Sorry about the confusion I brought up. I got this wrong information from the manufacturer. If I recall my previous experience, Sigma f/3.5 matches Radiance -vta pretty well. The current mismatch might be caused by the camera coordinate in the simulation. Anyway, Happy Chinese New Year, everyone!
Zhe On Fri, Jan 27, 2017 at 10:11 AM, <[email protected]> wrote: > Send HDRI mailing list submissions to > [email protected] > > To subscribe or unsubscribe via the World Wide Web, visit > http://www.radiance-online.org/mailman/listinfo/hdri > or, via email, send a message with subject or body 'help' to > [email protected] > > You can reach the person managing the list at > [email protected] > > When replying, please edit your Subject line so it is more specific > than "Re: Contents of HDRI digest..." > > > Today's Topics: > > 1. Re: Convert equisolidangular to equiangular projection > (Gregory J. Ward) > > > ---------------------------------------------------------------------- > > Message: 1 > Date: Fri, 27 Jan 2017 08:10:53 -0800 > From: "Gregory J. Ward" <[email protected]> > To: High Dynamic Range Imaging <[email protected]> > Subject: Re: [HDRI] Convert equisolidangular to equiangular projection > Message-ID: <[email protected]> > Content-Type: text/plain; charset="windows-1252" > > Raquel points out an important error in this discussion's terminology. > The "equidistant" fisheye does indeed correspond to the "-vta" view type in > Radiance. However, the "-vth" type corresponds to a hemispherical > projection, which very few commercial fisheye lenses realize. In > particular, the equisolidangle projection is much closer to "-vta" than it > is to "-vth". If your lens is equisolidangle, then you need to use the > fisheye_corr.cal script or similar to convert it to an equidistant > projection. > > I have not implemented the equisolidangle projection, though there is a > third fisheye type (-vts) which is called "stereographic", although we > prefer the term "planisphere" projection to avoid confusion with stereo > views. This does not correspond to any commercial lenses to my knowledge, > but I'd be interested to hear of one. > > > From: Raquel Viula <[email protected]> > > Date: January 27, 2017 5:49:57 AM PST > > > > Hi all, > > Thank you for raising this topic and sharing your views. I?m 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 Radiance?s 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 Br?ndgaard 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 didn?t 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] > > 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/Jacobs/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 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]> > > 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 _______________________________________________ > > HDRI mailing list > > [email protected] > > http://www.radiance-online.org/mailman/listinfo/hdri > -------------- next part -------------- > An HTML attachment was scrubbed... > URL: <http://www.radiance-online.org/pipermail/hdri/ > attachments/20170127/f2bd1701/attachment.html> > > ------------------------------ > > Subject: Digest Footer > > _______________________________________________ > HDRI mailing list > [email protected] > http://www.radiance-online.org/mailman/listinfo/hdri > > > ------------------------------ > > End of HDRI Digest, Vol 87, Issue 6 > *********************************** > -- *Zhe Kong* *PhD Student* *University of Wisconsin - Milwaukee * *School of Architecture and Urban Planning * *2131 E. Hartford Ave, Milwaukee, WI 53211 * *Office 327*
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