The 400 megapixel project: part 3

January 20, 2009 | Category: How To...., Photography

With life in the way, I have really been neglecting the scanner camera project for the last couple months. I finally found myself with time today and figured I’d do a short progress report. Since my last project post, I’ve designed a primitive focusing and framing back that is pretty accurate. I’ve also made some progress on the banding (effectively eliminating roughly 60-75% of the horizontal banding). I describe the process after the break.

The first field test of the scanner camera. This is cropped and has not had any banding reduction. Notice the odd way that motion is recorded.


Banding reduction: The Basic Idea
(1). Compose, focus and take a “normal” frame of the scene.
(2). Without moving the scanner, place some white diffusion material (heavy cotton without texture) over the lens. Evenly illuminate the cotton and take a second frame. This is simply a photo of the banding and imperfections of the scanner. This is the “bias” frame. The idea comes from astrophotography, where bias frames are used to remove spots and dust on CCD cameras as well as objects such as planes in the sky.
(3). In Photoshop, place the bias frame in a layer on top of the normal frame.
(4). Invert the bias frame layer and change the blending mode to color dodge.
(5). making sure the photo is rotated so that any remaining banding is horizontal, de-interlace both odd and even lines.

an illustration of the banding reduction technique

Before and after banding reduction - up close
    a crop from a 1200 dpi, 70 megapixel scan

If anyone has any ideas on removing the remaining banding, please let me know. More updates to come…

The 400 Megapixel Project – Part 1

The 400 Megapixel Project – Part 2

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3 Comments

  1. Jim Belosic
    on January 25th, 2009
    1

    Beautiful work. We’re always looking to outsource to good talent.

    Jim Belosic
    Belosic|ADG – A Reno, NV Advertising Agency

  2. Tim
    on January 30th, 2009
    2

    I’m amazed at the detail and how sharp the image is. I had thought of doing something like this a while back but don’t have the 8×10 camera.

    As for your vertical banding. It reminds me of when I would have to photograph TV screens to be used in a newspaper I worked for. One of the tricks I began doing to make the photo look a little better in the end was a slight shift to out of focus so the dot pattern wasn’t so prevelant and moire problems would disappear.

    In a similar vane perhaps duplicating the image and shifting it left or right by 1 pixel and using a 10% overlay, or another filter that would just brighten the dark areas. I can’t remember the photoshop filters off the top of my head. I’m not sure if this would degrade the image much or not.

    Something in the back of my head says there is a way to fix the banding, but I cannot remember for the life of me how to do it. I just keep thinking it was an issue we had to deal with when we were using our very first digital cameras for newspaper photography. We used a NC2000E which was basically a Nikon N90 body attached to a tank that doubled or trippled the height of the camera. The images were horrible compared to modern cameras. Highlights would shift pink if they were overexposed. It was ugly.

  3. Marcio
    on November 10th, 2009
    3

    I’m looking foward to see your progress here. I’ve seen this before but haven’t found as much detailed information about it as you are doing.

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