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Thread: Making a scanner with a DSLR

  1. #541
    Peter J. De Smidt's Avatar
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    Re: Making a scanner with a DSLR

    Donald, I commented on your post in the other thread.
    "There are no rules here - we're trying to accomplish something." - Thomas A. Edison
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  2. #542
    Peter J. De Smidt's Avatar
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    Re: Making a scanner with a DSLR

    I'm going to take an extended sabbatical from this project. I have other more pressing matters to attend to. It looks like others have this project well-in-hand, and I leave it to them.
    "There are no rules here - we're trying to accomplish something." - Thomas A. Edison
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  3. #543
    Mike Anderson's Avatar
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    Re: Making a scanner with a DSLR

    Quote Originally Posted by Peter J. De Smidt View Post
    I'm going to take an extended sabbatical from this project. I have other more pressing matters to attend to. It looks like others have this project well-in-hand, and I leave it to them.
    Well I think your achievements so far are impressive and it's been fun and interesting to watch. Enjoy your break.
    Mike → "Junior Liberatory Scientist"

  4. #544
    joseph
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    Re: Making a scanner with a DSLR

    Peter- you deserve a rest- you've been driving this thing for a long time, and the results are looking good.

    It's nearly time for me to dust off my apparatus, which was substantially completed by the end of January, according to the exif on the pictures I took to record the process-

    I did some tests at the time, but I was getting a lot of vignetting, and I need to revisit it, and try to sort it out.

    John, in NYC, the thing I built will easily take the larger negative, up to 11x14, or 12x20-
    However, as soon as I had it built, I wished I had made a dinky little 4x5 version.

    That's the MKII, and it's on the drawing board, along with countless other projects-

  5. #545

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    Re: Making a scanner with a DSLR

    This is an interesting thread. I didn't read it all, so I hope this hasn't been mentioned already. Anyway, a while back, I was researching this whole thing and after looking at everything I could find online in the way of tests, I came to the conclusion that of all the common macro lenses for DSLRs in the 60-105mm range, the Sigma 70mm f/2.8 Macro had the best sharpness from corner to corner and seems to be quite free of distortion. I never did make the purchase though, so I haven't tested it in this application. But it is an option worth looking at I think. Coupled with one of the Sony 24MP APS-C sensors, it seems that a lot of detail could be recorded. One caveat though, as I seem to remember reading that Sigma has some quality control issues and that performance of these lenses varies quite a bit from sample to sample. So if you buy one and it isn't so great, don't blame me!

  6. #546
    Peter J. De Smidt's Avatar
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    Re: Making a scanner with a DSLR

    "There are no rules here - we're trying to accomplish something." - Thomas A. Edison
    www.peterdesmidt.com/blog

  7. #547
    Mike Anderson's Avatar
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    Re: Making a scanner with a DSLR

    Quote Originally Posted by Peter J. De Smidt View Post
    Interesting. More info.

    Looks like they're doing automated focus stacking and stitching.
    Mike → "Junior Liberatory Scientist"

  8. #548
    Peter J. De Smidt's Avatar
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    Re: Making a scanner with a DSLR

    Here's a link on digitizing 16mm film. http://www.pc-control.co.uk/film-digitiser.htm
    "There are no rules here - we're trying to accomplish something." - Thomas A. Edison
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  9. #549

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    Re: Making a scanner with a DSLR

    I'm coming to this a bit late, but have a few pointers that might be of interest.

    Here's how to do the job properly: http://hea-www.harvard.edu/DASCH/scanner.php

    This was a scanner built to digitise astronomical glass plates, with stringent requirements for spatial and densitometric calibration, and with a high throughput. The technical paper linked from that page is worth reading, and the video is fun to watch (and dream about). I don't know what the whole setup cost, but some points are worth noting for a homebrew effort.

    First, and I don't think anyone has mentioned this yet, a telecentric lens helps solve many issues. It pretty well eliminates vignetting, and it ensures that the digital image of the film always has the same magnification even if the negative is bowed in the holder. I haven't done detailed calculations yet, but it's probable that at 1:1 imaging you can eliminate refocussing altogether.

    There are commercially available telecentric lenses with the right characteristics, but most of them are incredibly expensive by homebrew standards. The insect focus stackers seem to like the Cosmicar 55 mm, which is a C-mount lens but covers well enough at 1:1 or more. It is also possible to jury-rig your own telecentric aperture for a regular macro lens - see this discussion on a macro forum - and it's linked threads - for some ideas

    http://www.photomacrography.net/foru...pic.php?t=1032

    The second point is that eliminating spatial patterns with repeats equal to the step-size of the scanner is always hard, even with the best equipment. If you don't have the option of detailed calibration (and temperature control to keep the calibration constant) the best solution is to take photos on a finer grid - the redundancy helps with blending. The limiting case of this would be to take a video of the film scanning continuously under the camera (a technique used in spectral detectors for nulling out the small variations in response from pixel to pixel) but I suspect you'd lose resolution that way.

    The third point, is that film handling, cleaning, loading and unloading, and writing the catalogue entries will take as much time, if not more, than making the scan. It makes sense to have more than one negative holder or scanning platen so that you can be loading a second sheet while the first is scanning. This, more than the bragging rights of a robot stage, is why I would regard automated movement - on one axis at least - as essential.

    I applaud the efforts of those who have actually tried this for real. At the moment my investigations are at the stage of working with my daughter and her Lego Mindstorms kit on a scanning table, and tinkering with the lenses I have in the house to see if I can get a workable telecentric lens arrangment without having to spring for a megabuck macro lens.

  10. #550
    Peter J. De Smidt's Avatar
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    Re: Making a scanner with a DSLR

    Hi Struan,

    Good stuff. Thanks for posting.
    "There are no rules here - we're trying to accomplish something." - Thomas A. Edison
    www.peterdesmidt.com/blog

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