I just built a fixture for doing noise tests. The glue is drying, it's being held in place with masking tape, but shots of the setup as I was building the light trap and target board are posted at: http://www.flickr.com/photos/ellarsee/sets/72157621826942359/
(They are quick and dirty shots, with even quicker processing, using the on camera flash for most of them, so they look like crap, but you can see how it's made) For the tests themselves, I realize that I'll want to have at least white, at near clipping, (18%) grey, and black. For the black, I built a light trap, and if I light the target from the side, inside the light trap should be pretty close to total dark, which will give me a good signal floor for measuring, or at least seeing, noise. Since one of the effects of noise reduction can be a loss of sharpness, I expect that somewhere in the frame I'll want some sort of resolution target. What I plan on doing is printing up a target, and make some small cards with details like ISO, f/stop, shutter speed, which camera. The target board is set up at a 2:1 slope, which will make it easy to set the camera up parallel to it so the target will all be in the same plane of focus. Can anyone point me to a graphics file that I can print up on my laser printer with a suitable target? Also, if anyone has any suggestions for how to run the test, I'm interested in your ideas. What I'd love is a program that I could give a JPEG, or a PEF and get back a measurement of the SNR, though I suspect with images you are interested in both the amplitude of the noise, and the percent of pixels that have that much noise. Also SNR may not be as appropriate as amplitude (in bits), and average amplitude (in bits). lrc -- The first step is learning to take great photos, the second step is learning to throw away ones that are merely good. Larry Colen [email protected] http://www.red4est.com/lrc -- PDML Pentax-Discuss Mail List [email protected] http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
