| CGTechniques.com |
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| Christian Bauer; 8/2001 | |
From Fisheye to a HDRI
This Tutorial is for all ppl with a Nikon 950/99x and a fisheye. With that Fisheyelens you are able to photograph more than the half Enviroment at once...so why not using it if we only need the sky for HDRI's?
We look verticaly into the sky with the camera, heads down ;), and makes
Images from 1/1000 to 1/2 sec.
The problem with this methode is that you look into the sun and that you
will always get very bright Images, that's why you will get not really
"complete" HDRI's.
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Now you have Images with different exposuretimes. |
The Images will looks like this:
1. Now crop the image to have a aspect ratio of 1:1.
There is one big problem with the Fisheye from Nikon: Chromatic aberrations as described at H.Dersch's page or also called Color seperation.
Have a look at the images in detail;
2. You can try to correct it with Panotools and with settings like below,
but you may get better results with other settings because it's depending
on your camera.
This is the result of the operation, even a little bit better:
3. What's next?
We now only have to convert the image from polar projection to rectangular
projection. This sounds strange but it will work also for our vertical
fisheye and you don't need Panotools and can do it with the normal Photoshopplugin.
You now have a spherical Panorama but only from the horizon to the zenith. (or little beyond because the fisheye have a horizontal angle from 183-187°..depends on the optic) All you now have to do is some rescaling and resizing:
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If you do this with all your images and save them as TGA and name it similar the exposuretime(up_1000.tga,up_500.tga .... up_15.tga) you can write a script for mkhdr and use it for every set. |
My set looks like this:
mkhdri.txt:
oben_1000.tga 1000 7 3 0
oben_500.tga 500 7 3 0
oben_250.tga 250 7 3 0
oben_125.tga 125 7 3 0
oben_60.tga 60 7 3 0
oben_30.tga 30 7 3 0
oben_15.tga 15 7 3 0
oben_8.tga 8 7 3 0
oben_4.tga 4 7 3 0
This file will be called by this Batchfile which runs mkhdr:
mkhdri.bat:
mkhdr.exe -w dummy mkhdri.txt sternwarte.hdr
where "-w dummy" is a
dummyfile to prevent mkhdri crashing and "sternwarte.hdr"
the outputfile.
That's it.....