16K HDRI - Worth it?

[ValeroStudio]

Is it really worth using a 16K wide HDRI for lighting? Seems like overkill, right? These are meant to be used for the reflections I assume?

[kenancakir]

As far as i know, 16k hdr is good for background but bad for lightning.. Because too many pixels produce too many light source.. Low and blurred hdr produces more natural lights to the scene.. But i am not an expert of course, just my thoughts..

[GD3DESIGN]

This would be worth doing some tests to compare different resolution's results for environment & reflections. In the old days you would blur a low res version of the hdri for GI, then set up the high-res in the reflection override slot for your final render.... But, I wanna say with all the improvements to vray over the last 5-6 years that you don't have to do this anymore.(I personally haven't done it in years, but I've moved from quality to speed/quantity of the past few years...) I'm not really sure if you need that high resolution anyway, if your final render is only going to be 4-8K, right? It may depend on whether you are doing some interior where you'll see high quality reflections up close, or doing far away exterior shots. The important thing is making sure you have all the exposure brackets in the hdri, which is what actually makes it a true high dynamic range image, rather than super-high resolution. I'm not saying all this is correct, more of me just thinking out loud along with you. Personally, I just throw whatever hdri Peter Guthrie sends me into the vray dome light and roll with it.(not even sure what resolution those things are...)

[GD3DESIGN]

Out of curiosity, I just opened a random PG Skies hdri in photoshop to check the res, this is from 0917 Dawn---->

[ValeroStudio]

I see websites like CG Source selling 16K HDRI files and I always wondered if it's worth the memory and load time just for the lighting. The Tex. Resolution setting only have a max of 2048 for importance sampling? Does this mean no matter what, it's only using 2K resolution?

I ran a test a CG Source HDRI that I bought using 4K, 8K and 16K files rendered at 4K on High and see no discernible difference in the lighting. Render times were the same as well.

[GD3DESIGN]

Interesting. Maybe it makes more of a difference in Max where textures can be greater than 2K..? After posting the other night, I checked out PGSkies to see if he had any new hdri’s and noticed his new ones are in 14K, too. Must be important somewhere. I’m currently on vacation down in Mex, so can’t do any experiments of my own at the moment.

[caecarvalho]

I’ ve found that using 16k+ hdr/exr images, gives me nice and sharp background image and reflections if I’m rendering in 4k. You have to think that a 16k hdr/exr will be applyed to your scene all around your sky hemisfere, meaning it will be wrapped around a semi sphere in 360 degrees. So, when I’m rendering to a 4k output, I use at least a 16k hdr/exr image for nice and sharp background and reflections. Since vray has the dome light, you don’t have to use old methods like bluring a low res hdr for lighting and using the high res for background and reflections. You can use the same high res hdr/exr for everything, just by placing your high res hdr/ext in the dome light proper slot.
Personally, I like to use a low res vesion of an hdr/exr (no need to blur) in the vray dome light for illumination tests, since the resollution of the hdr/exr will not affect the lighting quality, but it will start the render much faster then using the high res version of the image. When I’m satisfied with the results, I then replace the low res with the high res hdr/exr and render my final image in 4k.
PS: there’s much more to a good hdr image than it’s resolution, when it comes to lighting. My favorites these days are from CG source, Peter Guthrie latest ones and Adam Martin’s 3d Collective (definitely my favorite).
PS2: Answering the post question, it’s worth if your using them for background, and reflections for high res render outputs like 4k and highier! As I said, if lighting quality is your only concern, resolution is not the most important thing.

Hope my insights can help!
Best regards,

Caetano

[ValeroStudio]

I very much like CG Source as well and this is what prompted me to ask about the resolutions. Thanks for the response, Adam's stuff looks very interesting.

[kenancakir]

I made a test and blurred hdr caused a little softer shadows but it is not a noticible difference, so i withdraw my first comment about lightning part..

[konstantin_chaos]

I’ ve found that using 16k+ hdr/exr images, gives me nice and sharp background image and reflections if I’m rendering in 4k....

This is exactly right.
If the HDR is visible in the background, then a high resolution map is preferable.
Sharp reflections can also capture environment details and are another reason to go high-res.
The lighting evaluation that V-Ray does is optimized internally so high resolutions should not affect render times significantly.
The texture loading time(before the render starts) on the other hand is going to increase with the resolution.