Dear all, I am using a Canon EOS 5D Mark II with a Sigma EX DG 8mm f/3.5 fisheye lens to capture LDR images. I then use hdrgen with the response curves I defined previously to generate HDR images from these LDR images. I calibrate the HDR images for the vignetting effect and the distortion (equisolid to equidistant projection). Finally, I apply a calibration factor of around 1.39.
When comparing the vertical illuminance and luminance values of the HDR images with the real measures I took (Minolta LS-110 luminancemeter and Hagner EC1-X luxmeter), I noticed that the HDR images are underestimating the illuminance (e.g. 1217lux instead of 1993lux) and the high luminance values (e.g. 208 cd/m² instead of 402.3cd/m²). I determined the illuminance value of an HDR with Evalglare -V and the luminance values with ximage in Radiance. I also tried only applying default hdrgen (+cropping & header modification to set the VIEW to vta to use in Evalglare) but I still got big differences between the HDR-derived and the measured luminance and illuminance values. Is somebody using the same instruments I am? If yes, do you also happen to have this issue? Or does anybody have already encounter this problem? Thank you for your insights ! Best, Clotilde [Test] Clotilde Pierson FNRS PhD Fellow | Arch. Eng. Architecture et Climat Faculté d'architecture, d'ingénierie architecturale et d'urbanisme (LOCI) Université catholique de Louvain (UCL) Place du Levant, 1 bte L5.05.04 B-1348 - Louvain-la-Neuve (Belgique) [email protected]<mailto:[email protected]> Tél. 32 (0)10 47 91 52 - Fax 32 (0)10 47 21 50 http://www.uclouvain.be/architecture-climat.html
_______________________________________________ HDRI mailing list [email protected] http://www.radiance-online.org/mailman/listinfo/hdri
