Dear all: Sorry to bring up this topic again, but I run into the same issue Coltide has (Coltide's original post is here: http://radiance-online.org/ community/mailing-lists/archives/hdri). I also use Canon 5D 2 with SIMGA Fisheye lens 8mm f/3.5. I want to figure out the -C factor when using raw2hdr to combine LDR images. I took the images (f/11) under different circumstances: two HDR images were taken along a side window, two images were taken under electric lighting condition, and the last one were taken far away from a glazing. For each scene, 12 images were taken and assembled. The luminance values from the HDR images and the lighting meter are below (cd/m2): Side window: 123.0(HDR) 225.0(measurement) 1.83(-C factor) Side window: 101.0(HDR) 195.4(measurement) 1.93(-C factor) Electric light: 1.9(HDR) 3.3(measurement) 1.74(-C factor) Electric light: 1.4(HDR) 2.6(measurement) 1.79(-C factor) Away from glazing: 9.8(HDR) 18.5(measurement) 1.88(-C factor)
Questions: 1) I can average the results (1.84) as the correction factor, but is it correct? Some values have great difference (1.74 VS 1.93). 2) I notice that I use the same model as Coltide, however, our results are very different. Is this normal? (The production of each camera and lens cannot be exactly the same?) 3) Does lighting source influence the accuracy of the factor? Focusing on daylighting data collection, should I take images under consistent electric lighting conditions or daylighting conditions? (Daylighting conditions have dynamic changes, but electric situations offer lower results.) Any suggestion or comment is appreciated. -- *Zhe Kong* *PhD Student* *University of Wisconsin - Milwaukee * *School of Architecture and Urban Planning * *2131 E. Hartford Ave, Milwaukee, WI 53211 * *Office 327*
_______________________________________________ HDRI mailing list [email protected] http://www.radiance-online.org/mailman/listinfo/hdri
