Different results in IES and LDT files of the same light source

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usisseven
Posts: 4
Joined: Wed May 30, 2018 11:10 am

Different results in IES and LDT files of the same light source

Post by usisseven » Mon Jul 09, 2018 1:25 pm

Hello everybody,

I came across a light source which has both ies and ldt files from the producer company. I have tested the light sources in the same simple room in Dialux to test to see if there is any difference. I have realized that there is a small difference between two results. Can anyone tell me the reasons for that?

you can find the light source i used under this link:
https://norka.de/de/products/phalanx-62 ... trahlend-1

and my results in a screenshot:
ldt-ies-norka-dialux.png
ldt-ies-norka-dialux.png (101.13 KiB) Viewed 926 times
and I can send the example project I did per personal message.

Thank you for your help!

Okan

T.Magenheimer
Posts: 1236
Joined: Thu Jul 26, 2012 10:16 am

Re: Different results in IES and LDT files of the same light source

Post by T.Magenheimer » Tue Jul 10, 2018 5:02 am

Dear Okan,

We wonder if you could provide us with the evo project file. Our email address is 'Support@dial.de'.
Please send us also the link to this topic, so that we could better assign this issue.


Best regards,
DIAL Support Team

usisseven
Posts: 4
Joined: Wed May 30, 2018 11:10 am

Re: Different results in IES and LDT files of the same light source

Post by usisseven » Tue Jul 10, 2018 7:14 am

Hello,

I have sended the project file to your email adress!

thank you!
Okan

F.Krewett
Posts: 68
Joined: Mon Jul 06, 2015 2:16 pm

Re: Different results in IES and LDT files of the same light source

Post by F.Krewett » Tue Jul 10, 2018 12:10 pm

Dear Okan,

This is a typical question caused by missing information of LDT or IES files. Please find below the explaination for the different calculation results.

IES files contains no information about the luminiare housing or the position of the light center in the housing. To support those files in DIALux as well we have implemented an assistant which allows the user to enter the correct vlaues for the housing. By default the shape and dimmensions are set to the sahpe and size of the light output. The default height is set to 0,1m or if available to the height of the light emitting surface.
Import assistant.png
Import assistant.png (28.98 KiB) Viewed 912 times
The LDT file contains information of the housing but no information of the position of the light center as well.

In your project both photometric files are imported with a different height of the luminaire case. Therefore the light center height is also different which has impact on the calculation result of course.
LightCenterHeightIES
LightCenterHeightIES.png
LightCenterHeightIES.png (19.42 KiB) Viewed 912 times
LightCenterHeightLDT
LightCenterHeightLDT.png
LightCenterHeightLDT.png (19.31 KiB) Viewed 912 times
If the height of the light center is the same for both luminaires the calculation results will be the same too.
To avoid such confusions and to receive more accurate calculation results for this and other possible reasons we recommend to use the ULD format instead of IES or LDT. The ULD format is an extended photometric format which contains much more information to describe a luminaire more precise. You can find the required ULD e.g. on LUMsearch.com
https://lumsearch.com/de/article/nKssQr ... hrw?_Y=220


Best regards
Fabian

usisseven
Posts: 4
Joined: Wed May 30, 2018 11:10 am

Re: Different results in IES and LDT files of the same light source

Post by usisseven » Wed Jul 11, 2018 7:33 am

Dear Fabian,

but I do not understand, as these files should be used for the same reason and result the same. When I convert the files myself using a third party software, same thing happens. I have also noticed that the dimentions aren`t the same but why does that happen? I got those files from the producer theirselves.

Thank you,
Okan

F.Krewett
Posts: 68
Joined: Mon Jul 06, 2015 2:16 pm

Re: Different results in IES and LDT files of the same light source

Post by F.Krewett » Tue Jul 17, 2018 9:03 am

Dear Orkan,

As explained above is the height of the luminaire housing not included in the IES file format. The manufacturer themself cannot enter the height in the IES format too. All information about the housing cannot be displayed. The IES file just describes the light emitting surface. This is a weak point of this format.

But to support IES files in DIALux anyway we have implemented following behaviour.
1. By default the height of the housing is 0,1m or as height as the light emitting surface.
2. The user can override the default height with the correct height. The correct height can be e.g. looked up on the website of the manufacturer.

DIALux Partner can benefit from the ULD format which improves some weaknesses of other photometric formats. So if possible we recommend to provide the ULD file instead of IES or LDT files for easier planing and more accurate results. We are wondering that they did not support the ULD file even they are DIALux Partner.

Best regards
Fabian

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