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 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.


sourceimages Now you have Images with different exposuretimes.


The Images will looks like this:
a closeup of one sourceimage


1. Now crop the image to have a aspect ratio of 1:1.
Crop the image


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;
detailed problem


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:
a bit better result

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.
remap it with polar->retangular


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:

resize it



resulting sources 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:

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:

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.....


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