[Radiance-general] help pfilt and low values dgp
J. Alstan Jakubiec
alstan at jakubiec.net
Tue Aug 11 08:33:38 PDT 2015
Hi Jasper,
This is one of the tricky aspects of doing glare analysis with your own
HDR images. A couple of pointers are below,
* You will need to crop your image to a square aspect about the image
center using the pcompos
<http://radsite.lbl.gov/radiance/man_html/pcompos.1.html> tool.
There was a helpful discussion on maintaining image exposure values
while doing this here
<http://www.radiance-online.org/pipermail/radiance-general/2011-March/007701.html>.
* The -vv and -vh parameters are just best guesses according the HDR
generation software. Once you have cropped the image, you will want
to open the resulting HDR in a text editor and manually change the
header 'VIEW' field to include -vta -vv 180 -vh 180. You may also
specify them via the command line at this point, as you have done. I
like to keep it associated with the image.
* After that, unless I am forgetting something (others can chime in),
you are ready to run evalglare. I would run it with the -d flag,
which will report a lot of details. Most usefully, it reports
illuminance as derived from the image, which you can compare to your
measured Ev value to check the validity of the HDR. If your HDR is
well-calibrated, not inputting the measured illuminance value should
be perfectly accurate.
* I suspect that inputting measured illuminance is somewhat broken in
the current version of evalglare as I have the same problem that you
do. One option is to use the -1 option to evalglare, which will
return only a single DGP value. It seems to avoid this error.
> evalglare -1 -i 2500 image.hdr
By the way, to avoid some of this cropping and exposure value pain, I
use an image-processing tool (like PIL for Python) these days that can
maintain EXIF data while cropping the source jpeg files. Though perhaps
the cure is worse than the disease in this case..
Best,
Alstan
On 8/11/2015 11:08 PM, Jasper Overduin wrote:
> 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 <mailto:overduin.jasper at gmail.com>
> *Skype *jasper.overduin
>
> On 1 May 2015 at 12:15, Jan Wienold <jan.wienold at epfl.ch
> <mailto: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 <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
>>>
>>>
>>> _______________________________________________
>>> Radiance-general mailing list
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>>> http://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
>>
>>
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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
> LE 1 111 (Office)
> Phone +41 21 69 30849
>
>
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