Hello everybody! I appreciate your help and responses.
Greg, I've been checking histograms with CANON Digital Photo Professional. I was checking L channel, I guess I need to make sure RGB values are below 200 as well. Are there any suggestions on this issue? Martin, That is a very interesting suggestion! I guess I can see the difference between the measurements of two light sources. >> ..the photopic sensitivity curve V(lambda) currently used is incorrect. It underestimates blue wavelengths quite a bit. >> You should really use a CCD camera with a photopic filter to get better values.. You say that V(lambda) underestimates the values. But doesn't CCD camera's photopic filter have the same response curve? So, it would have the same mistake. Lars, >> Did you derive the response curve of your camera using another setup (not the directly visible LED) and reuse that camera response later on your LED captures? Or do you take the camera response from the same set of images (showing the LED in an otherwise dark room) that you are going to assemble into a HDR? I've tried two approaches. The first one is to derive the response curve from the scene with very dark and bright areas with smooth gradients and neutral colors. Then fuse them to obtain RC. And then I've used it in photosphere for subsequent HDRIs. And the second one is to fuse raw images with Greg's script raw2hdr, where you don't have to have response curve. Greg: "The raw2hdr script doesn't need to derive a response curve, since the sensor data is linear. Instead, it creates an output from dcraw that follows a 2.0 gamma and creates an artificial response curve of x^2 to decode it. This reduces quantization errors from the 8-bit intermediate images". And then I can analyse my hdr image in Photosphere. -- Thank you, *Yulia Tyukhova* * * Fulbright Scholar, "Intern LC" Architectural Engineering Graduate Student, UNL-Omaha, NE, USA B.E. and M.E. in Lighting Engineering (MPEI), Moscow, Russia [email protected] [email protected] +1 (402) 996 0910 PKI 247
_______________________________________________ HDRI mailing list [email protected] http://www.radiance-online.org/mailman/listinfo/hdri
