Vray lights in newest build

[tricky]

The readme says:
Accurate light emission units (lumens, watts etc). For best results, use this feature with the V-Ray physical camera.

We had been using RC3 on Max8, but have just installed the lates 1.5.00 build. Does the above statment mean that putting in a 60W vray light is now more like a 'real' 60W bulb? I am pretty that on RC3 even low values of 0.5W used to give a lot more light (something to do with 'actual' W values rather than manufacturer 'stated' values IIRC)

[vlado]

It means that a 1700 lm VRayLight will emit the same as a 1700 lm Photometric 3ds Max light.

Do not use Watts to specify the power of your lights; use lumens instead. The reason being, that, in V-Ray, the light intensity refers to the visible light power, whereas the "60W" in a 60W-light bulb refers to the electric power that it consumes (which is a whole lot more than what the bulb actually emits back as light).

Also, when you use photometric lights, it makes sense to use a VRayPhysicalCamera with the correct exposure parameters for the scene that you are rendering.

Best regrds,
Vlado

[tricky]

Thanks V - looks like I need to 're-learn' bulb intensities as I have a 'feel' for how bright a 60W bulb should be.

[vlado]

Most manufacturers usually provide the lumens emitted by the bulb on its packaging. I know that a 100W bulb typically emits about 1700 lm.

Best regards,
Vlado

[tricky]

OK, thanks.

[travistlo]

http://en.wikipedia.org/wiki/Incandescent_light_bulb

If you scroll down to the Luminous efficacy and efficiency section it shows the general Lum/Watt for each type of light.

Pretty useful if you know that is a 100w incand. or a 200 watt halogen.


this one has a bit more info.

http://en.wikipedia.org/wiki/Luminous_efficacy

[tricky]

Ta very much lad.

[DaForce]

Using Watts is abit like refering to the power of an engine by its engine size. 4L for example.
Lumens its like referering to the power the engine produces 300kw/hp.

For example a 60w bulb only produces about 7w of light power?? (something really low) the rest is mostly in heat.

[WWX]

Ask this question, but its seems to have flow under the radar, so I hope you don't mind me adding it here as i think it is related to your topic.

Using lumens as your light intesity setting, does it still mean that 1700lumens will only be represented correctly if both the unit settings in max are set to meters?

Thanks

[vlado]

Using lumens as your light intesity setting, does it still mean that 1700lumens will only be represented correctly if both the unit settings in max are set to meters?

It doesn't matter what units you use, but that your scene is correctly modeled to these units. For example, it doesn't matter if you use meters or centimeters or millimeters for your scene units, so long as in all cases your room is e.g. 6 by 4 meters or 600 by 400 centimeters, or 6000 by 4000 millimeters.

Best regards,
Vlado

[WWX]

Great! Thanks

[tricky]

Must remember to tell my wife the next time she goes to Sainsburys to pick me up a 1700 lumen bulb for our standard lamp in the living room

[Dynedain]

Must remember to tell my wife the next time she goes to Sainsburys to pick me up a 1700 lumen bulb for our standard lamp in the living room

The reason why all fixtures are rated for a certain wattage of bulb, is because they are referring to electrical watts as a measurement of how much current you can safely pull through the wiring, not a measurement of a bulb's intensity.

You can put an 60 watt incandescent or 60 watt compact flourescent in the same fixture and both will draw the same amount of electricity (60 watts), but the compact flourescent will output incredibly more lumens.

[andrewjohn81]

if only we could change the intensity of the shadows, not just on/off