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