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Author Topic: Issues of Noise Reduction  (Read 1499 times)
walter.sk
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« on: December 12, 2012, 04:44:17 PM »
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In the segments of the LR4 tutorial that deal with sharpening and noise reduction, Jeff adjusts the sharpening first, even with an ISO 12,800 image.  He then works with the noise reduction sliders, and then goes back to tweak the sharpening adjustments.

I have found it difficult to evaluate the sharpening settings until I have first done the best balance of the noise controls, with sharpening turned off completely.  I am careful to avoid that plastic look that comes from too much Luminance NR, and bring back as much detail and contrast as possible without making the image look noisy again.  Then I go to the sharpening controls, adjusting the radius large enough to not sharpen the noise, and raising the amount slider just below the point where stuff starts looking crunchy at 1:1.  I then move the Sharpening detail slider and masking to taste, and tweak all the sharpening sliders.

Next, I try tweaking the noise sliders to squeeze more detail if possible, and with some images I add a bit of grain.

Again, it seems easier to me to start no with sharpening, isolate the actual noise, take care of the real noise as best as possible, then do the sharpening.

Am I missing something with this approach? Is one way more effective than the other, or is it just a matter of personal preference?

I also am not sure whether I can get better results by doing the NR before the opening the shadows, or doing my big tonal moves before working on noise reduction.  But it seems that knocking out the noise first and then brightening the shadows ends up at least as clean of noise.

Your experiences?
« Last Edit: December 12, 2012, 04:45:56 PM by walter.sk » Logged
Tony Jay
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« Reply #1 on: December 12, 2012, 06:30:49 PM »
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Walter, IMHO:
1. Defer noise and sharpening adjustments until tone and colour adjustments are sorted.
2. Radius adjustments are related to the detail in the scene (high detail - low(er) radius, low detail - high(er) radius) and not the noise specifically. (I am not suggesting ignoring noise as an issue here - merely that there is a hierarchical approach.)
3. Consider using local sharpening adjustments for specific areas, such as eyes, or perhaps say a landscape where a significant part is high in intricate detail (trees and rocks) and a significant part, is, say sky, with little detail.
4. My RAW images very rarely need much colour noise suppression (yours may vary).
5. Luminance noise suppression I only look at once an appropriate sharpening mask has been applied. (The sharpening mask has the designed effect of limiting sharpening in areas where the mask is in effect but is also a very useful tool for highlighting the presence of noise in places like skies and the effect of noise reduction once applied.) There is very definitely a trade-off with noise reduction (reduces fine detail) and sharpening (enhances fine detail) - sometimes it takes prints or otherwise viewing the image in its final output form to decide which is the best balance.
6. Local noise suppression should also be considered where appropriate to avoid the effects of global noise suppression.

Tony Jay
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walter.sk
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« Reply #2 on: December 13, 2012, 12:01:37 PM »
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Walter, IMHO:
1. Defer noise and sharpening adjustments until tone and colour adjustments are sorted.
I did more tests and I agree. 
2. Radius adjustments are related to the detail in the scene (high detail - low(er) radius, low detail - high(er) radius) and not the noise specifically. (I am not suggesting ignoring noise as an issue here - merely that there is a hierarchical approach.)
I've been aware of this.
3. Consider using local sharpening adjustments for specific areas, such as eyes, or perhaps say a landscape where a significant part is high in intricate detail (trees and rocks) and a significant part, is, say sky, with little detail.
Have done that
4. My RAW images very rarely need much colour noise suppression (yours may vary).
I have found that the default LR4 color noise settings are OK, and I have on occasion been able to reduce the amount.
5. Luminance noise suppression I only look at once an appropriate sharpening mask has been applied. (The sharpening mask has the designed effect of limiting sharpening in areas where the mask is in effect but is also a very useful tool for highlighting the presence of noise in places like skies and the effect of noise reduction once applied.) There is very definitely a trade-off with noise reduction (reduces fine detail) and sharpening (enhances fine detail) - sometimes it takes prints or otherwise viewing the image in its final output form to decide which is the best balance.
I hadn't thought of using the masking to show the degree of noise.
6. Local noise suppression should also be considered where appropriate to avoid the effects of global noise suppression.
This brings me to another question.  For both the adjustment brush's sharpening and noise controls: Do they use the settings from the Detail panel, varying only the amount that those settings are applied, or do they work with their own internal default settings?
Tony Jay
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Dan Glynhampton
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« Reply #3 on: December 13, 2012, 12:29:23 PM »
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Tony has given some excellent detailed advice, but to answer your question more generally I too find that in images with a lot of luminance noise you can't "see the wood for the trees" when sharpening, so I've got into the habit of running up the noise reduction slider immediately before the sharpening of such images.  I don't spend time fine tuning the noise reduction at this stage, just run it up high enough so I can see what's going on with the sharpening, then resume the "top to bottom" approach within the detail panel.

It works for me, but YMMV.

Dan
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walter.sk
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« Reply #4 on: December 13, 2012, 06:25:43 PM »
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I too find that in images with a lot of luminance noise you can't "see the wood for the trees" when sharpening, so I've got into the habit of running up the noise reduction slider immediately before the sharpening of such images.  I don't spend time fine tuning the noise reduction at this stage, just run it up high enough so I can see what's going on with the sharpening, then resume the "top to bottom" approach within the detail panel.
Dan
Sounds like an approach that would work for me.
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bns
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« Reply #5 on: December 14, 2012, 04:05:53 AM »
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"This brings me to another question.  For both the adjustment brush's sharpening and noise controls: Do they use the settings from the Detail panel, varying only the amount that those settings are applied, or do they work with their own internal default settings?
Tony Jay"


Adjustment brush (and gradient filter) work with settings of detail panel, only varying the amount, either positive or negative.

Boudewijn Swanenburg
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If it can't be done with Lightroom, I don't do it.
BartvanderWolf
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« Reply #6 on: December 14, 2012, 04:18:15 AM »
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In the segments of the LR4 tutorial that deal with sharpening and noise reduction, Jeff adjusts the sharpening first, even with an ISO 12,800 image.  He then works with the noise reduction sliders, and then goes back to tweak the sharpening adjustments.

I have found it difficult to evaluate the sharpening settings until I have first done the best balance of the noise controls, with sharpening turned off completely.

Hi Walter,

What this boils down to, IMHO, is that the concept of Capture sharpening is not communicated (or understood) clearly enough. When we adopt the principle of Capture/Creative/Output sharpening, then that Capture sharpening is inevitably linked to the hardware, i.e. the lens and camera, and is therefore a given quantity (as can be proven by analysing the image blur), for a given aperture setting.

That required sharpening quantity is a given, irrespective of whatever noise is in the image data, due to (low) exposure and/or data amplification. Trying to control the noise with reduced Capture sharpening, defeats the whole purpose of the Capture sharpening stage of image processing, which is to counteract the losses of sharpness due to the Capture process.

Because the Capture sharpening might boost some of the noise at the specific spatial sharpening frequencies, it can be beneficial to restrict Capture sharpening to those areas that have some detail worth of sharpening by using a high-pass mask (only for the detail, and thus low-pass for more uniform e.g. sky areas).

The difficulty with Lightroom is that it is tempting to also address Creative sharpening with the same Capture sharpening dialog but that would be a mistake, again IMHO. This is demonstrated by the difficulty to find some sort of balance between the noise reduction settings and the sharpening dialog settings, they influence each other.

Things become a lot simpler if we adhere to a strict separation between the Capture sharpening, together with (modest) Noise reduction and Masking, and the rest of the postprocessing steps such as Creative sharpening with the Adjustment brush (which also allows to control the sharpening/noise in specific areas of the image).

Cheers,
Bart
« Last Edit: December 15, 2012, 03:35:18 AM by BartvanderWolf » Logged
Tony Jay
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« Reply #7 on: December 14, 2012, 04:48:09 AM »
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"This brings me to another question.  For both the adjustment brush's sharpening and noise controls: Do they use the settings from the Detail panel, varying only the amount that those settings are applied, or do they work with their own internal default settings?
Tony Jay"


Adjustment brush (and gradient filter) work with settings of detail panel, only varying the amount, either positive or negative.

Boudewijn Swanenburg

Absolutely correct: positive adjustment increases sharpening or noise reduction from baseline, negative adjustment reduces sharpening or noise reduction from baseline.
Baseline is whatever sharpening or noise reduction has already been applied globally.

Tony Jay
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Tony Jay
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« Reply #8 on: December 14, 2012, 04:58:41 AM »
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Hi Walter,

What this boils down to, IMHO, is that the concept of Capture sharpening is not communicated (or understood) clearly enough. When we adopt the principle of Capture/Creative/Output sharpening, then that Capture sharpening is inevitably linked to the hardware, i.e. the lens and camera, and is therefore a given quantity (as can be proven by analysing the image blur). That quantity is irrespective of whatever noise is in the image data, due to exposure and/or data amplification. Trying to control the noise with reduced Capture sharpening, defeats the whole purpose of the Capture sharpening stage of image processing, which is to counteract the losses of sharpness due to the Capture process.

Because the Capture sharpening might boost some of the noise at the specific spatial sharpening frequencies, it can be beneficial to restrict Capture sharpening to those areas that have some detail worth of sharpening by using a high-pass mask.

The difficulty with Lightroom is that it is tempting to also address Creative sharpening with the same Capture sharpening dialog but that would be a mistake, again IMHO. This is demonstrated by the difficulty to find some sort of balance between the noise reduction settings and the sharpening dialog settings, they influence each other.

Things become a lot simpler if we adhere to a strict separation between the Capture sharpening, together with (modest) Noise reduction and Masking, and the rest of the postprocessing steps such as Creative sharpening with the Adjustment brush (which also allows to control the sharpening/noise in specific areas of the image).

Cheers,
Bart

Bart is correct.
In the Lr4 tutorial Jeff does not make a big deal of the nuances that Bart is referring to.
However, in the "Camera to Print and Screen" tutorial Jeff does deal with this issue of capture vs creative vs output sharpening very well in my opinion.
I also have no doubt that he will formalize these concepts excellently in his next book due out in 2013.

Tony Jay
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Dan Glynhampton
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« Reply #9 on: December 14, 2012, 05:54:59 AM »
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Walter – on further reflection on this question it occurs to me that Jeff does give an implicit acknowledgement that it can be desirable to apply some noise reduction first, since there’s a segment of the LR4 tutorial where he demonstrates setting a default level of noise reduction for a particular camera/ISO combination.  With that default set, all subsequent images imported from that camera at that ISO will have the noise reduction increased above the usual setting.

So if you’re finding high levels of luminance noise interfere with your sharpening process I wouldn’t hesitate to run up the noise slider first as I suggested earlier in the thread, and if you process sufficient high noise images then set a default level as Jeff demonstrates.

Dan
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walter.sk
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« Reply #10 on: December 14, 2012, 11:45:17 AM »
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So if you’re finding high levels of luminance noise interfere with your sharpening process I wouldn’t hesitate to run up the noise slider first as I suggested earlier in the thread, and if you process sufficient high noise images then set a default level as Jeff demonstrates.
Dan
That seems to be the best approach for me.  Using the 5DIII I usually don't even worry about the noise at ISO800 or below, except for a small bit of Luminance nr.  But I had occasion to shoot some performances in a miserably lit room where I had to shoot at high enough shutter speeds to avoid subject blur, and ended up at ISO 6400 and 12800.  Because of having to bring out detail in shadow areas as well the noise became prominent, although easy enough to tame in LR or ACR.

Part of the problem was forgetting about the difference between capture sharpening and creative sharpening, and the idea of making NR settings as defaults for specific high ISO settings to use as starting points will cure my main sharpening/nr problems.
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