Blender has come a very long way in just a few short years. One of Blender’s crowning achievements is the filmic view transform which provides a higher dynamic range of color data making for even more photorealistic renderings. However, there’s always been something not-so-dynamic about the filmic transform. This talk by Alex Fry can best describe why that is and how ACES represents a true(ish) dynamic range:
Of course, I couldn’t take others’ word for it. I had to perform my own tests, similar to those demonstrated by Fry.
I used a scene of metallic cans with a metallic label a spot light, a couple of area lights and a HDRI. Immediately, one can see the difference in gamma or light fall-off. In some areas of the scene, ACES crashes the blacks and clips the whites, like they would in reality. While filmic squashes all its information in the center of the histogram. The shadows never go black and there is no true white where there would realistically be clipped information. Yet, ACES preserves middle tonal range where they should exist. All indicators of a more dynamic range.
When I overexpose the scene by two stops and then underexpose it by two stops, you really start to see the difference in dynamic range. With ACES, lost information remains lost while the rest of the recorded data is pushed down or up range. Filmic begins to show its true mid-tone self. Check out the bottom left of the label to see what I’m getting at. The small white text in the hot spot of the can. All that information should be lost or “white” when overexposed AND when reflecting direct light. With filmic, you have to push the whole scene up two stops before that hot spot starts to behave the way it should–but at that point, the whole scene is blown out. Even though both scenes are blown out, there’s more preserved data with ACES. When underexposed, that little bit of text starts to come through two stops under with ACES. Meaning, the data toward 255 has a greater range, even though it’s perceptually clipped. The same can’t be said about filmic.
There’s more dynamic range with ACES right out of the box. So what? Filmic can be changed with further edits in post?
It’s not just about more range, it’s how the data is translated. Since light is color, we see a more realistic diffusion and saturation of color with ACES. As luminance increases, so should the desaturation of color. In filmic, we don’t see that happening in a “real” way. We can make further edits, seen in these examples, but how the color model is transformed, just isn’t the same.
Filmic does exactly what its name suggests, it is filmic looking. It’s very mid-tonal and at times kind of flat. Though, I don’t want to beat up on filmic. It totally works in most situations. That said, if you’re going for photorealism that strives to be perceptually real, filmic is not going to transform luminance the way it should be represented.