very strange UGR calcuation

crashes, error report
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Joined: Mon Jun 10, 2013 12:31 pm

very strange UGR calcuation

Post by deech123 » Wed Dec 09, 2020 6:50 pm

Dear guys,

I'm facing a serious problem that I can not solve and also do not understand at all.
we have an LDT file from the test lab, where we can see that in the photometric report, section : UGR (Unified Glare Rating) TAble that all numbers are between 14 and 19.

when we do a calculation, we use reflections values of : 77% ceiling, 70% walls and 25% floor as client asked.
after calculation we end at the 20.3
But if we look at the ugr report, we can see this is only for 2 places, where you can not even think of why....the rest is all 12/15/16.

is there anybody that has any clue why this is like this, since we tested with other suppliers their low ugr lights, and we have the same problems in that?
I installed the latest version of EVO 9.1, but still the problem is there and we (also some other guys I know that uses Dialux Evo a lot).
in the attachments you can see the UGR screenshot where this happens and also in the second attachment(UGR2) you can see the lights, the points and I marked the 2 exeptions in red circle.
UGR calculation is set as : Height = .8m, step = 15°, angle from 0° to 360°
building is 2.5m in height( lamps are at 2.5m),

we tested even other lensens from others that claim to have UGR<15 and also with them we have spots that peak at UGR<20
UPDATE : I also included the UGR table from the IES file, where you can clearly see that it's low...

we are totally lost and do not know what else to do, then ask it here to be sure the problem are not inside Dialux.
UGR3.JPG (131.55 KiB) Viewed 1087 times
UGR1.JPG (138.18 KiB) Viewed 1109 times
UGR2.JPG (80.95 KiB) Viewed 1109 times

Posts: 2115
Joined: Wed Mar 07, 2012 3:07 pm

Re: very strange UGR calcuation

Post by Csuleiman » Wed Dec 16, 2020 9:39 am

Hello deech 123,

The UGR table is calculated on a very specific situation described in the standard. There are a lot of restrictions and definitions to be taken into account, if you want to calculate a table.

Definitions, limitations and parameters that have always to be taken into account:

- No UGR in exterior lighting
- No UGR in Road lighting
- You can calculate UGR, but it makes no sense if you have luminaries with an indirect light output ratio above 65%
- Calculation can only be done for luminaries in the field of view above 90° viewing angle
- Calculation can only be done for luminaries within the positions defined for the “position index by Guth”

Definitions, limitations and parameters that have to be taken into account for the table:

- Only one type of luminaires
- Only rotational or two axis symmetric luminaires
- Only rectangular room
- No obstruction
- Fixed spacing (spacing to height ratio either 0.25 or 1)

DIALux is handling the UGR calculations exactly according to the CIE document 117, discomfort glare in interior lighting.

The UGR values can be calculated according to a formula (please see ... 116115-ugr). This is the way it is done for the UGR calculation grid and for the UGR calculation points.

If a client asks for the UGR value, he normally does it because of the EN12464 Lighting of workplaces – indoor workplaces. It is stated in this standard (chapter 4.4.1.), that the values from the table method should be used. If a table can’t be calculated, that’s it. It is not defined in this case. That means UGR does not make sense. You could use an UGR calculation grid or an UGR calculation point but that’s not what the client ask for.

- Do not provide UGR calculations or tables for exterior luminaries, it makes no sense
- If you have an interior luminaire and it should be symmetrical (either rotational or two axis) the LDC you put into the database should be symmetrized (No software can recognize that, it has to be done by the photometric lab)
- Yes the UGR calculation (surface or point) is depending on the observers position and viewing direction
- If you want to know UGR in all directions you need a lot of points/surfaces
- 1.2m is the standard height for a sitting observer

Some basics about UGR are given in the PDF and besides this, you will also find some general information about the UGR method: ... gr-method/

Best regards,
DIAL Support Team


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