Best Way To Set Exposure & White Balance?

[leejk]

Hello,

I'm using 6.1 and auto exposure and auto white balance do not really work in my scene; in fact, it has been recorded as a bug. So, I am wondering what is the best way to set these using a neutral process that is not affected by personal preferences? I am wanting to get to baseline, and then perhaps tweak that to personal preference. My scene is using VRay Sun & Sky with cameras facing and facing away from the sun, so it seems one exposure setting will not work. I've seen a few tutorials on this, but they seem to only work with interior scenes.

[glorybound]

Set your camera and lights to real-world settings, and tweak like you would with a camera. Auto white balance in cameras is usually pretty reliable, and I am assuming so is V-Ray's. If your lights and cameras are correct, then you'll only need minor tweaks. Some I know render with a gray override and use V-Rays' auto settings for their camera and white balance.

[will_will]

if I remember correctly, auto exposure and auto white dependent on the Light cache of secondary GI engine

[^Lele^]

As pointed out, you have a few staples you can use:

*) Physically accurate light values. They will largely match real-life counterparts (IES or not.)
*) Physically accurate shaders. For example, the response of a mid-gray diffuse will always be the same, so you can use one such override material to gauge lighting intensities and colors of your scene.
*) Physically accurate cameras. If you set the scene up with the above done right, the camera will return an exposure analogous to that of a real world one.
*) Scene units too play a big role: ensure you are to the right scale, so you don't accidentally emit 100 times more light than wanted (if the scale is 10 times bigger than expected, for example.).


EDIT: your baseline is anyways given by the auto-exposure.
That gets transferred to scene, and then tweaked as one pleases.
Would you be so kind and let me know of the support ticket number you were given?

[leejk]

Thanks guys for the responses. Using the gray override trick to set auto exposure seems to be the right method for me. In other tutorials I had seen them use near white, and adjusting exposure to match the actual RGB of the material, but they were doing an interior. With an exterior scene that produced a darker exposure that is too dark I found. I don't know anything about photography so that complicated it a bit because I don't know the steps involved with that but understand the exposure and white balance functions.

I used auto exposure and auto white balance with the gray override material and then transferred that to each VRay camera. In my scene, I still needed more ambient light, so I adjusted the VRay Sun multiplier to 2. I could have used a dome light to increase ambient, but that lightened up the shadows too much I thought. That produced a pretty good-looking render. Each camera now has slightly different exposure settings. Does my workflow sound right?

Before I was trying to control the ambient lighting with the exposure setting, and that I think was wrong, so was trying to figure out the correct "baseline" to start with.

@Lele: I think I am using real world scale and values for everything... pretty much starting with defaults on settings. I don't have the bug number, but my support ticket was 71589. Using the gray override trick mostly works except for in some camera views I still get a blue tint on the scene where it should not be when using auto white balance. Without the gray override the blue tint appears in all views.