[Radiance-general] help pfilt and low values dgp

Tue Aug 11 08:08:03 PDT 2015

Dear all,

I have changed my lens to one with 180 circular view to do a contrast
analysis (hdrscope) and meanwhile the glare analysis in evalglare. If i use
the commands in evalglare getinfo i get the (HDR composed with photosphere
on a mac, calibrated with luminance pistol) i get a value for the lens -vv
and -vh which is not over 100, with a lens of 180. I can imagine that the
photo ratio and the lens are not the same and that causes this problem. But
when I enter the external measured Ev, the value the dgp goes somehow to
zero. The fact that the gdp is zero with a maximum luminance of 5600 cd/m2
and Ev of 2500 lux makes me a bit suspicious. How accurate is the result of
the dgp without external vertical lux? is it possible to use this value?

hdr files and printscreens of evalglare
https://www.dropbox.com/sh/ei1y4d2v6hapdsr/AACgVMPd1o0EdK-0q8CFvUGga?dl=0

Greetings Jasper

*Jasper Overduin*
MSc. Building Technology graduate student at Delft University of Technology

*S* Groenhoevelaan 3
*P* 2343 BP Oegstgeest
*T* +31 6 15 64 48 56 (NL)
*T* +56 9 51 11 76 48 (CL)
*E *overduin.jasper at gmail.com
*Skype *jasper.overduin

On 1 May 2015 at 12:15, Jan Wienold <jan.wienold at epfl.ch> wrote:

> Hi Jasper,
>
> I briefly looked at your image - for sure you get a low DGP value if your
> illuminance at camera (or eye) level is only about 300lux... It is not the
> matter of the fish eye lens it is a matter of your lighting condition.
> When I remember correctly, for the experiments I did for my PhD, the
> people adjusted the blinds in a way, that they had 2500-3000 lux at the eye
> level and they were less than 20% of them dissatisfied. So a value of 300
> means one order of magnitude less light at the eye level and a much lower
> adaptation level.
> So I definitely understand the low DGP value in that case. The images
> themselves look reasonable, so I don't think there is a problem in
> calibration/processing so far (at least not for these low luminance
> levels-it might be more tricky to calibrate for the high luminance values
> when you get stray-light from the multiple lenses).
>
> If all your images are like that it means you have a very low daylight
> contribution at the place you measure. I'm not sure if DGP is then the
> right way to measure glare in that case - as I wrote it is made more for
> the daylight oriented workplace with higher levels and also to take into
> account very high luminances (e.g. sun or specular reflections of the sun).
> DGP might be modified in future, but these experiments are just starting.
>
> Jan
>
>
>
>
>
>
> Am 4/30/15 um 10:41 PM schrieb Jasper Overduin:
>
> Thank you for the fast reply. We are still having some problems with the
>> outcome of Evalglare. With an external luxometre we have done some tests
>> now. The DGP is still very low or zero. It seems that in almost all the
>> case the DGP is low. In literature we read that values above 20% are
>> normal. What do you think? is the data much better if we use a full 180
>> degree lens?
>>
>> .hdr file https://www.dropbox.com/s/l10x7tri49btr8r/ff.hdr?dl=0
> print screen cmd
> https://www.dropbox.com/s/yv1lamhiirjhvxq/imp%20pan.jpg?dl=0
> test.pic https://www.dropbox.com/s/nspdu01477mchsz/test.pic?dl=0
>
>
>> Greetings Jasper
>>
>>
>>
>>
>>
>> *Jasper Overduin*
>> MSc Building Technology graduate student at Delft University of Technology
>>
>> *S* Groenhoevelaan 3
>> *P* 2343 BP Oegstgeest
>> *T* +31 6 15 64 48 56 (NL)
>> *T* +56 9 51 11 76 48 (CL)
>> *E *overduin.jasper at gmail.com
>> *Skype *jasper.overduin
>>
>> On 30 April 2015 at 13:55, Jan Wienold <jan.wienold at epfl.ch> wrote:
>>
>>> Hi Jasper,
>>>
>>> why are you using -vth -vh 140 -vv 80 when in your header of the HDR
>>> image the view is specified as  -vtv -vh 98.797409 -vv 75.402067 ?
>>> Manipulating the lense type is really dangerous - in that case you
>>> change from a perspective view to a hemispherical fish eye view, without
>>> changing the image!!
>>>
>>> If I apply evalglare for your image I get 0.17 as DGP (which is still
>>> very low, but you have only 2000cd/m2 as maximum value, so this can be
>>> expected). Be aware, that DGP accounts only for glare from a high amount of
>>> daylight and/or spots of extreme luminances (>50000cd/m2), but not for
>>> contrasted glare between task (e.g. Monitor) and immediate surroundings for
>>> lower adaptation levels. This is subject of current research (also here at
>>> EPFL) and there might be an extension of the DGP in future, depending on
>>> the outcome of new experiments.
>>>
>>> Back to the lens-type:
>>> It is extremely important, that the right view type is given to
>>> evalglare, otherwise ALL calculated values (it doesn't matter if this is
>>> evalglare or findglare) are wrong. These errors could be huge, more than
>>> 100% for calculating the illuminance out of a 180 degree image.
>>>
>>> If you manipulate an image by pcomb, in general the view is marked as
>>> "invalid" in the header, because with that tool you could manipulate the
>>> image in a way, that the original view is not valid any more. This is why
>>> from evalglare version 1.0 on a check on the header was included, because
>>> many people were creating wrong headers without knowing it and then
>>> evalglare was calculating wrong values, when the header was invalid.
>>>
>>> In addition for calculating the DGP it is important to have the
>>> illuminance at camera level. evalglare calculates this value out of the
>>> image. But if the image does not cover 180 degree, then the calculated
>>> value for the illuminance is too low. For that reason, the -i option was
>>> included, so you can provide the illuminance to evalglare (when you measure
>>> it with an illuminance sensor).
>>>
>>> So in your case, you should measure the illuminance just besides the
>>> lens.
>>> Then (in case this is the right lens description) you should use
>>> evalglare -i LUXVALUE -vtv -vh 98.797409 -vv 75.402067 IMAGE_NAME
>>> or better, if your task is always at the same place:
>>> evalglare -i LUXVALUE -vtv -vh 98.797409 -vv 75.402067  -T 395 230 .6 -c
>>> CHECK_FILE_PICTURE IMAGE_NAME
>>>
>>> good luck!
>>>
>>> Jan
>>>
>>>
>>>
>>> Am 4/30/15 um 6:04 PM schrieb Jasper Overduin:
>>>
>>> Somehow cant use the command pfilt or change the pcomb, does this has to
>>> do with the program Radiance? I have installed the version of windows from
>>> the site, with evalglare v1.11windows . The problem is that I have composed
>>> a .hdr (out of 7 jpg on a mac) and after using the command
>>> c:/HDRI>evalglare -vth -vh 140 -vv 80 image.hdr all the dgp results are
>>> really low, less than 5%. The problem can be in the .hdr (calibrated as
>>> well) or is in the way evalglare is not working as it shoot on my computer.
>>>
>>>
>>>
>>> *.hdr file* (post-it is calibration point 167,98)
>>> https://www.dropbox.com/s/4z69y358yt8ii4z/1_sv_am.hdr?dl=0
>>> *images* original
>>> https://www.dropbox.com/sh/adyyxjkv6eykyek/AAC96QUTpLh_Ef2U8Mppki8ta?dl=0
>>> *command printscreen*
>>> https://www.dropbox.com/s/0pbn105p0z0iinu/Imp%20pan.jpg?dl=0
>>>
>>>
>>> Need the help!
>>>
>>> Greetings Jacobus
>>>
>>>
>>> *Jasper Overduin*
>>> MSc Building Technology graduate student at Delft University of
>>> Technology
>>>
>>> *S* Groenhoevelaan 3
>>> *P* 2343 BP Oegstgeest
>>> *T* +31 6 15 64 48 56 (NL)
>>> *T* +56 9 51 11 76 48 (CL)
>>> *E *overduin.jasper at gmail.com
>>> *Skype *jasper.overduin
>>>
>>>
>>> _______________________________________________
>>> Radiance-general mailing listRadiance-general at radiance-online.orghttp://www.radiance-online.org/mailman/listinfo/radiance-general
>>>
>>>
>>> --
>>> Dr.-Ing.  Jan Wienold
>>> Ecole Polytechnique Fédérale de Lausanne (EPFL)
>>> EPFL ENAC IA LIPID
>>> http://people.epfl.ch/jan.wienold
>>> LE 1 111 (Office)
>>> Phone    +41 21 69 30849
>>>
>>>
>>> _______________________________________________
>>> Radiance-general mailing list
>>> Radiance-general at radiance-online.org
>>> http://www.radiance-online.org/mailman/listinfo/radiance-general
>>>
>>>
>>
>
>
> _______________________________________________
> Radiance-general mailing listRadiance-general at radiance-online.orghttp://www.radiance-online.org/mailman/listinfo/radiance-general
>
>
> --
> Dr.-Ing.  Jan Wienold
> Ecole Polytechnique Fédérale de Lausanne (EPFL)
> EPFL ENAC IA LIPID
> http://people.epfl.ch/jan.wienold
> LE 1 111 (Office)
> Phone    +41 21 69 30849
>
>
> _______________________________________________
> Radiance-general mailing list
> Radiance-general at radiance-online.org
> http://www.radiance-online.org/mailman/listinfo/radiance-general
>
>
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