[Radiance-general] help pfilt and low values dgp
Jan Wienold
jan.wienold at epfl.ch
Fri May 1 08:15:35 PDT 2015
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 <mailto:overduin.jasper at gmail.com>
> *Skype *jasper.overduin
>
> On 30 April 2015 at 13:55, Jan Wienold <jan.wienold at epfl.ch
> <mailto: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 <mailto:overduin.jasper at gmail.com>
>> *Skype *jasper.overduin
>>
>>
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>
> --
> 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
>
>
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--
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
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