[Bldg-sim] High Dynamic Range Imaging (HDRI)

[Guglielmetti, Robert]

Hi Sura,

In order to do this you need to include some standard reflectance cards or diffuse samples of known reflectance in the scene, when you take the HDR exposures. From those you can sort-of back out the illuminance at other points in the room, with the caveat that the more specular the surfaces, the less correct that process will be. The idea is that since the HDR image gives you cd/m^2, if you know the reflectance of some pixels, you know how much light fell on those pixels to give you that quantity off of them. Ideally you'd have reflectance standards located at many points of interest about the scene, for this purpose. Again, as the surface gets away from diffuse and more toward specular, your pixel values are less and less representative of hemispherical flux (reflected).

I would highly recommend joining the radiance-hdr mailing list for additional tips (http://www.radiance-online.org/community/mailing-lists/subscribe/hdri).

Also, see these:

lrt.sagepub.com/content/41/1/27.full.pdf

http://www.sciencedirect.com/science/article/pii/S0378778811002982


- Rob



On 12/13/15, 6:20 AM, "Bldg-sim on behalf of Sura Almaiyah" <bldg-sim-bounces at lists.onebuilding.org<mailto:bldg-sim-bounces at lists.onebuilding.org> on behalf of sura.almaiyah at port.ac.uk<mailto:sura.almaiyah at port.ac.uk>> wrote:


Good afternoon,



I'm very much interested in using High Dynamic Range Imaging (HDRI) for recording illuminance values in office buildings as part of Post Occupancy Study. I am using Photosphere software to generate the HDR images, but I am not sure how to convert the luminance values/images to illuminance values.



Any advice would be appreciated.


Many thanks

Sura




Sura Al-Maiyah Ph.D.(Ulster), CIBSE,SLL,ICOMOS

Senior Lecturer, Co-ordinator MA Sustainable Architecture

Portsmouth School of Architecture

University of Portsmouth

t.+44 (0)2392842091