Adjusting Floating Point Images

[JamesTaylor]

I'm just starting to bring Floating point images into my work flow and want to make sure i'm working with them correctly, as well get the concept sorted in my mind!

 

I'm wondering what the procedure is if i want to adjust the brightness / contrast in a floating point image using photoshop (or after effects)?? do i still simply use the adjust contrat and brightness tool or do i use levels or doesn't it matter??

 

Or...is it simply the fact that whatever adjustments i make are being applied to an image thats highest and lowest values haven't been clamped inorder to keep them within the limits of an 8 bit colour range?? as such the adjustments are being applied in a uniform fashion??

 

Is there predefined values or a way to work out the adjustments required to move the image between f-stop values or simulate the use of different ISO values when used in conjunction with VRay sun sky and physical cam??

 

any pointers or links much appreciated

 

Thanks

 

James

[LuckyST]

I'm also interested to know more on the subject

[aaronrumple]

Get it right when rendering so you don't have to do much adjustment.

 

I work my exposure for exteriors with vray for as "real camera" as possible. Then there is little to no adjustment when moving over to photoshop. At the most I might adjust the shadow level a couple for percent.

 

For interiors I expose for the interior once again trying to get the color/lighting/exposure right first. Then I run the image through picturenaut to tone map any windows that have burned out. I've tried other systems (including PS) but get the best and most predicable results with picturenaut. The less I have to adjust the better.

 

Just like real photography, the darkroom (PS) is not the place to be adjusting exposure to make up for bad photography.

 

In all cases, I use linear color mapping with LWF and a 2,2 gamma.

 

The fastest way to adjust exposure in vray is do a quick test that is in the ballpark. Then use the frame buffer to adjust the exposure. Once I know what the over/under setting is from this tool, I'll apply that to the camera and turn off the exposure control. Usually one or two tests is all it takes.

 

Attached is one that is in progress where there was no adjustment from vray to photoshop.

Edited December 21, 2009 by aaronrumple

[LuckyST]

cool glass reflection you have going on there...

whats the trick? falloff maps or smth. else?

[aaronrumple]

Just a simple Vray glass.

Diffuse=0

Reflect=243

Refract=243

Fresnel=1.6

Fog is 0.5 w/ 0-199-108 for a little green tint. Select color as appropriate for design.

 

Then you just need to give it things to reflect. I like the new vray CIE sky better than the old system. Also there is a big cylindrical map of a tree line all around the scene (running around behind the camera.) There are some minor model items inside the building such as walls and stairs to add interest when the glass looks more transparent.

[LuckyST]

thanks. I've completely stopped using fog, since it used to create problems for me back in the old days, that I sort of forgot to use it in a while

 

thanks