I have recently gotten my hands on a full-format camera (Sony A900) and have kicked my photography hobby up a notch. I’ve always shot jpegs but now i have started to going over to RAW-photography because i want to learn more about post-processing. So far i’m happy with the results altough my skills right now stretch to adjusting exposure compensation, saturation, contrast etc. I’m happy except for one thing, the noise.
My RAW images has a lot of noise even at relatively low ISO (300 and up). I’m using RawTherapee and have been playing with the “Luminance” and “Luminance Detail” sliders but i find it hard to get a perfect result. Is there a good tutorial on noise reduction? Do you have any tips on how to reduce the noise without losing to much detail and making the picture “fuzzy”? I’d happily recieve any tips on how to improve my noise handling skills.
PS. English is not my native language and i have no idea what many photography terms are called in english. Hope i made myself clear anyway.
On the fifth tab of tools, under ‘Sensor with Bayer Matrix’ → ‘Demosaicing’ is a dropdown box. By default it’s ‘amaze’ which is good for black and white detail, but which suffers from color noise and some color moire.
Change it to LMMSE, which inherently suppresses chroma noise and color moire better than amaze, although it has more mazing-type moire artifacts if you have extremely sharp lenses at wide apertures.
Other tips I have for reducing color noise are to use defringing (set it to do all colors, instead of a hue curve) instead of normal chroma noise reduction.
After you remove the chroma noise, the remaining luminance noise isn’t nearly as annoying…
@CarVac means to find the lmmse method here in RT:
There are two types of noise that we mainly see in images, Luminance and Chrominance. The luminance shows up as a sort of “salt and pepper” type of grainy noise, while the chrominance noise shows up as blue/red splotches and blooming.
Normally, just clearing up the chrominance noise can do wonders to drastically improve the perception of noise in an image (as @CarVac already mentioned).
The thing is, for many photographers with a film background, we often prefer some sort of grain structure in the image, and luminance noise is similar in appearance to this - so we don’t mind it as much. I’m wondering if @Morgan_Hardwood would agree…
I’ve been applying the lmmse to a few images and love the result. As you both say, the noise is not at all as obstructive when you remove the chrominance and i can appreciate the aestetics of the “black and white” grains.
Right now all the sliders and menus are really overwhelming. I have no idea what 90% of it is, it’s mostly weird names. But now i have one of them understood at least.
The other benefit to lmmse is that when you have noise in amaze or the standard demosaicing methods, individual bright pixels much more strongly affect the luminance of adjacent pixels.
In LMMSE, a bright, uncorrelated pixel that stands out too much will have its luminance also be more independent of the surroundings. This leaves behind easy pickings for the impulse denoise tool which attacks individual bright pixels better than the little two and three pixel groups left by amaze.
Awesome! Glad you’re making some headway with it. I promise it will get easier the more you play with it…
They’re mostly weird names to most of us until we bother to learn more about them. In the meantime, push/pull sliders and see what they do! I still do this…
Overall I prefer the output of LMMSE to amaze because of the reduction in chroma noise.
It seems to give at least a stop or two of bonus high iso capabilities, and it also likewise extends the low iso dynamic range by the same amount (though that’s limited by color accuracy at some point).
And anywhere the maze artifacts show up, amaze has color artifacts that are more visible, so it’s not particularly worse in any areas, except some issues with highlight recovery in libraw that I think may be caused by off by one errors.
That’s why it’s my own editor’s default algorithm. (Also because it’s got a paper explaining how it works while amaze is just illegible C.)
The crazy number of tools that appear to all do the same thing is one of my biggest issues with RawTherapee. There’s no guide explaining what each one does in context of the others, so it takes a lot of experimentation. And some I consider useless, superceded by newer tools, so I don’t know how they could clean it up to make it easier for new users to jump in.
I’m writing my own program that is focused on having the fewest number of redundant tools, and on having detailed tooltips that explain how to use each tool in relation to the others, but I have yet to actually get feedback from anyone who I don’t know in person… I don’t know if anyone else is actually trying it.
I’d love to try it if i was a bit more experienced. Not sure my feedback would be of any help. Sounds interesting though, would love to try it out once you’re done with it.
I/we can do a blog post about your program to see if we can get any volunteers to try things out and provide feedback (assuming it’s F/OSS). You can also start a new thread here to try and get some extra visibility and feedback. (I understand how important having feedback can be - there were many wonderful folks who put up with me as I was building this site out).
Maybe I’ll try making a post on the forums first, then maybe a series of blog posts about the different aspects.
I probably should also add the ability to import photos without moving them before really advertising it, since right now it has to copy them to a new folder structure to be able to process anything.
I generally don’t take part in discussions when the original raw file and a screenshot of the problem were not provided, but I can make some general statements.
@GuyFromTheSky the starting point for help with RawTherapee is RawPedia: http://rawpedia.rawtherapee.com/
The article for the Noise Reduction page is not completely up to date with the latest version but despite this the information is valid and explains how to get optimum parameters. Chroma noise reduction is automated in recent RawTherapee versions. I will update the article when I have time.
Feel free to ask me anything, but first make sure you’ve read the relevant RawPedia page(s).
Do you live near Helsingborg?
I fully agree with what was written above, specifically:
with using LMMSE on noisy photos; that is the default in RawTherapee’s “Default ISO Medium” and “Default ISO High” profiles.
with using chroma noise reduction (automatic in recent RT versions) without using luminance noise reduction, as the result reminds one of film and is generally pleasing.
There’s no guide explaining what each one does in context of the others, so it takes a lot of experimentation. And some I consider useless, superceded by newer tools, so I don’t know how they could clean it up to make it easier for new users to jump in.
RawPedia explains everything. Each tool is covered individually; their combined effect is not special in any way. If something is missing, please ask and I (we) will try and document it.
This is an excellent read, I started using RAW as my default setting in the summer of 2014 (when I started a little project of 50 mono portraits with my 50mm lens). RT is my Raw editor of choice and GIMP for finer adjustments. I was surprised when I started seeing noise on my output jpeg’s.
Somebody told me it was because I was adding a little bit of sharpening on all my images (something I tended to do by default in GIMP, as a friend told me it would always add a bit of oomph to any shot). So I stopped sharpening, but still sometimes see noise.
I then thought it may be because a lot of my street portraits were on an old Canon 450D at ISO 400 and was blaming the old equipment ! I don’t know why though because the old 450D has given me some cracking shots
To reduce noise I was just indiscriminately moving my Luminance Noise Reduction sliders around until any noise vanished.
This thread explains quite a lot and I will try some of the techniques described.
At the moment reducing the noise is the last RT action I do (other than a crop).
Given I like to produce monochrome images, should I be doing the
noise reduction on the colour image or the final mono image? Having
read the thread I would say on the colour
Having said that at what point in the PP do you recommend reducing
noise? My workflow is find a bundled profile or personal profile I
like (or not like, in which case I start at neutral) and then work my
way down the editing tabs and across the tabs.
I really like the mono film emulations and tend to use these for a choice of mono.
I think I have rambled on a bit. Thanks for listening
Were you not seeing any noise previously? That is, are you saying you see noise now after doing raw processing vs. jpg straight out of the camera?
If so, I’d say that the camera usually applies noise reduction to in-camera processed jpgs, while your raw data is exactly that - not touched at all.
Generally, sharpening will work indiscriminately across the image, meaning if there was some noise there, a sharpening process will likely sharpen/enhance the noise as well. (Believe me, we all fight this balance of noise/sharpening to some degree… ).
This is a start. Now the trick is to fix the indiscriminately part to targeted adjustments focused on a result. That is, experiment with the how and why until you get a feeling for it to best understand what will happen on future images. (Then pay it forward and come back to write an article about it… ).
The pixel pipeline in RawTherapee is fixed, meaning that the order of operations that get applied to the image is not something you control. If you tweak a bunch of parameters, then go back and modify noise reduction, the image gets re-processed with the NR being applied when it needs to be.
A good path forward would be to find an image of yours that you like, and focus on two main areas while you learn the parameters and controls a bit:
One would be a solid color area possibly with gradients, like a plain wall with light falling across it. This is to help distinguish the chroma noise from luma noise, and how you can adjust parameters to reduce it to your liking.
Two would be an area in the same image that has some fine details. Hair, weave of cloth, facial pores, anything with fine details in it. The reason is to see how too aggressively pushing NR in one direction may smear or destroy those details.
Then the game is a balance between those worlds. With the referee being your personal vision and taste. This process is handy, I think, because it doesn’t assume anything about the methods of NR, only a look at some broad areas that will be effected that you can tweak to suit your tastes…
I generally don’t offer advice unless a raw image + sidecar file + screenshots or sample output files are provided, uploaded to http://filebin.net/
I can answer your questions:
The order of tools in RawTherapee is hard-coded, they all lie in a “pipeline”, so e.g. changes to the White Balance tool will always happen before the Noise Reduction tool, unless we the developers change that.
Knowing 1, the question becomes “When should I use which tool?”
Basically start with global adjustments and work your way down to detail adjustments. Start with the Raw tab, though generally you don’t need to change anything there. Then set the correct white balance, then use the Exposure tool, then whatever else in the Exposure and Color tabs, perhaps then the Wavelet tab, and end with the Details tab.
If the tool order is hard-coded then why did I just write that? For two reasons:
Changing some tool can “break” the carefully-adjusted result of some other tool, e.g. a strong white balance change might require an exposure or highlight compression change, or adding a flat-field in the Raw tab after you’ve adjusted exposure settings will likely require you to re-adjust the exposure settings, and changing exposure may require you to re-adjust the Color-toning tool.
Some tools are computationally intensive so it’s best to turn them on last. Luckily Ingo optimized the hell out of them so now they’re much faster, and furthermore these tools, such as Noise Reduction, are only calculated when you zoom to 100% so you should incur no speed penalty having them enabled while you’re zoomed out.
If this is a sensible or reasonable workflow to work through processing an image would it make sense to move the tabs around in the editor, or allow for the tab order to be made user settable (and this is a dangerous question as I’ll admit I haven’t tried to check if it isn’t already a configurable setting).
Hey @plaven
I’ve since written this better guide to getting started: http://rawpedia.rawtherapee.com/Getting_Started
It would make sense to move the “Raw” tab to the front, but as for the rest it ranges from being unclear to being arbitrary.
I’m wondering if 
Now the trick is to fix the indiscriminately part to targeted adjustments focused on a result. That is, experiment with the how and why until you get a feeling for it to best understand what will happen on future images. (Then pay it forward and come back to write an article about it…