The Effects of Diffusion on the C300 Color Fringing Issue

The C300 is a fantastic camera; I wouldn’t have gotten one if it wasn’t. But like all cameras, it has its weaknesses. One minor one occurs when you blow out highlights. The edges can look sharp and aliased (sawtoothed), and can sometimes show green fringing. This is different from the chromatic aberration that’s present to some degree in all but the best lenses, but it remains to be seen if it’s entirely unrelated. I suspect it has something to do with the way the camera debayers its raw input (the sensor is 4k, in blocks of 1 red, 1 blue, and 2 green pixels, and it scales that down in-camera to achieve its fantastically sharp 1080p imaging), which means a firmware fix might not be out of the question. But until then, I’ve been experimenting with ways to ameliorate the issue. One of them being diffusion. My hypothesis is that adding a touch of diffusion, just enough to smooth out the hard edge, will get rid of the sawtoothing and green fringing. Let’s see how it works.

The filters in the test. Click to embiggen.

The lovely folks over at Rule were kind enough to let me try a few different filters for this test. Here we’ve got, from left to right, top to bottom:

Schneider Classic Soft 2, 1, 1/2
Tiffen Black Diffusion FX 1/2, 1/4
Tiffen Black Pro-Mist 2, 1, 1/2, 1/4, 1/8
Tiffen Ultra Con 1/2, 1/4, 1/8
Tiffen Lo Con 1/2, 1/8

(sidenote: ignore the ghosting of the ceiling lights. I had my UV screw-in filter installed so the matte box would have something to clamp to. This has no bearing on the test, and would not happen in a normal production.)

Okay, in the first frame, you can see the issue in the fluorescent light fixture above the exit sign in the middle of the ceiling, and the ceiling lights nearest the far green wall.

Bam. Put on the Classic Soft 1/2, and the aliasing is smoothed out significantly, and the green is almost entirely gone. The effect is fairly transparent on the showroom background, but you can still see it. I’d like to see how a Classic Soft 1/4 looks. Randall Einhorn, DP on “The Office,” always uses 1/4 or 1/2 Classic Soft HD on the actors, and I’m kind of on board.

Continuing on, Classic Soft 1 and 2 are way too much for normal use. Tiffen’s Black Diffusion FX at 1/4 and 1/2 are indistinguishable to my eye here, and offer the same smoothing and fringe reduction as the Classic Soft 1/2, but with less halation. The Black Pro-Mists really affect the whole image, so they’re unusable unless you want it to look like you’re using diffusion. The Ultra Cons and Lo Cons seem to help a little too, but again, they affect the whole scene. Useful to see the effects, though.

All in all, from this test alone, if I want to throw a filter on that’ll change the image as little as possible, but smooth out the edges of blown-out highlights, and reduce the green fringing issue, the Tiffen Black Diffusion FX at 1/2 or 1/4 is the winner here. That said, I really have to see what it does in all sorts of situations before I have it in front of my lens 24/7. As always, test, test, test!

Stay tuned for the same filters tested when pointing at my ugly mug!


2 thoughts on “The Effects of Diffusion on the C300 Color Fringing Issue

  1. Conny Fridh says:

    Thank for this test. I was just about To Try the same thing. Looking forward To see some more test. But mist if all à firmware update and fix of This from Canon.

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