Grain accentuation after raw processing, Olympus OM-DEM-5 Mkii

[rawful]

Hi All,

My first post here, so hello everyone

I have been using RawTherapee (5.8.0 Mac) for a few months now and I love it. I’ve been getting great results with exposure, colour etc. but I’m having trouble with accentuated grain on my images. After processing, I’m seeing a crystaline grain pattern which isn’t there on the camera’s JPEG output. I’m using an Olympus OM-D EM-5 Mkii. Please see the below examples (click to zoom for better detail). The bee is at ISO 200 while the wind turbine is at ISO 800.

I expect to have some grain, especially at ISO 800 and with increased contrast, but it looks like RawTherapee really makes a right meal of it. Is this something other people have experienced? Is this to do with the demosaicing? Is there something I need to know about the EM-5 and how to treat images from it?

I would love to resolve this so that my processed raws look as smooth as the JPEGs off the camera.

Thanks in advance

[Claes]

Hi @rawful and welcome!

Are you sure that is grain?
My rusty memory says that we had a thread about just that some time ago…
I’ll see if I can dig it up…

Found it. Hm. Not really applicable: Film grain suggestion

What if you try some denoise modules?

Have fun!
Claes in Lund, Sweden

[rawful]

Hi @Claes,

I’m not sure this is technically ‘grain’ - It may be being introduced by one of the raw processing features. It does look slightly un-natural, especially on the image of the bee. It looks like the effect of a mathmatical process rather than a natural noise. Changing the demosaic mode does change things but not for the better. I use AMaZE as standard. Perhaps the EM-5 has some unusual bayer configuation?

‘Noise reduction’ is applied to these images, and it does a great job on the colour noise from the sensor. It doesn’t seem to affect the detail. ‘Impulse noise reduction’ doesn’t seem to do much other than wipe out ‘dust-like’ details, such as the bolts on the wind turbine cowling. ‘Denoise and refine’ seems to have no effect at all, regardless of slider positions. :-/

[Wayne_Sutton]

Hi @rawful , I get this sometimes with my E-M10 MkII when Capture Sharpening is enabled and the Radius and Threshold are in “Automatic” mode. I usually turn off the Capture Sharpening until I have finished processing the image and then adjust it manually at the end.

[Jade_NL (Jacques)]

@rawful

‘Noise reduction’ is applied to these images, and it does a great job on the colour noise from the sensor. It doesn’t seem to affect the detail.

[…]

regardless of slider positions.

I’m not familiar with the E-M5/E-M10, so do take a look at Wayne’s suggestions (good advise regardless of Camera brand/type), but I do want to mention the following just in case:

You mention using the sliders in the noise reduction module. I’m assuming that you are talking about the Luminance section; I would strongly suggest that you use the curve instead of the slider (can be set in the Luminance control pull down). This way you have more control how much a specific luminance area gets targeted. This will protect those areas that do not need (that much) noise reduction.

[marter (Martin Werner)]

I would like to see the raw and pp3, because i estimate, its the result of a combination of sharpening and (local) contrast.

[KarlMagnusLarsson (Magnus Larsson)]

I see the same thing as @rawful points out in out of focus areas of shallow depth of field captures, like macro or portraits with fast portrait lenses. For me the solution is along the lines of what @Wayne_Sutton states:

1. Turn off Raw tab | capture sharpening and Detail tab | Sharpening

2. Activate sharpening contrast mask (shortcut: p)

3. Activate capture sharpening. Increase Raw tab | capture sharpening | contrast threshold until the out of focus areas are no longer affected by capture sharpening.

4. If I need further creative sharpening I do the same thing with detail tab | sharpening | contrast threshold. I temporarily deactivate capture sharpening and Activate sharpening contrast mask (shortcut: p), and increase the threshold until the out of focus areas are no longer affected by unnecessary sharpening.

5. Finally I reactivate Raw tab | capture sharpening and (if needed) detail tab | sharpening and lower the iterations of capture sharpening.

At stage 5 I usually have a sharp image without accentuated grain in out of focus areas.

[nosle]

I agree that it looks like capture sharpening. Ages ago I asked on this forum if smooth gradients could be more specifically excluded from sharpening but @heckflosse, if I remember correctly suggested it can’t .

The issue as I naively see it is that gradients may have adjacent pixel values different enough to trigger sharpening. But there are currently no means to detect or control the behaviour when pixels are part of a long chain of continuous changing values IE gradient or large radius blur.

My defaults use capture sharpening but for large aperture portraits I have a profile that disables global sharpening and sets up a local edit spot with some detail enhancing modules.

[KarlMagnusLarsson (Magnus Larsson)]

Local edit spots are a great solution to the problem. I use it as well, that is, disable global sharpening and only sharpen certain spots as @nosle points out.

However, the ‘Local’ tab is only available in development builds. It is not available in RawTherapee 5.8 that @rawful is using.

[ilia3101 (Ilia Sibiryakov)]

This is definitely capture sharpening! Always worth turning off.

[rawful]

Hi All,

Firstly, apologies for the delay in replying. My computer has been completely tied up processing a monster photogrammetry map, so I all my cores have been maxed out for days and I haven’t had the CPU available to run RawTherapee at a sensible speed!

Thank you all so much for the very useful replies. @KarlMagnusLarsson ; I did not know about the sharpening contrast mask - this is super useful and I can see the problem straight away, literally in black and white! Capture sharpening contrast threshold was definitely too low and causing problems.

I have re-processed the image following the advice given, and ended up with the following changes:
Local contrast: disabled
Defringe: linear
Sharpening: disabled
Capture Sharpening > Contrast threshold: raised to 63

On a side note, it’s interesting that defringe seems to be a lot more effective in ‘linear’. Perhaps it’s just this image but I will be experimenting further.

I think you’ll agree that the new image (right) is much better. There is still some grain but I think an acceptable level, considering this photograph was shot at ISO800 on a MFT sensor. I would be interested to know thoughts on whether it would be possible to reduce noise further. However, my feeling is that the camera generated JPEG (left) is benefiting from JPEG compression smoothing out some of the noise.

Is it possible in RawTherapee to change the default settings for capture sharpening, defringe etc. so I don’t have to change it each time?

I’m looking forward to the release of 5.9 and using local adjustments. Do we have any idea when the release date is likely to be?

Here are the old and new PP3 files for those who might be interested:
new.out.pp3 (11.1 KB)
old.out.pp3 (11.6 KB)

Again, Thank you all so much.

[rawful]

Ok, a further update, having dived further into noise reduction - using luminance curve as suggested by @Jade_NL. This definitely makes all the difference.

I think I’m pretty close to the camera JPEG now, if not slightly better! This has been so helpful - thank you. I hope this thread can help others solve the same issue in the future

[ChasingShadows (Karlheinz Lehmann)]

@rawful

Is it possible in RawTherapee to change the default settings for capture sharpening, defringe etc. so I don’t have to change it each time?

Have a look at Creating processing profiles for general use - RawPedia (rawtherapee.com) and here Dynamic processing profiles - RawPedia (rawtherapee.com) where you can automatically choose a profile based on values like ISO or camera type and so on

[priort (Todd Prior)]

Any chance you have the default sharpening on?? I dont’ have issue with capture sharpening but the default sharpening can create artifacts for me on many images…

Reading closer I think you did but now you have turned it off…I found many times just doing that would take away a lot of artifacts and minimize having to use lum denoise or at least only a touch of it…