Hi Chris,
Thanks for writing. If you want to subscribe to the HDRI mailing list at radiance-online, here is the URL:
http://www.radiance-online.org/mailman/listinfo/hdri
It's generally pretty quiet, but this sort of discussion is very welcome.
The warnings you are seeing in Photosphere are just that -- they are just my way of saying, "If the output looks funny, it's not my fault." In particular, the 'Trouble Finding HDR Patch' warning is nothing to worry about. It just means some of your exposures are very dark or very light, and there's not much information to be gleaned from them in deriving a camera response. The same is usually true of the alignment warning, though small, bright objects like light sources may show double-images if the camera wasn't mounted on a tripod. If it was, then you should probably turn alignment off altogether. In the latest version of Photosphere, turning alignment off kicks in a new feature to remove "hot pixels" from the output.
If you are not deriving the camera response for the first time, during on 'Skip Extra Exposures' in the dialog is a good idea, since it will avoid most of these problems. In fact, you shouldn't see the 'Finding Patches' error at all if you use a saved response function. Hopefully, this is working for you, as following the hints in quickstart_pf.txt (part 12) and reusing a saved response is the best way to avoid problems.
I should mention that it doesn't really help the process to include exposures that have no dark pixels (values all over 20) and no bright pixels (values all under 200). You can use Photosphere's histogram viewer to check this and exclude extreme exposures. This will help reduce the number of warnings.
Best,
-Greg
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From: "Christopher Simmons, Mr" <[email protected]>
Date: May 27, 2008 11:33:37 AM PDTDear Dr. Ward,
First of all, let me begin this e-mail by saying I am a huge fan of your work. I was wondering if you could refer me to some resources that address an issue I am having with your photosphere program. I am creating HDR images, and for some I have the recurring problem of "Trouble Finding HDR Patch" and "Exposure too extreme for alignment." When I took the photo series used in the HDR image, I went from 1/4000 s to 30 s exposure times. That is, I double the exposure time for each photo between 1/4000s to 30s (standard procedure), but I took a few extra exposures in between to be on the safe side and included these in the final HDR image. Does the "Exposure too extreme for alignment" message indicate that there was an extra exposure, so it was removed? Or does it mean that an exposure was brighter or darker than necessary for the HDR image and was eliminated? And how do these messages affect the final output? When I get these messages, how does it affect the luminance values obtained, or relative luminances between different pixels in the same image? If it has a negative impact on luminance, should I create the HDR in another program (photoshop, HDR shop, etc) and then analyze it in yours?
Any resource you may be able to mention discussing these issues would be greatly appreciated. Thank you for your time and attention.
Sincerely,
Chris Simmons