[Radiance-general] conversion of digital pictures to Radiance?

[Barbara Matusiak]

Thanks for the heads up!

I'm in the process of choosing a camera and the Digital Rebel seems to be a 
fine choice indeed. However I would like some more background info on the 
file formats. I can't seem to be able to dig up much on what the "raw" 
format actually contains, I imagine it isn't necessarily the same from 
camera to camera? Are there parameters to be passed on to the hdr 
generating software based on the raw format?

I have no support for macosx, so it's between windows and linux, although 
the hdrgen program looks interesting as it's command line based and easier 
to enter into batch processing. But I couldn't find any documentation about 
it and the executable doesn't have any built in help whatsoever. :)

Could I possibly ask you to roughly describe the process of generating hdr 
images from those taken with the Rebel? Any calibration involved?


Barbara


At 10:38 28.05.2004 -0400, you wrote:
>Barbara Matusiak wrote:
>
>>I wonder if it is possible to convert pictures taken by digital camera to 
>>Radiance format? And if yes, how it could be done? The Radiance format 
>>enables reading of luminance values directly from the pictures, something 
>>that could be very usefull in the project I plan to start soon.
>
>Yes, but only if you shoot the images in a specific manner and convert 
>them to high dynamic range (HDR) format first.  A single image does not 
>contain the dynamic range necessary for what you want to do.  But for 
>typical scenes, if you simply bracket your exposure (using aperture, not 
>changing shutter speed) by two F stops in each direction, you can use 
>utilities like Debevec's HDR Shop or Greg Ward's Photosphere (or his 
>command-line hdrgen) to merge those into an HDR image with the full 
>dynamic range.  You can then use Radiance tools like falsecolor (and even 
>pcond) to extract real luminance information from a photograph.
>
>We use a Canon Digital Rebel here in my office to create these image 
>sequences.  The autobracket function of the camera is very useful for 
>this.  Many "prosumer" cameras have this feature, but you must make sure 
>the camera will separate the images by two f-stops.  Of course you can do 
>it manually too, but then you usually need a tripod to keep everything in 
>registration.  You also need to "go manual" to capture scenes of really 
>high dynamic range, using more images to capture the full range.
>
>I've been meaning to place some samples on my website, but haven't had 
>time.  But these resources are better anyway:
>
>http://www.anyhere.com/
>http://www.debevec.org/HDRShop/
>
>HDR photography is extremely cool.  You can even use HDR images as light 
>sources for Radiance scenes!  Santiago Torres of this list has done quite 
>a bit of work in that.  Search the radiance-general archives for 
>details.  Have fun!
>
>----
>
>      Rob Guglielmetti
>
>e. rpg at rumblestrip.org
>w. www.rumblestrip.org
>
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associate professor Barbara Matusiak                            Tel.: +47 
73 59 50 77
Faculty of Arcitecture and Fine Art                             Fax: +47 73 
59 53 88
Norwegian Univ. of Science and Technology 
(NTNU)                barbara.matusiak at ark.ntnu.no
N-7491 Trondheim, 
Norway 
http://www.ab.ntnu.no/byggekunst/ansatte/ansattesider/bam.html