[Radiance-general] Tone mapping for animation

[Greg Ward]

I don't use hdr2jpeg myself, and it isn't distributed with Radiance.  Depending on which version you have, it applies either a Reinhard TMO or a variant of the histogram adjustment operator in pcond, but there's no way to tell it to use a specific curve as you can with the pcond -I option Jack mentioned.  The latter technique with phisto is what I generally use if I want a sequence exposed the same.  And, you can go on using the same histogram for future frames so long as they don't change too much from the range of past frames.

Cheers,
-Greg

> From: David Geisler-Moroder <david.moroder at gmail.com>
> Date: October 22, 2013 8:50:27 AM PDT
> 
> Hi Jack,
> 
> I guess Greg is the only one to answer that question.
> However, I guess some tone mapping has to be done as the HDR-JPG format is backwards compatible and all viewers that read JPGs also read that. So somehow they need to get get the tonemapped information...
> 
> Cheers,
> David
> 
> 
> 2013/10/22 Jack de Valpine <jedev at visarc.com>
> Hi David,
> 
> Great, glad it helped!
> 
> I have not used the hdr2jpeg utility so I am not really sure what it does. My impression is that it converts to a jpeg that contains hdr information. I do not think that it does tone mapping though. Perhaps others can weigh in...
> 
> 
> Best,
> 
> -Jack
> -- 
> Jack de Valpine
> President
> 
> Visarc Incorporated
> www.visarc.com
> 
> channeling technology for superior design and construction
> On 10/22/2013 11:14 AM, David Geisler-Moroder wrote:
>> Hi Jack, hi Lars,
>> 
>> thanks a lot for the quick response!
>> Jack, your second hint exactly did what I was looking for. I tried to use pcond first, but didn't think of the possibility to use a histogram...
>> 
>> Sorry, if my description was somehow cryptic, but you exactly found what I wanted...
>> 
>> Just for information: the pfilt exposure corrections do not help in my case because the tone-mapping that is done in the HDR2LDR conversion (with hdr2jpeg / ra_tiff or similar) does the tone mapping for each single frame independent from the other images. (But maybe I just got something terribly wrong here...!?)
>> 
>> Thanks!
>> David
>> 
>> 
>> 
>> 2013/10/22 Jack de Valpine <jedev at visarc.com>
>> Hi David,
>> 
>> I am a little unclear on what you want to accomplish but here are a few thoughts.
>> time series animation with constant exposure on successive frames - use pfilt -1 -e [constant exposure setting] for each frame
>> time series animation with tone mapping function on successive frames - use pcond and phisto, phisto will compute a histogram across a series of frames pcond can then use the results from phisto to tone map the frames according to selected tone mapping operator, there is a an example in the man page for pcond
>> I think that maybe where I am confused by your description is that since Radiance output is already HDR, setting exposure is really a post process. I think that what you are looking for is the second option that I describe above.
>> Not sure if this answers your questions, but perhaps gives you some things to look into.
>> 
>> Best,
>> 
>> -Jack
>> -- 
>> Jack de Valpine
>> President
>> 
>> Visarc Incorporated
>> www.visarc.com
>> 
>> channeling technology for superior design and construction
>> On 10/22/2013 9:45 AM, David Geisler-Moroder wrote:
>>> Hi all,
>>> 
>>> I have a question concerning the tone mapping procedures implemented in the Radiance tools. 
>>> For an animation of a full day I would like to get something similar that a camera would do that just takes a picture every 5 minutes with the same settings (exposure time and aperture). Rendering the images for every 5 minutes is not a problem, however, I stuck when trying to convert the HDRs to some tonemapped images. As far as I got it, In ra_jpeg/hdr2jpeg no exposure can be given at all, in ra_tiff/ra_bmp only relative exposures can be applied.   
>>> 
>>> Thus my question: is it possible to explicitly set the exposure used in the tonemapping process with any tool in Radiance?
>>> 
>>> Thanks in advance!
>>> David
>>> 
>>> 
>>> 
>>> _______________________________________________
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>> 
>> 
>> 
>> 
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