[Radiance-general] Faulty fisheye HDR, DGP always 1.0

Wed Feb 14 02:10:44 PST 2018

Hi Jan and Greg,

Thank you very much  for your  suggestions. Finally the issue seems to be solved. It is true that the problem is  in HDR generation process. We divided each of the pixel values by 179, then HDR seems to be in  radiance compatible format. Now the results of these HDR images from Evalglare are more meaningful.

Once again I thank you for your effort. 

Best Regards,
Raghu

> On Feb 6, 2018, at 7:31 PM, Jan Wienold <jan.wienold at epfl.ch> wrote:
> 
> Hi Raghu,
> 
> The spot luminance measurements should ideally be done for several ranges for each HDR capturing (e.g. one reference area with 100cd/m2, another one with several thousands) and finally you compare the illuminance of the image with the measured one and you should reject any image with a deviation larger than 25% deviation of the illuminance. With a proper calibration you can be also within 10%.
> 
> Definitely the luminances of your image are totally off (=physically impossible, at least factor  50 for the blue sky) - it has nothing to do with evalglare. 
> BTW. evalglare calculates the illuminance also for that image (617414.88 lux) - there is no limit or "out of bounds". Just that your image has much too high luminances, so you get also an unrealistic illuminance... 
> It is hard to tell where the problem lies exactly, but definitely it is caused by your applied  hdr generation process.
> 
> Cheers
> Jan
> 
> On 06.02.18 18:57, Raghuram Kalyanam wrote:
>> Hi Jan,
>> 
>> We did the calibration and the results of spot luminance measured and calculated from HDR for the light source (calculated with custom made tool )  is very close. 
>> 
>> I want to compare the measured  Vertical eye illuminance with the one calculated with evalglare, but the results are out of bounds from evalglare, so i couldn't even compare. 
>> 
>> Could you suggest me anything  else i should be taking care of? Any ideas. 
>> 
>> Best Regards, 
>> Raghu
>> 
>> 
>> 
>> On Feb 6, 2018 6:24 PM, Jan Wienold <jan.wienold at epfl.ch> <mailto:jan.wienold at epfl.ch> wrote:
>> was it taken on mercury ? ;-)
>> the luminances are far off... it sums up to more than 600000 lux 
>> Jan 
>> 
>> 
>> On 06.02.18 18:18, Greg Ward wrote:
>> Hi Raghu,
>> 
>> We may need to wait to hear from Jan or someone who understands evalglare better than I do.  I don't think there is a problem with your HDR image as you generated it.
>> 
>> -Greg
>> 
>> From: raghuram kalyanam <kalyanam at rhrk.uni-kl.de <mailto:kalyanam at rhrk.uni-kl.de>>
>> Date: February 6, 2018 9:05:41 AM PST
>> 
>> Hi Greg,
>> 
>> I added these options while passing to evalglare like below.
>> 
>> evalglare -vta -vh 180 -vv 180 <hdr file>, and it worked but it always gives 1.0 as DGP (even other parameters are out of bounds).
>> 
>> With out those options evalglare throws an error.
>> 
>> Apart from that
>> 
>> Are all the LDR’s provided, valid to combine into HDR?
>> 
>> I doubt if one or more of the LDR’s is the culprit (especially something to do with over or under exposure).
>> 
>> Best Regards,
>> Raghu
>> 
>> On Feb 6, 2018, at 5:05 PM, Greg Ward <gregoryjward at gmail.com <mailto:gregoryjward at gmail.com>> wrote:
>> 
>> Hi Raghu,
>> 
>> It looks like your HDR image header is missing the necessary view information.  Typically, this might be something like:
>> 
>> VIEW= -vta -vh 180 -vv 180
>> 
>> for a perspective such as yours.  You should be sure that your fisheye mapping corresponds to one of the standard Radiance types.
>> 
>> Best,
>> -Greg
>> 
>> From: raghuram kalyanam <kalyanam at rhrk.uni-kl.de <mailto:kalyanam at rhrk.uni-kl.de>>
>> Date: February 6, 2018 5:21:59 AM PST
>> 
>> Hi All,
>> 
>> I am trying to asses visual discomfort  using fisheye HDR images. We generated HDR image from a set of 360 degree LDRs and then converted to fisheye HDR ( using a custom made tools). The intension was to use these Fisheye HDRs as input to Evalglare and get DGP value. The Camera used is Ricoh Theta V 360 degree camera.
>> 
>> The problem I am facing is, the DGP calculated from the generated fisheye HDR with Evalglare is always 1.0. We did the calibration but I would like to have expert opinion from you people, what is going wrong with these set of images. Here is the link <https://seafile.rlp.net/f/0212995d110648d38032/?dl=1> to the pictures.
>> 
>> It would be great if anyone could identify the issue.
>> 
>> Best Regards,
>> Raghu
>> 
>> 
>> 
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>> -- 
>> Dr.-Ing.  Jan Wienold
>> Ecole Polytechnique Fédérale de Lausanne (EPFL)
>> EPFL ENAC IA LIPID
>> 
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>> 
>> 
>> 
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> 
> -- 
> Dr.-Ing.  Jan Wienold
> Ecole Polytechnique Fédérale de Lausanne (EPFL)
> EPFL ENAC IA LIPID
> 
> http://people.epfl.ch/jan.wienold <http://people.epfl.ch/jan.wienold>
> LE 1 111 (Office)
> Phone    +41 21 69 30849
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