The Visual Difference Between Linear and
Non Linear Workflow
By Neil Blevins
Created On: Sept 21st 2013
If you don't know a lot about Linear Workflow (LWF) yet, you may wish
Wynen's Linear Workflow tutorial and my Linear
Workflow In Vray For 3dsmax Cheetsheet before reading below. While
these are max/vray specific tutorials, the theory is the same for all
renderers and 3d apps.
This lesson comes out of a discussion we had on the vray
forum, there's plenty of tutorials discussing how to use Linear
Workflow, and why you should use
Linear Workflow, but there isn't as much information out there on
exactly what the visual difference is between a Linear and a Non
Linear workflow image. Lets take a deeper look at exactly what
The following two images are made with a neutralized lighting rig. That
means that if you provide a material that's 50% grey, the end result in
your render is 50% grey. The Non Linear image has a input color of
128,128,128 and the Linear image has the same color but with a gamma of
2.2, in order to achieve the same final color in the two renders (this
is discussed in more detail in my Linear
Workflow In Vray For 3dsmax Cheetsheet). This way, we can compare
apples to apples.
has a single area light from the upper right, no sky or fill light and
Feel free to save the images and flip between them to see the
difference more clearly.
You'll see the main difference is that the Non Linear one has a much
softer and gradual falloff to black, and the Linear Workflow
image has a
larger area of flat bright color and a sharper falloff to black.
Alfa Smyrna on the vray forum I think said it best: "I see LWF as
the falloff curve for the transition from black to white. I perceive it
as a falloff for greys so gamma=1 is a more steep transition but
especially for interiors with small openings, LWF makes the greys look
more similar to real life distribution of light."
My renders above support that idea, the two workflows have a very
different falloff curve for the transition from black to white.
Here's another example, this time something more complicated. The
linear workflow image has less contrast than the
non linear workflow image...
In this example, I apply a levels in photoshop to the Linear Workflow
image and get back an image
that's a lot closer to the Non Linear image.
Here's a similar example, but this time with texture maps...
Similar results, although the Linear image run through the Levels Color
Correction is not as close to the Non Linear render because the levels
color correction is adding contrast to both the lighting of the scene
as well as the textures.
Here's a more complex lighting situation, a skylight using an hdr image
map with a number of GI bounces (the ground surface is 50% grey at the
material level and in the final render)...
This is a great example of the downsides of not using Linear Workflow,
the image on the left has plenty of contrast, but notice that the
and the texture map I'm using look like this in photoshop...
So the texture maps in the left render are way too dark. With Linear
Workflow, the texture maps look a lot closer to the real
colors, but the lighting is less contrasty.
BTW, here's me applying a Curves color correction in photoshop to the
It's not as contrasty as the non linear image, but has deeper blacks
than the linear image.
Now, whether you like the more contrasty image or the less contrasty
image is a matter of taste, it's an artistic choice. Mathematically,
Linear Work Flow is better for a number of reasons, and it's easier to
integrate cg elements
into real photography using Linear Workflow. But artistically, you may
be after something different. Afterall, realism may not be your goal.
Even in live action films the Directors Of Photography will shoot on a
film stock that specifically
increases contrast, or will crush the blacks at the color grading step.
If you like the final look of the linear workflow image, then great,
you're all done. But if you want to get your contrast back, here's your
What your choose is up to you, but hopefully this lesson will give you
a better understanding of the problem, which hopefully will lead to a
solution that works better for you.
- Don't use linear workflow. You'll keep your contrast, but your
texture maps will tend to look wrong and you'll have to do a lot of
extra steps since almost all renderers and 3d apps now default to
linear workflow. Also, you may get incorrect results with displacement
maps, for example, if you export a displacement map out of mudbox to
use inside 3dsmax, you want to set its gamma to 1, or else you'll get
incorrect results, since you want the absolute numeric value of the
map, not a visual value.
- Use Linear Workflow, get contrast by color correction. So take
your LWF image and bring it into photoshop or a compositor like Nuke or
Digital Fusion, and use color correction to increase the contrast of
your image to your liking. Some common tools would be Levels, Curves,
gamma, exposure, etc. Also, you may want to save your image out of the
renderer as a floating point exr with a gamma of 1 since that'll
provide you more data to do your color correction on, and then the last
step is applying the 2.2 gamma in your composite.
- Use Linear Workflow, adjust your lights. In more complex
situations, you can get some of your contrast back by reducing the fill
light in your scene and/or reducing the multiplier on your secondary
light bounces (if using GI)
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