In the second part of the mini-flow we’re looking at noise, specifically two “kinds”, how they affect your image and what to do about them before you hit the third leg of the mini-flow. Although it’s quite subjective, we feel that noise can be your friend… if you’re nice to it.
Enter the Denoise Plug-in.The two kinds of noise that we’re trying to understand here are Luma Noise or Luminance Noise and Chroma Noise or Chrominance Noise. Together, they create specific patterns that may or may not be pleasing to the eye. For a very detailed example you can visit the cambridge in colour tutorial here, this explained it to me years ago and I came to realize that I’m not afraid of noise as a whole, I just don’t like chroma noise.
I suspect that a lot of people may be more offended by the presence of chroma noise, which tends to look more “digital” versus the presence of luma noise, which looks more like “film grain”.
The issue is finding a way to tear both the abundance of noise and the chroma artifacts out while preserving the image detail.
Do it in post
[*****Critical Note: At the time of writing this, Magic Bullet's Denoiser is no longer available for sale. You can check the press release here: http://www.redgiantsoftware.com/blog/2011/12/01/why-will-denoiser-be-temporarily-removed/ -- I hope a new version is released in the near future, as the FCP Plug-in is quite buggy and crashes my FCP constantly. Read on...*****]
Although there are several types of denoising programs and plug-ins, I’m focusing on Red Giant’s DENOISER II due to the fact that it’s what I have access too and I’ve already figured out a how to get exactly what I want. If you have other Denoisers and you can replicate this process, feel free to send a message over. I’d like to incorporate it into the workflow.
Here’s the image we’re going to be dealing with. I chose this one because, well, everything looks great in daylight. The true tests, to me, are when we get into night or lowlit material.
(at any point, you can click the images to access the .PNG files)
And here’s a blow up of the noise pattern:
Drastic. Plastic. Unpleasant. I am not a fan.
Time to modify a few things. Take a look at the Denoiser II Panel’s default settings and options:
- 1. NOISE REDUCTION: Not sure why the slider’s designed like this, but 100 = 0 noise reduction. Below that does nothing, increments above that begin to reduce noise in various ways depending on the subsequent settings.
- 2. MOTION ESTIMATION: Calculates frame by frame to discern between what’s an artifact of motion (blurring) and actual noise. It defaults to low here.
- 3. ENHANCEMENT: Seems to behave like a somewhat more refined and compacted (one slider) version of Unsharp Mask. Note, that when using this without noise reduction you’re basically just sharpening the noise.
- 4. SAMPLE CURRENT FRAME: Denoiser needs a frame to pick its noise sample from. Ideally the right kind of frame would feature a grey card or a color card that represents the noisiest channel (my thought is the Red channel for GH2 footage, but I have not experimented yet.)
- 5. FINE TUNING: Drop Down Menu
- A. LUMA OFFSET: Deals with the Luminance Noise in an image. Higher the slider, the more it removes luma noise.
- B. CHROMA OFFSET: Deals with the Chroma Noise in an image. Higher the slider, the more it removes chroma noise.
- C. CHROMA SMOOTH: Sort of like a definition of how many pixels around the chroma noise to blur. Not very useful to me, but I believe you could get certain looks out of it.
- 6. ADVANCED SETTINGS: Drop Down Menu
- A. FOOTAGE SOURCE: Video or Film. Self Explanatory.
- B. NOISE HINT: Gives denoiser an idea of how much noise is in the image.
- C. SHOW NOISE DETECT: Only works with FILM
- D. NOISE DISCRIMINATION: sets a bias between how much noise is retained or loss, also for FILM.
- E. SHADOW OFFSET: Tells Denoiser to increase or decrease the amount of denoising going on in Mids and Lows (shadows)
- F. HIGHLIGHT OFFSET: Tells Denoiser to increase or decrease the amount of denoising going on in Mid-highs and highlights.
7. MIX: Slider to mix on keyframes.
Specific to this, we’re not dealing with any of the Advanced Settings, but they do work and you should try them out to see what you get. Particularly, by re-balancing the Shadow Offset and Highlight Offset you’re able to dial in your preference of noise in either areas.
Here’s what my settings look like for the typical occasion, which means I try to run everything (daylit as well) through this:
And here’s the blow-up:
You can click this and the earlier two hundred percent blow-ups to A and B the frames
The differences may be more subtle here than in other examples, as this image is balanced well, but you can definitely see how the “conversion” of Chroma Noise to Luminance Noise is affecting the image.
When I say conversion I’m referring to the fact that the noise is still present, but now it’s closer to a colorless noise or white noise.
To my eyes, the severe decrease in chroma noise pushes the image to a completely different level. Also, keep in mind that a sequence of frames will also be the final tell of how the noise reduction changes things. Mileage may vary depending on tastes of course, so make sure to experiment for yourself.
Here’s another example of Denoiser with a slightly more liberal approach:
And then blown up:
Noise is still present but becomes very mild in appearance.
At 160, I’m just over the edge of sacrificing high frequency detail, like creases in skin; say the wrists for example. My thought is that somewhere between 130 and 150 could be a great balance for those who like clean images but still want to retain as much detail as possible.
When’s the best time to Denoise?
My personal belief is that you’d want to denoise right before you go to a final grade. It doesn’t make much sense to grade with a ton of chroma noise in your footage, you would be effectively judging your final color work on the chroma noise you’re also grading.
Once you rip the chroma noise out, you’re left with what may be small to large chroma shifts depending on the severity of the noise. Here are some subtler examples:
Chroma Convert | Color
160 Reduction | 60 Enhance | Color
There will always be other workflows and methods
So experiment, try out your own, see what works best for you. Just by doing this blog entry I learned that I actually could apply more of a denoise altogether and I would be fine with the results, whereas before I was very apprehensive to do anything more than converting the chroma to luma.
That also showed me that I could be much happier with ETC mode, because if you hadn’t realized yet… yes, these are images from the GH2′s ETC mode at around 800 ISO, which is nearly 2 stops noisier than non-ETC mode.
Shoot it up!