ies file seems to be much dimmer than it should be. Despite accurate camera settings and default dome light

[zach_ryder]

Hi all,

For some reason my ies lights seem to be too dim when I leave the default (lm) value. The ies lights are from a popular website and I've tried may different ones. My best guess is that it might be because the vray dome +sky method is brighter then real would natural lighting conditions but I'm unsure. I'd like to make sure I'm using the most accurate lighting for my recessed lights. Ill attach a photo with the recess lights turned on and one with them turned off.

Thanks in advance for the feed back!

[natalia.gruzdova]

Hello zach_ryder,
Thank you for your interesting post!

First I wanted to reference the documentation page for IES lights and point out that the intensity values of IES lights are provided by the manufacturer (just as you have noted).

Apart from that it is important to take into account several factors:

• Camera exposure. You can check out this diagram as a starting point for Exposure Values to match your lighting conditions.
• Overall illumination (indirect and direct illumination).
• Materials color and properties (i.e. darker colors absorb light).
• Display properties and intensity.

V-Ray works much like a real-world lighting tool and camera. Because of that your lights might appear powerful in a scene where the camera exposure is high and dim in other scenes where the camera exposure is lower. If for example a lamp is used in a nighttime setup where the camera exposure is high it might look nice and bright. The same light rendered outside on a bright sunny day will hardly be visible. It is entirely up to the user to make sure the lighting in the project is balanced.

To test the intensity of the IES you can do the following:

• Disable all the lights in the scene (including Sunlight and Background in the Environment slot).
• More importantly disable Exposure, so No Exposure is used for the test.

Here is an example video of such test. Apart from that there are free IES viewer tools you can find on the internet to check the intensity if needed.

In case with your scene you can also try to disable Exposure and Dome Light. You may adjust the Exposure afterwards to match the result you get with No Exposure. If the intensity of the IES you use is too low for your needs please consider searching for a different IES profile with higher intensity.

Alternatively you can use Light Mix render element to further adjust all your lighting once the image is rendered (for easier use set it to Group Instances).

Hope it helps.

[zach_ryder]

Thank you for helping me out! So i am familiar with exposer and making sure everything looks right and have even tested it in a with no envirment lights on. But even when I replace the ies lights with vray spot lights with the same lumens valuje, they are much brighter. Is this because the shape of the cone is different or something?

Thank you!

[natalia.gruzdova]

Can you please attach any of your IES files you are comparing with? Thanks in advance.

[zach_ryder]

I just tried to attqach the ies file but it wouldn't attach. I got it from ieslibrary.com under the recess section. It's a 4" 3000K recessed light ies file

[natalia.gruzdova]

Hello zach_ryder, I apologize for the late reply. Thanks for the website link.
I have tested comparing several IES set to 1000 lm with default Spotlight also set to 1000 lm intensity.

I would say that intensity is generally the same but you are correct that the light distribution is dependent on the shape of the lights.

I am attaching my test scene (V-Ray 6.10.00 SketchUp 2022) and the render result:

I just tried to attqach the ies file but it wouldn't attach

You can attach it by creating an archive with .zip extension for example.

[zach_ryder]

Thank you so much this is very helpful! I guess the light shape is whats throwing me off but this makes since

[natalia.gruzdova]

I am glad it was helpful! Do not hesitate to post on forum or contact us in ticket should you have any question!