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Thread: DSLR Scanner: Stitching and Blending of Images

  1. #1
    Peter De Smidt's Avatar
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    DSLR Scanner: Stitching and Blending of Images

    DIYS (Do It Yourself Scanner—pronounced like ‘dice’)--Stitching and Blending of Images Thread

    Frank Pertronio started this project by suggesting that someone come up with an affordable and contemporary drum scanner, as there is currently huge gap in price and quality between consumer and professional scanners. Domaz suggested using APS-C sensors and using them to take samples of the film, similar to what Gigapan does with large stitched mosaic images. This lead to talk about making a copy stand scanning system using a dslr, a light source and a movable negative stage. Both horizontal and vertical prototypes have been made, or are in the process of being made.

    The original thread has become very long and unwieldy. As a result, I’m creating some new specialized threads for future project development.

    The new build threads are:
    Camera Supports and Positioning,
    Lenses,
    Negative Stages,
    Light Sources,
    Stitching and Blending of Images,
    Cameras and Camera Control Software.
    Workflow.

    These threads are only for positive contributions to the development in the area in question. The project may not succeed, but we’re going to find that out by trying it. But we are not unkind. As the original thread showed, some people have an overpowering urge to say negative things about the project. I’ve created a thread just for this purpose. Please post your negative comments about the project here.

    I would like to thank everyone who makes, or has made, a positive contribution to this project!

    I'll be summarizing the posts from the original thread about stitching and blending of images here soon.
    "Why can't we all just get along?" President Dale, Mars Attacks

  2. #2
    Peter De Smidt's Avatar
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    Re: DSLR Scanner: Stitching and Blending of Images

    A nice article on stitching is: here.
    "Why can't we all just get along?" President Dale, Mars Attacks

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    Re: DSLR Scanner: Stitching and Blending of Images

    Thanks for this.

  4. #4
    Peter De Smidt's Avatar
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    Re: DSLR Scanner: Stitching and Blending of Images

    I've done a little stitching before, but I'm no means an expert. Daniel Moore's help has been invaluable.

    There are a number of ways to assemble all of the images of partial areas of the film.

    1) Manual arrangement using photo editing software. For example, with Photoshop one can put the piece in the difference blending mode and move it with arrow key nudges. When the area goes black, it’s perfectly registered with the layer below it. Once it’s aligned, you can run Photoshop’s auto-blend-layers feature to even out the tones. This works very well, and it leads to very little distortion of the kind that can be introduced by stitching software, but it’s a PITA for a large number of samples. (If you’re not using a large number of samples, this options has a lot of appeal.)

    The following image was put together using method 1.



    2) Stitch the files together using:

    a) Photoshop photomontage.
    b) Microsoft’s Ice. http://research.microsoft.com/en-us/...roups/ivm/ice/,

    The following image was stitched with Microsoft Ice's "structure panorama" feature:



    I expect the problem resulted from one row of the samples overlapping the lower row much more than the other samples did.

    c) PTGui. www.ptgui.com

    Daniel did a nice stitch of the lighthouse with PTGui. See: http://www.largeformatphotography.in...-a-DSLR/page51, post #506.

    d) Autopano Pro or Autopaono Giga. www.kolor.com.
    e) Hugin. Hugin.sourceforge.net.
    f) Double take for Mac OS10 http://echoone.com/doubletake/
    g) PTAssembler. http://www.tawbaware.com/ptasmblr.htm
    h) Imagestack. http://code.google.com/p/imagestack/
    i) Explorable Microscopy. http://www.explorablemicroscopy.org/ There's lots of interesting stuff here.
    j) Panorama Tools. http://wiki.panotools.org/

    Some comments on the options:
    1) Most of us already have it. It does a very good job with blending.
    2)
    a) Doesn't do well with a complex stitch.
    b) Ice is very fast and simple, but it’s not really editable. So if you get a stitch with a missing or misplaced part, there’s little you can do. It’s free.
    c) The is a very feature rich program. Like most stitching software, it assumes rotational camera motion, wheras we would prefer linear. Changing the lens characterisitcs as per Daniel Moore’s suggestions help. (He suggestions listing the lens used as a 1000mm one.) It costs $110.
    d) These are also very feature rich. Giga doesn’t allow an align to grid function without particular robotic heads.
    e) It’s free! But as far as I can tell, one has to enter control points manually, which is a huge pita. It’s also been a bit unstable on my Windows 7- 64 bit machine, the only program which as that problem.

    I haven’t investigated the other options yet. So far, the results seem to be that stitching files covering a piece of film that has detail through out isn't hard, but doing so with a film that has large areas without detail is much more challenging. We've been able to get some good results, but it takes quite a bit of work.
    "Why can't we all just get along?" President Dale, Mars Attacks

  5. #5

    Re: DSLR Scanner: Stitching and Blending of Images

    I threw Peter's lighthouse images into the experienced and capable hands of the PTGui Support Google Group simultaneously requesting adding fine image nudging control to PTGui program. Two experts there Erik Krause and John Houghton both offered that the 'featureless' areas as I took to referring to sky areas as, contained enough markings to in fact place control points there. Their results bore this out handily. So simply because a sky area doesn't stitch automatically, one can always go in and at 100% zoom level, add points as needed to get things to align.

    For the sake of demonstration, here's a result of John Houghton's stitch efforts done in PTGui.

    Click image for larger version. 

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    It's apparent in this image that Peter's light source is doing a very respectable job and that PTGui seems to be blending images nicely. Also worth noting, the original negative Peter provided was a long exposure in windy conditions - manually adding control points is therefore not dependent on critically sharp images, but rather critically sharp DSLR captures at the scanning stage. In theory, a perfect stitch could be made from the blurriest of images using only defects in the film emulsion, so dust and hair are your friends.

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    Peter De Smidt's Avatar
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    Re: DSLR Scanner: Stitching and Blending of Images

    Daniel, that does look very good. Where there any other tips besides manually adding some control points?
    "Why can't we all just get along?" President Dale, Mars Attacks

  7. #7

    Re: DSLR Scanner: Stitching and Blending of Images

    Here's one of Erik Kraus' replies:

    Manual fine tuning will never be as precise as control point driven
    stitching. The reason is that a correction on one side will make
    alignment on the other side worse.

    Although http://www.ptgui.com/support.html#5_6 works, it's better to use
    viewpoint correction for this kind of stitching, since this is not a
    panorama but a mosaic shot from different viewpoints (same as shooting a
    long mural).

    See Thread "Some nice big mosaics" for details:
    https://groups.google.com/d/topic/pt...JzA/discussion


    It appears the Viewpoint Correction in the pro version is advised, I'll download a trial as I don't have that version and see if it helps.

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    Re: DSLR Scanner: Stitching and Blending of Images

    Are the source files still available. I tried: http://dl.dropbox.com/u/3595413/Ligh...02nd%20try.rar but that no longer seems valid?

    Thanks.

  9. #9
    Peter De Smidt's Avatar
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    Re: DSLR Scanner: Stitching and Blending of Images

    Hm. That's funny. They seem to be gone. I didn't remove them. In any case, I re-uploaded them. Try: http://dl.dropbox.com/u/3595413/Ligh...02nd%20try.rar
    "Why can't we all just get along?" President Dale, Mars Attacks

  10. #10
    Peter De Smidt's Avatar
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    Re: DSLR Scanner: Stitching and Blending of Images

    I modified my negative guide so that I could do 25 samples of equal size on the 6x7cm negative, and I ran them through Ice, Giga, and PTgui. Please remember that I'm not a stitching expert.







    Microsoft Ice was by far the fastest. This was a structured panorama with planary 1 positioning. This option is for stitches with changes in camera position, as opposed to stitches based on rotating the camera. Obviously, there were a few stitching flaws, but the blending appears to be the best of the three. It wouldn't be hard to take this file into Photoshop, load the files for the mis-aligned pieces, align them, and use auto-blend-layers. You could do all of this in less time than that other two methods. (Although I saved a template in PTgui. It'll be interesting to see how this works on my next 6x7cm negative scan.)

    It wasn't hard getting Ptgui and Giga to give a pretty good stitch, but it took the addition of quite a few control points manually.

    My conclusion is that although there are some issues, stitching will work, even with difficult negatives. It should be a breeze with shots with overall detail, or with shots with many less samples.

    Obviously, this area could use more work, but now it's a question of refinement and not feasibility.

    I'm going to turn my attention to other matters, such as building a better negative carrier, and then I'll start testing lenses. (I've also started to look into the automation question.)

    I'll be happy if I never see that negative again.
    "Why can't we all just get along?" President Dale, Mars Attacks

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