Daily Blender Tip 364: Lumens Values in Lights
Jan van den Hemel writes:
Some architectural plans will list the light values of the lamps used in Lumens. Unfortunately that means you’ll have to convert those to Watt as that’s what Blender uses as it’s Power value for lights. How do you convert this, and how do you set the color temperature? Find out in this quick tip.
PS isnt that lm/w a bit high or is that normal for LED. I use a different software were we can input efficiency and its always around 16/20 as base.
Another thing which is kinda a weird related to blender. Normally in real lif the power of a lamp is also seen or noticed with the iso, shutterspeed and f-stop. But none of these are in Blender. So isnt it a bit weird to get proper lighting then?
The camera has F-stop and exposure
Blender still needs to set / agreed to a default for the representation of light intensity in the value’s of Lux and Lumens.
Like Dialux or Relux has done as well. It’s not a real representation of light intensity; but a suitable one to do the job right.
A good formula is needed to take different factors in to matter. A conversion from Watt’s/Square meter is easy. But to find a good relationship between the factors Lumens > Lux > Candela; all need to precisely interact within the Filmic color management to get a close to an accurate representation of the real world values.
Right now the representation is not accurate at all and confusing. Like; when using an IES file. It contains all of these data (Lumens > Lux > Candela), but still; after importing the IES file; none of the point light settings are adjusted correctly.
In fact, when you try to get as close to the representation of brightness of a program like Dialux; you’ll need to manually set the power to 1 Watt, size; also defined by IES file; would set it to 0 or the size of the armature etc.
Hope they fix this soon…
an IES file does will adjust light settings, it contains data how the light acts. So its shape. falloff, hotspot etc etc. It has no influence on the power, atleast most of them.
Indeed. I think that’s a downside in how Blender interpreters the data.
IES files from for example light manufacturers contains the things you mentioned, based on lumens and the candela which influences the shape, falloff, hotspot in lux (light in the target area).
Blender does not see these parameters as lumens, candela and lux. But should, in my opinion.
If Blender would have a default for the representation of light intensity; the parameters like falloff, beam, source size, hotspot etc. could be defined as more accurate values like lumens, candela and lux.
I think that would be possible at all, your basically changing the light profile. The IES mimics also how the light is cast by its housing. If you open it in an IES reader or online IES reader you will see that profile. That can be changed in a simple way. Not that I know of. You could change the numbers in a text editor however. You can see all data in those files