Thought I’d start off with something general, yet technical. Gamma correction and linear workflow. This is going to be hard to hear ( if you don’t know what I’m talking about ) but you’ve been doing it wrong.

In the majority of 3d (and compositing) applications you render 1.0 gamma images by default. Some of the new ones like Modo corrects your renders to 2.2. Without correcting the raw 1.0 gamma image to 2.2 you end up with a darker than expected image.

So what do we do? We push up the intensities of our lights, resulting in blown out speculars and unrealistic falloff on our lights. That’s why many of us used to work around this by separating specular and diffuse lights, pushing up the ambient colour on our materials and rendering many separate passes to try and get a realistic result.

sponza model | left gamma 1.0 defaults | right gamma corrected to 2.2 | directional light for the sun, constant plane for the sky, final gather for bounced light rendered in mentalray xsi

In the second image you’ll notice there is more light in the shadow areas, giving the impression that the bounced light is traveling further and helping to illuminate the scene more. Obviously better than the left image.

Technical Explanation

Have a listen to the fxguide podcast on linear compositing (right click, save as), they do a much better job of explaining the reasons why gamma correction is off by default in most applications, and why you should switch it on.

But to summarize, when you do anything in post, compositing or 3d animation you want all your calculations to be on the raw data (gamma 1.0 linear), and correct the result for display (sRGB 2.2).

How to enable it in your software

Next I’ll show you how to apply linear workflow to various software packages.

Softimage XSI

To enable 2.2 gamma correction of your render viewport/region and shaderball/color inputs go to File > Preferences > Display > Color Management and tick the 4 boxes under Apply To… Be aware that behind the scenes you are still rendering the same you always have, this only applies a “correction filter” on screen.

Next you need to enable correction of texture images. This will remove the 2.2 gamma on images before using them to render, making them darker. If you don’t do this step your textures will appear too bright and washed out. Under Preferences > Rendering > Images tab change Color Profile to sRGB and check that Gamma is set to 2.2.

When you want to render out your scene you have a choice. Preferably you should render out the 1.0 gamma images in .exr format, leaving the Apply Display Gamma Correction UNTICKED.
Or if you want the comping workflow to be the same as before, tick the Apply Display Gamma Correction box in your Render Manager window. This will make your image sequence look the same as your render previews/regions, and you should be able to render out to whatever file format you prefer.

Houdini

In Houdini, Edit > Color Settings > Color Correction tick all the boxes and set Gamma to 2.2 and click Apply (and Save As Default if you wish)

Aftereffects

In Aftereffects go to File > Project Settings and change your Working Space to sRGB and tick Linearize Working Space. I prefer working in higher than 8bit when dealing with subtle gradients to avoid banding, but that is up to you.

Be aware that you might have to color correct your footage using the Effect > Utility > Color Profile Converter.

When rendering out remember to specify the output color profile to convert your linear result back into 2.2 or else it will look way too dark.  Add to render queue > Output module (where you choose your output file/compression format) > Color Management tab.

Coming soon: Maya (mental ray). In the mean time try out the gamma node in your shader network to correct incoming textures/colors and the mia_simple exposure node on your camera to correct your output.

References and links

sponza model by Marko Dabrovic – hdri.cgtechniques.com/~sponza/files/
fxguide podcast linear workflow – http://www.fxguide.com/fxpodcast.html