly to a thick sheet of glass.
    "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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  2. #52

    Re: DSLR Scanner: Camera Supports and Positioning

    Quote Originally Posted by ludvig friberg View Post

    Do you have any suggestions on what to use for a test subject? I was thinking of printing something and glue it to a pice of aluminum machined on my mill. That will make it parallell to my test setup at least. Maybe I will just print a raster pattern with some numbers to identify and stitch, could be interesting to see how my new printer places the little drops!
    good +

    I used lithos for my 2nd round targets... scratched Numbers into the emulsion --- It felt gooood ---

  3. #53
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    Quote Originally Posted by Peter J. De Smidt View Post
    Our theoretical investigations are pointing to about 300 microns at 1:1 and approximately F8. At 2x things get much, much worse, with a dof of about 9 microns.
    Sorry, that should've been, "At 2x things get much, much worse, with a dof of about 91 microns."

    According to Rik at www.photomacrography.net:

    "It turns out that the "depth of focus" numbers listed by Edmund and
    Mitutoyo do not rest on any assumption about circles of confusion.
    Rather, they are based solely on wavefront error and thus represent
    what would be MTF effects as seen by a perfect analog sensor. In
    addition, their numbers reflect maximum deviation from perfect focus,
    so they give what we might call "single-sided DOF" rather than the
    "total DOF" that is given by classical formulas in photography."
    "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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  4. #54
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    More depth-of-field info, according to The Manual of Close-up Photography by Lester Lefkowitz.
    At 1:1 magnification and an f-stop setting on the lens of F4, the depth of field is 0.48mm. At F5.6, it's 0.67mm, and at F8, it's 0.96mm.
    All of this assumes a maximum circle of confusion of 0.03mm (0.012 in.). That seems a little loose. Some suggest that for an APS-c camera that a better coc is 0.019mm. Using the stricter coc in the DOF formula gives a DOF of 0.43mm at f5.6 on the lens.

    Depth of field (at 1:1) = 4ac
    a= aperture
    c= circle of confusion
    "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. #55

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    Re: DSLR Scanner: Camera Supports and Positioning

    You guys probably already know this but IŽll put this here anyway.

    If you dont have one, get one of these http://littlemachineshop.com/product...ory=1319044103

    and one of these.
    http://littlemachineshop.com/product...ory=1310310429

    You can do a remarkable amount of measuring by using these correctly. Especially if you have a moving table and can mount the indicator to it.

    You can find out x, y and z precision of you table. If you measure on the lensmount on the camera house you can perfectly within microns align the sensor/camerabody to the table, etc. Also the longer travel indicator can be mounted as and used to find precise focus and camera z positions. Then you know how much yuo move the camera (or lens if on bellows)All for 50 bucks.

    http://www.youtube.com/watch?v=VxCvf...eature=related
    do this on x y and z of course.

    Maybe use a surfaceplate is good as a base? You can get a bigger one for a bit more. Like 12" square perhaps $100
    http://littlemachineshop.com/product...ory=1438824943

    if coupled with a heightgage to mount the dslr on it will get VERY square and precise for not too much money
    http://littlemachineshop.com/product...ory=1310310429

    shims can be useful to align perhaps?
    http://littlemachineshop.com/product...gory=758941860

    Anyways the cheap machinist tools offer MUCH higher precision at lower prices. Perhaps a new place to look for ideas for parts?

  6. #56
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    Thanks for the links. Some of that would certainly be useful.

    I have a dial indicator that I use to setup my woodworking tools, as well as various precision straight edges and squares.
    "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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  7. #57
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    Re: DSLR Scanner: Camera Supports and Positioning

    ... this is getting more and more interesting - I really appreciate all the effort you guys put into this!
    A good friend of mine is currently building a CNC cutter himself, so thankfully I'll have some programming and stepper motor knowledge around, when these design evolve even further

  8. #58
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    Update:

    I've been working on tethering my D200 to my Win 7-64 machine. Using Amazon basic cables did not work. Windows did not see the camera. As a result, and on the advice of some knowledgeable folks, I bought a Monoprice 16ft 2 Port USB 2.0 A Male to A Female Active Extension / Repeater Cable for a little over $8. It works fine. I use Control My Nikon to fire the camera using the "delayed exposure" mode, which raises the mirror about 1 second before firing the shutter. CMN sends the file to a folder that Lightroom 4 monitors for auto import. When imported into LR, the file is inverted, and I can compare captures easily. This isn't quite as good as live view, which my D200 doesn't have, but it works well.

    I built an indicator wheel for the knob of my Velmex slide. The 4" diameter wheel has 126 evenly spaced lines along it's perimeter. Since the Velmex lead screw is 20 turns per inch, that means that each tick on my indicator wheel represents a change of 1/2560 of an inch, or 0.000390625 of an inch.

    I placed a 4x5" Bergger 200/PMK negative on the glass sheet and masked off the negative. Using a reversed 55 mm nikkor at exactly 1:1 using some extension tubes, I took a series of exposures a tick of my indicator wheel apart. Exposure was provided by an SB-28 flash at 1/64th power fired into my mixing box. The grain of the film was clearly visible at 1:1. Examining the pictures at 2:1, 21 of the frames were indistinguishable for detail. That means that the depth of field for this combo is 0.008 inches.
    "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. #59

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    Re: DSLR Scanner: Camera Supports and Positioning

    Well... I found a decent deal on a very nice used 150mm El Nikkor so I bought it in the hope that it will perform well for this (reversed). Now I need to find a nice DSLR.

  10. #60
    Peter J. De Smidt's Avatar
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    Re: DSLR Scanner: Camera Supports and Positioning

    If you're using continuous light, look for a Canon with EFCS. See: http://krebsmicro.com/Canon_EFSC/index.html
    "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

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