HDRI creation

[polygun]

http://www.cgtalk.com/search.php?s=

[dongallant]

So I geuss that's a no? I have tried to look for information all over the net posting on several Forums, I've read Paul Debevec's papers and all techniques use many exposures with Digital cameras to (I assume) "fake" 16bit images...I've emailed Paul Debevec hoping that he can shed some light on this subject.

P.S. Thanks for your suggestion though to SEARCH the forum...I would have never thought of that....you rock! :applause: :thumbsup: :annoyed:

[Marcel]

The tutorials on Devebecs site are very in-depth, they certainly contain enough information to do some tests to make you find out what you need. I advise you to just experiment, it's fun to do (god, are we geeks or what :) ) and you'll find out much more about it than asking people.

To answer some of your questions: yes, you need more than one exposure, thats what HDRI is all about. You take multiple photos each with the shuttertime halved so that you photograph a very broad spectrum of light:

1/30 sec - very overlit, but with good detail in the dark areas
1/60
1/125
1/250
1/500 sec - very underlit, but with good detail in the bright areas.

In practice you would/could also use the aperture to control light.

When you assemble these images in HDRI shop you'll end up with a image with a very high range, with details in the darkest areas but also in the lightest.

If you scan your mirrored ball photo and save it as a 16-bit cineon image you will not have a hdri image, because the information was not in the photos in the first place.

[dongallant]

THANK YOU! I was starting to think it was a dumb question or something...hahaha..

I have experimented with using a digital camera and have been sucessfull. But...I worded my post wrong, what I am doing is having my Negatives scanned into a 16bit cineon...so the information should be there, I was able to get a demonstration shown to me and it actually has a wider range than the compiled digital photos...that's why I assume I only need to use one frame instead of a range. From what I've read on Debevec's site, the only reason you need the multiple photos is to emulate a 16bit image when they are compiled...This method is used becuase HiRes scanning is so expensive. I'm going to try it and see what happens...Thanks again for your reply..

[jyrgen]

Please read carefully through Marcels post and Debevecs site again and again and again, because you still got it totally wrong. The whole point of HDRI is not being 16 or whatever bits deep, but containing information on energy of particular lighting situation, which is only possible using different exposures. You could scan or photograph an image using 64 or 128 bits for every channel, but it only gives you a very accurate representation of colour, but no info on energy, i.e. no HDRI. You just can't create HDRI from one frame. As already explained by Marcel.

[Marcel]

Using real film negatives is a bad idea for making HDRI images.
The amount of work is much bigger: scanning all those images, cropping them, placing the exposures exactly on top of eachother etc etc.
Apart from that you scanner will probably try to correct the whitepoint and black point of your photo. If you scan a very dark photo it will try to get the color values in a decent range, destroying the meaning of the exposure.
HDRIshop is assuming each exposure has twice the amount of light, if the scanner changes the values that won't be correct anymore.

So use your digital camera, and yes jyrgen is right, you still have to do multiple exposures for a HDRI, you cannot create a HDRI from one shot not even with real film and a gazillion bit scanner.

[Egyt]

http://www.cgtechniques.com/tutorials/hdrenviroment.php

[CapnPanic]

http://www.hello-napalm.com/tuts/tut_hdri.html

and another :D

[dongallant]

Thanks again guys....nice work Capn_Panic....

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