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Author Topic: Do RAW converters apply "hidden" sharpening and noise reduction?  (Read 11061 times)
Gurglamei
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« on: March 30, 2009, 05:27:26 AM »
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(Sorry about the typo, I am using LR 2.3...)

Since I recieved a copy of C1 ver 4 as a "free gift" when I purchased my Nikon D700, I decided to do a small comparison with Lightroom 2.3. I have read some posts claiming C1 really gets the detail from Nikon images.

Now, to do the test I set all sharpening and noise reduction to zero, as I assumed this would create an equal baseline.

On some images the C1 processing shows a cleaner image. I can easier read tekst, se details in brick walls etc. However it also appears to "even out" some irregularities.  The difference appeared to be a matter of some noise reduction and sharpening. Sure enough, I discovered that by adding a bit of noise reduction, clarity and sharpening in LR I created an image almost identical to the result form C1 with "no sharpening". Actually I liked the LR resault better.

My question is simply if when one designs a RAW converter, must one also decide on a default level of sharpening and noise reduction which is applied to each and every image processed by the converter that the user can not adjust with sliders etc in the application.  In the sence that there is no such thing as a RAW conversion without any kind of sharpening or noise reduction, just a matter of where the developers decide to stop and leave further adjustments to the user of the application?
« Last Edit: March 30, 2009, 05:30:23 AM by Gurglamei » Logged
Max Penson
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« Reply #1 on: March 30, 2009, 06:19:29 AM »
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There are many reasons to that, but I think the main reason is that most modern demosaicing algorithms are designed to "handle" noise during demosaicing. So there is simply no NR OFF option, just less. Also, some demosaicing algorithms actually produce unpleasing maze like results on flat areas. So a minimum amount of filtering must be applied to correct the artifact.
Other than these technical reasons, there is the user aspect of image quality. No matter how good you document your software, most of the users are unable to understand how to sharpen un-filtered images.
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Panopeeper
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« Reply #2 on: March 30, 2009, 10:25:02 AM »
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Re sharpening: the action trying to mitigate the effect of the anti-aliasing filter and of the mushy nature of demosaicing has to be done in the raw conversion stage. The output sharpening should not be done at this stage.

Re noise reduction: the noise depends on the actual illumination of the pixels (light capturing) and on the ISO; as the different color filters over the sensels block different proportions of the infalling light, the three raw channels (in case of a Bayer type sensor) show different levels, i.e. different level of noise. Therefor the noise can be reduced most effectively before the actual raw conversion, directed towards the noisy channel(s). Demosaicing and particularly the color space conversion are "mixing" or "distributing" the noise among the RGB channels, noise reduction after that stage is inherently more destructive of details than before.
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Gabor
Graeme Nattress
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« Reply #3 on: March 30, 2009, 11:18:14 AM »
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Each and every different demosaic algorithm, and there are many, will behave differently to inherent sharpness and noise without actually having sharpening or denoising as a specific element of the algorithm. Although demosaicing is just often thought of as figuring out the colour at each pixel location, often more processing is done at that point for that point, where you have linear light un-matrixed colours, is often the most appropriate place in the pipeline to apply it. That processing could be NR, and could be sharpening.

Graeme
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madmanchan
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« Reply #4 on: March 30, 2009, 01:57:20 PM »
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Gurglamei, part of your question can really be restated as: "When a slider in a raw converter has the value of 'zero' -- what does that really mean?" Some raw converters will certainly do noise reduction even when the noise reduction slider is set to zero. In other words, "zero" doesn't necessarily mean "completely disabled."

It also depends on your definition of noise reduction. At a technical level, as explained above, the demosaic step involves interpolation. A common approach (though not required) among demosaic algorithms is that the original pixel values are preserved, unmodified. For example, the original green pixel values at green pixel locations are maintained, while the demosaic needs to synthesize green values as the red & blue pixel locations. That synthesis usually occurs by some form of interpolation, which almost always reduces noise. That is, when using standard interpolation methods such as bicubic, bilinear, etc. the variance of the interpolated green pixels is less than the variance of the original green pixels. Hence, taken as a whole, the variance of all of the green pixels (both original + interpolated) has decreased. Thus, one can argue that ALL such demosaic methods (which basically includes all of the commercial ones) include some amount of noise reduction during the demosaic.
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Gurglamei
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« Reply #5 on: March 30, 2009, 03:51:39 PM »
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Thank you all for your answers to my question.

Although this is a bit more technical than I thought, I think I "get the picture".  I gather that to compare RAW converters one can not "set all sliders to zero" and compare the result. To compare one actually has to tweak all possible settings in each converter to the optimal level for the image. (And, since I am much more familiar with Lightroom than C1, I am likely to achieve a better result with LR).
« Last Edit: March 30, 2009, 03:58:42 PM by Gurglamei » Logged
madmanchan
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« Reply #6 on: March 30, 2009, 05:17:31 PM »
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Yes, frankly, that is one of the issues that makes comparing raw converters as complex as comparing cameras.
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Dale_Cotton2
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« Reply #7 on: March 30, 2009, 05:56:23 PM »
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Quote from: Gurglamei
To compare one actually has to tweak all possible settings in each converter to the optimal level for the image.
Each converter makes a finite number of decisions about what is the best approach for each raw file. Just to get started: there are lots of demosaicing algorithms out there to choose from. It would be great if raw converters had enough smarts to switch between them based on the image at hand. (Thankfully, many of these algorithms seem to be in the public domain, so developers don't even have to deal with patent issues.) Raw Therapy lets the user select from a few options. Lightroom does not (but for all I know it automatically makes a selection based on some heuristic algorithm).

Another issue is what colour profile to apply. LR at least now offers users a spectrum of choices for each camera it supports. More importantly to me, it offers a brilliant set of HSL sliders and the option of saving settings per camera, so having found the most accurate adjustment to a given generic profile for my camera, I simply tell LR to apply that to all subsequent images.

Ultimately, to get the best possible results, I would have to buy and install all available converters, know how to take maximal advantage of each, process every important image in each, then compare the results from each, finally making a judgment call as to which conversion to go forward with for every single image. Instead, I evaluated several, stuck with LR (actually, I'm still back at ver 1.4) and RT, and use LR except for particularly images, in which case I use RT then pass the output to Noise Ninja. After that, back in Photoshop, I try to adjust the colours/tones of the result to match the LR output as closely as possible, since the LR colour will simply be correct and the RT colour will simply be a dog's breakfast. ;)

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Panopeeper
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« Reply #8 on: March 30, 2009, 06:32:05 PM »
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Quote from: Dale_Cotton2
Each converter makes a finite number of decisions about what is the best approach for each raw file
The TOPIC of this thread is  Do RAW converters apply "hidden" sharpening and noise reduction?
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Gabor
seanm
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« Reply #9 on: April 05, 2009, 07:19:57 AM »
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I was wondering the same thing myself.
So do most of you apply sharpening and noise reduction at the RAW conversion level, or do you prefer to leave this to a later PP step using for example Noise Ninja? My experience of RAW converters is limited to Canon's free one plus Photoshop's.
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barryfitzgerald
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« Reply #10 on: May 03, 2009, 05:21:37 AM »
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As far as I am aware, only DxO and LR/ACR apply noise reduction to raw files that cannot be disabled or bypassed. I have not tried DxO for some time, so I am not 100% sure on that one.

Looking at high ISO results from C14 and LR2, I believe you can get significantly better results from the former, with some careful use of a 3rd party noise reduction program, after the raw conversion. However, some say DxO does great things for high ISO, with NR. Maybe this is the case. I cannot say I find ACR to be satisfactory in this respect, and in particular, the smearing effect on luminance noise does not make for good prints, the colour noise levels are significantly higher too.

This is a long standing issue, that is in need of work, IMO ;-)

Doing NR on raw with no option to disable it, is just as bad as a certain maker's experiment with NR on raw (which was at the time fixed, and with no option to disable it)
« Last Edit: May 03, 2009, 06:24:00 PM by barryfitzgerald » Logged
MarkL
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« Reply #11 on: May 04, 2009, 11:46:35 AM »
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I'm sure NX2 does sharpening (likely to be deconvulsion based) with sharpening set to zero since the files come out much sharper than ACR/LR
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Doyle Yoder
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« Reply #12 on: May 09, 2009, 09:54:48 AM »
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Quote from: MarkL
I'm sure NX2 does sharpening (likely to be deconvulsion based) with sharpening set to zero since the files come out much sharper than ACR/LR

Or could it be the NR that ACR/LR is applying?
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MarkL
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« Reply #13 on: May 11, 2009, 06:57:49 AM »
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Quote from: DYP
Or could it be the NR that ACR/LR is applying?

Could be, though I see the same in raw therapee and dxo (with no lens module) with sharpening off and NR off.
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robgo2
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« Reply #14 on: August 03, 2009, 08:50:43 PM »
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Quote from: barryfitzgerald
As far as I am aware, only DxO and LR/ACR apply noise reduction to raw files that cannot be disabled or bypassed. I have not tried DxO for some time, so I am not 100% sure on that one.

I believe that DxO removes noise before demosaicising, and it may be unique in that respect.  I do not know if some NR is applied as a default, however.  There are NR sliders in the Prepare window.  In any case, it seems to do a superior job of noise removal.

Rob
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« Reply #15 on: August 22, 2009, 04:21:09 PM »
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You can disable Sharpening in C1, not sure about Noise Reduction though.
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Doug Peterson
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« Reply #16 on: August 24, 2009, 12:24:41 PM »
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Also note that all of these topics will take on a new dimension if/when you start working with files which were captured either at high ISO, underexposed, or were taken in mixed lighting (because changing the white balance in post means, effectively, pushing the underexposed color - generally pushing blue data in tungsten light).

You may find that you prefer C1's look when processing these "problematic" files. Or you may not. As with your evaluation of a "normal" image the difference is only partly technical, and partly a matter of personal taste.

Doug Peterson
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