vrayies lights sometimes just don't seem bright enough

[tricky]

I'm experimenting with vrayies lights on a project as I have been given a lighting spec: I thought as the IES data was available, I'd give it a try.

The lights in question are by the manufacturer 'Concord', and here's a link to the ies file www.blinkimage.com/downloads/Torus%20100%20FX%2034%20deg%20flood.ies

Each light apparently is equivalent to 110W (950 lumens). I have 2 tracks of these lights running along a ceiling, and there are about 30 lights in this particular space. A number of these lights are around 2m from the nearest wall and are pointed at the wall.

I find that I barely get any illumination from the lights without whacking up the default lumens output massively (5 or 10x the default 950).

The camera is a vrayphysical camera, f:4, 1/50th second at ISO:100.

Is this odd, or expected? To my mind, shining a 100W (or 50W) bulb at a wall 2m away would at least create a spot of light on that wall, even in a reasonably well lit space.

[pskdude]

yes, I remember reading some threads some time back the the multiplier had to be bumped up in some instances I have to do it myself. I find it odd as well.

[glorybound]

Ies

I find this odd, too! I get lighting data from our lighting engineers, but it almost doesn't mean anything because the real world data that they give you doesn't work. When I get these files I have to crank things up so much that I am really just guessing so the science is lost.

[tricky]

Does everybody find this then? It would have been nice to base imagery on reality and real values (within reason of course!) sometimes.

[psa]

I am having problems with VRay IES and 3ds max photometric lights too. I work in LWF and with regards to camera settings everything seems to be working as the realworld counterpart. All my camera settings, both for exteriors and interiors, matches pretty much the setting I find when using my DSLR. But when it comes to IES lights I have to use some extreme luminance values, which makes it impossible to know what light you need to use in real life to get a specific effect. (Its also bad seen from a Global Warming point-of-view, hmm). Is there a connection between the system unit scale and how the IES light data is interpreted? It would be nice with a comment from Vlado on this subject.

regards

[psa]

Here are a link to another thread about the same subject: http://www.chaosgroup.com/forums/vbu...hlight=VRayIES
Unfortunately I am still wondering why IES files doesn't work with my LWF, or how to figure out how to scale the light if needed.

regards

[prey1979]

I have always had problems with IES lights within vRay..
my models are coming from inside revit wich exports the FBX file as Feet and INches...

i have my system unit scale set for feet and inches...

however the ies files even with physical camera dont seem to work... its very frustrating.

[vlado]

Do they work fine with other renderers (e.g. the scanline renderer, or mr)?

Best regards,
Vlado

[Deflaminis]

I've found this to be true as well. And to answer you Vlado, they do work fine with mr. Even more weird is I've found that IES lights have very odd shadows from Vray, very crispy and no softening much of the time. I always figured I was just doing something wrong but the more I've experimented the more I feel that something is off.

I did have a thought about it though, in maya using a point light with IES data reveals 3 different methods for handling the profile. (The names escape me at the moment) I'm thinking that there are different light models for IES files as evidenced by the 3 options in maya for interpreting them. Maybe this is part of the problem, but I am totally guessing.

[vlado]

Ok; if you have a scene that renders differently in V-Ray and mr, can you send it to me at vlado@chaosgroup.com? We've gone through hundreds of IES files and they render consistently, but there might be something else in your scene.

There are indeed three different types of IES files, but there is no need to specify them explicitly - the type is written in the file itself (3ds Max does not allow you to change the type either).

Best regards,
Vlado

[tricky]

I've found this to be true as well. And to answer you Vlado, they do work fine with mr. Even more weird is I've found that IES lights have very odd shadows from Vray, very crispy and no softening much of the time. I always figured I was just doing something wrong but the more I've experimented the more I feel that something is off.

I did have a thought about it though, in maya using a point light with IES data reveals 3 different methods for handling the profile. (The names escape me at the moment) I'm thinking that there are different light models for IES files as evidenced by the 3 options in maya for interpreting them. Maybe this is part of the problem, but I am totally guessing.

Love your avatar. Max Headroom: I'd like to see that again!

[Deflaminis]

Ok; if you have a scene that renders differently in V-Ray and mr, can you send it to me at vlado@chaosgroup.com? We've gone through hundreds of IES files and they render consistently, but there might be something else in your scene.

There are indeed three different types of IES files, but there is no need to specify them explicitly - the type is written in the file itself (3ds Max does not allow you to change the type either).

Best regards,
Vlado

I'd be happy to Vlado, thank you for your time.

Love your avatar. Max Headroom: I'd like to see that again!

As a kid I swore that it was in 3D! Max headroom inspired me to become an artist and boy do I miss that show as well!

[psa]

I did a test last week with a scene I am currently working on. I did a render with both mr and vray - and they appeared to be nearly identical. But the strange thing is that while they looked right in a "night" setting, the light disappeared in the daytime version. I tried some different upscaling of the lumen settings and in this case a multiplier somewhere between 8 and 16 seemed to be what looked realistic. It is a little late now (after midnight), but I will try to post some of the renderings tomorrow.

To Deflaminis: did you check "use light shape" to get soft shadows. If you don't you will get sharp shadows.

To Vlado: thank you for the response, I am sorry that I didn't react on your answer until now.

Best regards,

[psa]

Here are some of the test renderings I made, as mentioned above. Please read my post for details. Some additional information though: I am working in linear workflow, system units are cm and the camera settings are similar to real wold settings. EV means exposure value, so EV 5 equals a camera setting of for instance 1 sec. f5.6 ISO 100. Image 1 should represent a situation with no additional light sources, except for some exterior moonlight. Image 2 has the same light setting as image 1, but with the moon replaced with a sun. Image 3 and 4, with the power multiplied with 8 and 16 respectively, are the settings which are closest to how the lamps (Flos Glo-Ball) behave as I recall from my memory. A multiplier of 10-12 might actually be the closest.



To sum it up, in this case the interior setting at night seems to be ok, but the settings in daytime have to be multiplied in some way to look right.



Best regards,

[davision]

The exposure is being changed from .5 to 1/128 second. It's expected for the lights to become much dimmer, isn't it? That's a much faster shutter speed. Set your lights to 256 multiplier and they should look the same. That's 8 f-stops worth if I'm not mistaken.