Luminance vs illuminance on valutation field (road lighting)

questions regarding the handling of DIALux evo. (features, tools, options, settings)
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sunlightstorm
Posts: 8
Joined: Tue Sep 08, 2015 9:30 pm

Luminance vs illuminance on valutation field (road lighting)

Post by sunlightstorm » Wed Dec 09, 2020 11:25 am

Dear staff,
I have a question concerning road lighting.
Maybe I misinterpreted something, but when I switch from M class to C class (perhaps for the presence of a conflict zone), I get results that leave with some doubt.
If I look at the results on an M4 (luminance), I see an irregular distribution of the data.
Image

If I look at the results on a C3 (illuminance), I can see the symmetry on the isolux.
Image

Should not I see some symmetry also on the Luminance map? I mean, for Lambertian surfaces the formula relates the two values: L = ρ ∙ E / π
Is this due to the specularity factor of the road? Or something I’m missing?

Thank you very much

Sun

Csuleiman
Posts: 2083
Joined: Wed Mar 07, 2012 3:07 pm

Re: Luminance vs illuminance on valutation field (road lighting)

Post by Csuleiman » Wed Dec 09, 2020 1:01 pm

Hello Sun,

For the category of an M luminance class, the observer-dependent luminance is calculated at the individual assessment points, with the observer standing on one of the lanes 60 metres from the start of the field. So there is no symmetry here, but if a different lighting class (e.g. P4) is selected for evaluating illuminance, the field is completely symmetrical. This is best seen from the isolines in the documentation, which are available separately for horizontal illuminance and luminance (as seen by both observers).

Best regards,
DIAL Support Team

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