Hi Yulia, Since your maximum values are tracking the differences in your shorter exposures, it seems to indicate that you still haven't captured the brightest point on the LED. What are you looking at that makes you think the exposures have nothing over 200?
There is no harm in the newer version of hdrgen in including exposures that are too dark or too light. More naive methods might have trouble with this, but not hdrgen or raw2hdr. Best, -Greg > From: "Tyukhova, Yulia" <[email protected]> > Date: March 1, 2012 12:46:29 PM PST > > Hello! > > I've been experimenting with the number of photos to include in final HDRI. > > I took a sequence of photos of a single LED with reflectance standards > included in the scene. > EOS7D 28-105mm lens at 28mm > F16 1/8000-1/15’’ > F4 1/30-5 mins > With the ND filter t=0.0094 > Images are fused with raw2hdr. > They were calibrated at white reflectance standard 215 cd/m2. > I’ve noticed the following tendency: > If I fuse different number of photos (cut the number of photos on the > shortest end), after calibrating at white reflectance standard, I get > different luminance values for the LED. > Shortest exposure to fuse L,cd/m2 > 1/125’’ f16 4.5*106 > 1/250’’ f16 9.06*106 > 1/500’’ f16 18*106 > > I've seen interesting discussion between Axel and Greg on photos to include. > But it seems like there are many uncertainties. > > In HDRI second edition book it says "The darkest exposure should have no RGB > values greater than 200 or so, and the lightest exposure should have no RGB > values less than 20 or so. Do NOT include an excess of exposures beyond this > range, as it will do nothing to help with the response recovery and may hurt." > I assume it is the same for any HDRI sequence, not only for response curve. > > I have plenty of photos of dark exposures that have no values greater than > 200, same with the light exposures and 20.If somebody can clarify what photos > should be included or have any other suggestions that would be great > > Thank you, > Yulia
_______________________________________________ HDRI mailing list [email protected] http://www.radiance-online.org/mailman/listinfo/hdri
