VRay Sun/Sky vs. HDRI

[grantwarwick]

It's a bit of a tough one alright. What you've got to do is have a few measured values at black, grey and white (such as a macbeth chart) and then ideally another measured value for a brighter source in your scene. The first three are okay to do since you can buy a chart, photograph it when you're shooting your hdr's and then just use a colour picker back and forth to colour correct those values into place, what's slightly harder though is the brighter value. Any gamma curves you do on your images are going to affect the overbright values very heavily so ideally it'd be nice to have a known value well above 1.0 so you can pin things into place.

What's kind of tough is even trying to figure out the response curve of your camera and the conversion from raw files into tif files without the conversion software adding anything weird in an attempt to make the photo look better.

Those math bastards at ILM coded an automated tone mapper based on Macbeth charts. How come Disney releases so much cool stuff but not ILM

[joconnell]

Yeah a mate of mine was working in another company that did stuff for them on battleship - he's trying to reproduce it now. It's just making a colour matrix inside of nuke based on those known macbeth values so if you'd a programmer with decent knowledge of light or colour I reckon you could remake it.

[RockinAkin]

Correct me if I'm mistaken, but doesn't the macbeth chart alone only help in color balancing the exposures and removing any camera curve / etc?

Are we not still missing an accurate measurement of exactly what that grey / white swatch (and some even brighter value as you mentioned) means in terms of real world luminance? So how do you (or a place like ILM) go about accurately measuring these values?

[grantwarwick]

Correct me if I'm mistaken, but doesn't the macbeth chart alone only help in color balancing the exposures and removing any camera curve / etc?

Are we not still missing an accurate measurement of exactly what that grey / white swatch (and some even brighter value as you mentioned) means in terms of real world luminance? So how do you (or a place like ILM) go about accurately measuring these values?

I will ask a compositor mate of mine who just finished extensive work on the Hobbit. Pretty sure he's implemented similar workflows himself when he was at Fuel.