Hi Chris, You would be better off setting the gamma to 2.2. Hdrgen will adjust itself to whatever camera response function is present, but this is closer to the norm and makes better use of the 8-bit code values.
Regarding the Brightness scaling, use 160 and assume this is ASA. Your calculation for iris sounds about right. The main thing is to get the proportions between exposures correct -- the absolute value will be off no matter what you do. The absolute scaling can be corrected by a gray patch luminance measurement and the "Calibrate" function in Photosphere. As long as you keep the inverse linear relationship to exposure time and ASA/brightness and the square relationship to aperture, you will get the relative exposure ratios correct, and this is what matters to the merge operation. -Greg > From: Christian Humann <[email protected]> > Date: April 22, 2012 6:59:00 PM PDT > > Thanks Greg, > > These machine vision cameras have no readout and are driven from a GUI via > USB / Firewire. The GUI I'm using for this particular camera has settings > for: > Gamma .01 - 2.56 (which I set to 1) > Blue Gain 0-1023 (adjusted to get the on screen image as close to grey for > the particular light source under which I'm shooting) > Red Gain 0-1023 > Brightness 160 - 842 ( adjusted to 160 ~I think this is the same as CCD > sensor gain and thus what I need to correlate to ASA) > Exposure .01ms - 3mins (I'm using this to bracket the images) > > The lens I'm using has a manual iris for setting aperture. I'm dividing the > focal length of the lens by the diameter of the aperture to derive the f/stop > value. > > I think I just need to experiment with setting the brightness value to its > lowest setting under a constant light source and see what kind of values i > get from the HDR shots using a constant ASA value in HDRgen and adjusting > this value until I get some agreement between measured brightness and HDR > image brightness. I'f I'm lucky a brightness value setting of 160 will equal > an ASA of 160:) > > Thanks again for you help Greg. Also, thanks to those who replied to my > previous posts on color channel masking...great help! > > Cheers, > Chris _______________________________________________ HDRI mailing list [email protected] http://www.radiance-online.org/mailman/listinfo/hdri
