Hi all, Thank you for raising this topic and sharing your views. I¹m using the output of a Sigma f=4.5mm F/2.8 for several analysis including DGP via Evalglare that should require a -vth or -vta view, so this is critical information for me. May I ask why people refer to -vth as equi-solid angle and not hemispherical as it is defined in Radiance¹s rpict man page? My understanding from that page and from Axel Jacobs' presentation sent via the link just before is that there isn't a Radiance description for the equi-solid angle view.
Best Regards Raquel Viula PhD Researcher TU Delft | Faculty of Architecture and the Built Environment | Architectural Engineering and Technology Julianalaan 134, 2628 BL Delft, The Netherlands | P.O. Box 5043 2600 GA Delft From: Claus Brøndgaard Madsen <[email protected]> Reply-To: High Dynamic Range Imaging <[email protected]> Date: Friday 27 January 2017 13:49 To: High Dynamic Range Imaging <[email protected]> Subject: Re: [HDRI] Convert equisolidangular to equiangular projection Hi everyone, Some years ago I tested my Sigma 8mm lens, f3.5. At the time I found several sources online claiming it to be equi-solid angle (-vth), but it didn¹t match my personal experiences with the lens, so I tested it. My tests showed it to be equidistant (-vta), i.e. identical to the angular fish eye projection in RADIANCE. So, in my experience, the 8mm Sigma lens is equidistant. Cheers, Claus Claus B. Madsen Assoc. Prof., Ph.D. | Department of Architecture and Media Technology Phone: +45 9940 8788 | E-mail: [email protected] <mailto:[email protected]> Aalborg University | Rendsburggade 14 | 9000 Aalborg | Denmark Employee No.: 107255 | Vat No.: DK29102384 From: "J. Alstan Jakubiec" <[email protected]> Reply-To: High Dynamic Range Imaging <[email protected]> Date: Friday, 27 January 2017 at 11.33 To: "[email protected]" <[email protected]> Subject: Re: [HDRI] Convert equisolidangular to equiangular projection A little followup that is worth noting is that Axel Jacobs measured the Sigma 4.5mm and found it to have an equi-solid angle projection. See his presentation here: https://www.radiance-online.org/community/workshops/2012-copenhagen/Day2/Jac obs/Jacobs-AJ09-HDR_Radiance_WS-2012.pdf Alstan On 1/27/2017 6:26 PM, J. Alstan Jakubiec wrote: > Hi Tobias, > > I just purchased a pair of Sigma 8mm f/3.5's for my work, but I haven't > measured them for vignetting and angular verification yet. It is on my to do > list :). I will be disappointed if they are equi-solid angular however. Will > let you know sometime after the Lunar new year. > > Alstan > > > > On 1/27/2017 6:17 PM, Tobias Porsch wrote: >> Hi Alstan, >> >> I'm not sure if your below description is correct. >> In my experience it's exactly the opposite. The Sigma f=8mm F/3.5 lens is an >> equi-solid angle (-vth) and the Sigma f=4.5mm F/2.8 is an equi-distant >> (-angular) (-vta) lens. >> Can you please double-check that issue for me? >> >> Cheers >> Tobias >> >> >> Von: J. Alstan Jakubiec [mailto:[email protected]] >> Gesendet: Donnerstag, 26. Januar 2017 06:58 >> An: [email protected] >> Betreff: Re: [HDRI] Convert equisolidangular to equiangular projection >> >> Hi Zhe, >> >> As far as I am aware, the Sigma 8mm f/3.5 is an equi-angular (-vta) lens, and >> the Sigma 4.5mm f/2.8 is an equi-solid angle (-???) lens. I am having trouble >> finding a source from Sigma right now, but Cauwerts, Bodart and Deneyer's >> paper <http://www.tandfonline.com/doi/abs/10.1582/LEUKOS.2012.08.03.002> >> says so. >> >> That said, if you do end up with an equi-solidangle image, I have a python >> script that converts equi-solid angle to equi-angle for each source jpeg >> while maintaining the EXIF data. I used this to convert equi-solidangle >> images from my Canon 8-15mm fisheye lenses. >> >> Best, >> Alstan >> >> On 1/26/2017 8:48 AM, Gregory J. Ward wrote: >>> Hi Zhe, >>> >>> You should be able to apply the fisheye_corr.cal file I gave you earlier to >>> correct the distortion and make it an angular fisheye image that pinterp >>> works with. (Why you need pinterp, I am not sure.) The command is as >>> suggested in the fisheye_corr.cal file itself: >>> >>> pcomb -f fisheye_corr.cal -o fisheye.hdr \ >>> | getinfo -a "VIEW= -vta -vh 180 -vv 180" \ >>>> > corrected.hdr >>> >>> This will also crop the area outside of 180° to black, assuming that is what >>> you want. It assumes that you have already cropped the image to a minimum >>> square area. You should apply vignetting correction and absolute >>> calibration first. >>> >>> Cheers, >>> -Greg >>> >>>> From: Zhe Kong <[email protected]> <mailto:[email protected]> >>>> Date: January 25, 2017 1:15:49 PM PST >>>> >>>> Dear list: >>>> I am trying to compare HDR images and simulated luminance maps. Since I use >>>> SIGMA 8mm 1:3.5 for Canon, I need to convert equisolid-angular to >>>> equiangular project. I see very useful information from the post below: >>>> >>>> https://www.radiance-online.org:447/pipermail/radiance-general/2015-August/ >>>> 011184.html >>>> >>>> However, I still have some questions need to figure out. >>>> 1) pinterp does not include equisolid-angular projection, so a equation >>>> needs to be applied to the function. Greg mentioned this simple expression, >>>> sin(theta)/theta, but I am still confused. Could anyone offer me the >>>> command? >>>> >>>> 2) The post discussed the steps of processing HDR images. If I get it >>>> right, the steps following "adjust exposure" are vignetting correction, >>>> adding view information, converting project from equisolidangular to >>>> equiangular, then calibrating the image. I use a GOSSEN Starlite 2 to >>>> record the luminance value on a grey card for calibration. My question is, >>>> should I calibrate the image before or after converting fisheye projection? >>>> >>>> Any suggestions or explanation would be appreciated. >>>> Zhe >>>> >>> >>> _______________________________________________ >>> HDRI mailing list >>> [email protected] >>> http://www.radiance-online.org/mailman/listinfo/hdri >> >> >> >> >> _______________________________________________ >> HDRI mailing list >> [email protected] >> http://www.radiance-online.org/mailman/listinfo/hdri > > > > > _______________________________________________ > HDRI mailing list > [email protected] > http://www.radiance-online.org/mailman/listinfo/hdri _______________________________________________ HDRI mailing list [email protected] http://www.radiance-online.org/mailman/listinfo/hdri
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