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Author Topic: Noise removal?  (Read 27832 times)

CynthiaM

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Noise removal?
« Reply #20 on: June 19, 2008, 08:34:16 am »

Thanks for all of your responses.  I think I have a better handle on how to handle noise.
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Gordon Buck

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« Reply #21 on: June 19, 2008, 11:54:58 am »

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Fine if that works for you, but your approach is contrary to all expert opinion that I have seen. You have not presented any of your results, but I wonder if your testing is sufficiently intensive to reach your conclusion.[a href=\"index.php?act=findpost&pid=202264\"][{POST_SNAPBACK}][/a]

No doubt my Photoshop skills need improving and will improve but I strongly suspect that many people making a simple comparison using light ACR sharpening followed by Noiseware will be pleasantly surprised at the results.  At the very worse, the results are OK and, I'd say, preferable.  

Note that my original post has been edited.  Of course, one of the variations was without ACR sharpening immediately followed by PK Capture Sharpener and then Noiseware.  In the original post, I transposed the order.

I've actually tested quite a few files and will be testing more.
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Mark D Segal

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« Reply #22 on: June 22, 2008, 11:04:53 pm »

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Fine if that works for you, but your approach is contrary to all expert opinion that I have seen. You have not presented any of your results, but I wonder if your testing is sufficiently intensive to reach your conclusion.

In his sharpening book, Bruce Fraser pointed out that many noise reduction algorithms produce images that can not subsequently be sharpened without bringing back the noise in full glory. Personally, I found this to be the case with Noiseware and PK capture sharpening. For high volume work in shooting sporting events, I found the best approach was to do the NR and sharpening in Noiseware. This apporoach allows parametric editing, NR, and sharpening in Photoshop with ACR without the necessity of producing intermediate TIFF files.

Bill
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Gordon could be getting the results he talks about because the kind of sharpening he's doing in ACR does not affect smooth areas or areas with little detail, such as skies, skin and very dark tones, which is where most of the noise usually shows. It's really hard to conceive of any sharpening that sharpens noise being "a good thing" regardless of what tools one uses.

As for the combination of Noiseware and PK Capture Sharpen, this is my usual combination whenever I need to reduce noise (not often these days) and it works well. I have Noiseware set to quite high values for noise reduction e.g. 70~80% (but usually defaults for noise identification), maximum detail protection; then in PK Capture Sharpen I often use the Superfine setting eventhough the image may not look as if it has much high-frequency information. With this combination of settings the noise does not return as a result of capture sharpening.

I find it useful to examine my 1Ds3 files at both 50% and 100% display magnification, as each allows one to see different things - be it the overall likely result in a 13*19 inch print or fine artifacts as the case may be.
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bjanes

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« Reply #23 on: June 23, 2008, 10:00:51 am »

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As for the combination of Noiseware and PK Capture Sharpen, this is my usual combination whenever I need to reduce noise (not often these days) and it works well. I have Noiseware set to quite high values for noise reduction e.g. 70~80% (but usually defaults for noise identification), maximum detail protection; then in PK Capture Sharpen I often use the Superfine setting eventhough the image may not look as if it has much high-frequency information. With this combination of settings the noise does not return as a result of capture sharpening.

I find it useful to examine my 1Ds3 files at both 50% and 100% display magnification, as each allows one to see different things - be it the overall likely result in a 13*19 inch print or fine artifacts as the case may be.
[a href=\"index.php?act=findpost&pid=202946\"][{POST_SNAPBACK}][/a]

Mark,

Or differences could be related to the camera. Your 1Ds3 has relatively low noise, whereas my Nikon D200 has high noise, especially at ISO 1600 and in the blue channel when one is shooting in tungsten illumination. Here is a representative shot taken under tungsten illimination at ISO 1600 and which was slightly underexposed and needed some positive exposure compensation in ACR. The blue channel is on the right. The RGB shows yellow splotches on the skin where there is essentially no blue signal.

[attachment=7173:attachment]

And here is a composite shot showing various NR and sharpening combinations. On the right is the default NoiseWare (sharpening = 5). The middle image shows the default NW with PK superfine sharpening. On the left, I set sharpening to zero in NW and sharpened with PK superfine.

[attachment=7174:attachment]

Note the re-appearance of noise along the hairline, ears, eyes, nose and other areas. Personally, I prefer the default NW image. Of course, there are a large number of possible permutations, and I used defaults to simply matters. All images are at 100%.

I now have a D3 and find that NR is often not needed even at ISO 3200 and my current situation may be similar to yours. Thanks for your input, which is always appreciated.

Bill
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Mark D Segal

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« Reply #24 on: June 23, 2008, 10:25:00 am »

Bill,

Yes indeed, both the 1Ds3 and the D3 show remarkably little noise at high ISO and that makes a huge difference to the post-processing challenge. That blue channel illustration you provide is quite a shocker; but for the majority of people who can't or won't put high megabucks into a DSLR and still expect good results at high ISO, this is approximately what they can expect to get, especially with under-exposure, so really best practice with exposure and post-capture workflow becomes all the more important.

Looking at the three extracts in your second illustration without reading what they are (to minimize "intellectual contamination") just visually on my 1600*1200 resolution LaCie 321 none of them stands out as really better than the others. You would probably see more differentiation using the original full resolution images.  But in all cases, I would assume you are doing the noise reduction before sharpening, right?

Mark
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bjanes

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« Reply #25 on: June 23, 2008, 12:05:39 pm »

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Bill,

Yes indeed, both the 1Ds3 and the D3 show remarkably little noise at high ISO and that makes a huge difference to the post-processing challenge. That blue channel illustration you provide is quite a shocker; but for the majority of people who can't or won't put high megabucks into a DSLR and still expect good results at high ISO, this is approximately what they can expect to get, especially with under-exposure, so really best practice with exposure and post-capture workflow becomes all the more important.
[a href=\"index.php?act=findpost&pid=203063\"][{POST_SNAPBACK}][/a]

Mark,

Actually, the shot that I chose is approaching worst case, since it was underexposed and the illumination was about 2000K (for WB in ACR). With better exposure and in daylight, the blue channel is considerably better. Nonetheless, with the D200 at ISO 1600 exposure to the right is critical for best signal:noise. However, in difficult conditions, ETTR can run counter to getting enough shutter speed and one does not always get optimal exposure in action shots.

With the D3 at high ISO, I usually use the built in ACR NR if needed (usually not), followed by the built in ACR sharpening (which, as you know, is based on Bruce Fraser's workflow as is PKSharpener). I often prefer the fine grained noise pattern of the D3 to the softness introduced by NR.  The PK output sharpening works well with this workflow. Is that what you are finding with the 1Ds3?

Quote
Looking at the three extracts in your second illustration without reading what they are (to minimize "intellectual contamination") just visually on my 1600*1200 resolution LaCie 321 none of them stands out as really better than the others. You would probably see more differentiation using the original full resolution images.  But in all cases, I would assume you are doing the noise reduction before sharpening, right?

Mark
[a href=\"index.php?act=findpost&pid=203063\"][{POST_SNAPBACK}][/a]

The differences did not show as well as I had hoped, so here is another shot with NoiseWare defaults + PK fine edge on the left and NoiseWare detaults only on the right and at 200%. I uploaded to my web site as a PNG to avoid JPEG artifacts. Yes, I always do NR before any sharpening.

Bill

« Last Edit: June 23, 2008, 12:26:43 pm by bjanes »
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Mark D Segal

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« Reply #26 on: June 23, 2008, 01:01:44 pm »

Bill,

Yes, more obvious now. I do find it peculiar that a sharpening algorythm should pick up noise that has already been "reduced", but your evidence seems to point that it may. This must mean that the noise reduction is not adequate for certain edges to remain invisible to the sharpening. But then, if one reduced the noise even more (i.e. pushed well beyond the defaults) one may begin to impair desirable detail even with capture sharpening. Careful compromises!

Mark
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Gordon Buck

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« Reply #27 on: June 23, 2008, 01:39:35 pm »

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Yes, I always do NR before any sharpening.
[a href=\"index.php?act=findpost&pid=203090\"][{POST_SNAPBACK}][/a]

Bill, realizing that ACR sharpening prior to noise reduction is not your recommendation, could you process the same image with modest ACR "capture" sharpening followed by Noiseware default?
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gmitchel

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« Reply #28 on: June 24, 2008, 09:15:05 am »

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Bill,

Yes, more obvious now. I do find it peculiar that a sharpening algorythm should pick up noise that has already been "reduced", but your evidence seems to point that it may. This must mean that the noise reduction is not adequate for certain edges to remain invisible to the sharpening. But then, if one reduced the noise even more (i.e. pushed well beyond the defaults) one may begin to impair desirable detail even with capture sharpening. Careful compromises!

Mark
[{POST_SNAPBACK}][/a]

I'm not surprised.

Noise reduction software doesn't remove noise. It makes it less obvious. It can be accomplished in a number of ways, but the essence is the reverse of sharpening. Neighboring pixels are examined to determine whether the values for a pixel are significantly different *WHERE* little variation is expected in terms of color and/or luminosity. The contrast between those pixels and their neighbors is reduced.

The Median filter, for example, is a fairly blunt tool for noise reduction. The neigboring pixels are consulted and their median value (sort the values and take the middle value) is used to adjust the pixel. This "smooths out" variation and reduces noise.

Sophisticated tools like NeatImage, Noise Ninja, and Noiseware have more sophisticated algorithms for determining noisy pixels and for replacing their values, but in essence they reduce contrast between noisy pixels and their neighbors.

Sharpening software can still detect the contrast between noisy pixels and their neighbors *AND* emphasize the contrast, undoing some/all of the noise reduction.

That's why I refer to noise reduction and capture sharpening as antagonistic in my eBook and my video on sharpening.

[a href=\"http://www.thelightsright.com/SharpeningYourPhotographs.html]http://www.thelightsright.com/SharpeningYourPhotographs.html[/url]

You can reduce noise to the point where capture sharpening cannot make it more visible. The resulting artifacts -- a plastic-like appearance from loss of significant details -- will likely be worse than some residual noise.

If you do not use layers masks, capture sharpening and noise reduction will largely cancel out. Depending which is more aggressive in effect, you will either end up sharpening noise or softening significant details.

Capture sharpening is best done with a layer mask that restricts sharpening to the edges. ACR and LR now include some edge masking. Focal Blade and Photokit Sharpener give you direct control over edge masking. So do my actions and scripts (there are free actions and scripts for noise reduction, masking, and sharpening on my site).

I strongly recommend noise reduction on a layer and using a surface mask to keep noise reduction away from the edges. That will allow you to use more aggressive noise reduction settings in many cases without losing significant details. That can make it less likely for noise to reemerge after capture sharpening. I have a free script that can automate the generation of surface masks. There are even options to limit the masks to tonal/color ranges (e.g., the shadows).

It takes more work, but if you can restrict noise reduction to just the features where it's most needed, like the shadows, you can be more aggressive with the noise reduction settings. Restricting noise reduction was the #1 motivation behind my masking script.

http://www.thelightsright.com/TLRProfessionalMaskToolkit.htm

Enjoy!

Mitch
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CynthiaM

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« Reply #29 on: June 24, 2008, 09:42:33 am »

For those of you who have not checked out Mitch's masks, do so.  They are terrific and better yet, free.
Quote
I strongly recommend noise reduction on a layer and using a surface mask to keep noise reduction away from the edges. That will allow you to use more aggressive noise reduction settings in many cases without losing significant details. That can make it less likely for noise to reemerge after capture sharpening. I have a free script that can automate the generation of surface masks. There are even options to limit the masks to tonal/color ranges (e.g., the shadows).

It takes more work, but if you can restrict noise reduction to just the features where it's most needed, like the shadows, you can be more aggressive with the noise reduction settings. Restricting noise reduction was the #1 motivation behind my masking script.

http://www.thelightsright.com/TLRProfessionalMaskToolkit.htm


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Mark D Segal

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« Reply #30 on: June 24, 2008, 11:47:11 am »

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I'm not surprised.

Noise reduction software doesn't remove noise. It makes it less obvious. It can be accomplished in a number of ways, but the essence is the reverse of sharpening. Neighboring pixels are examined to determine whether the values for a pixel are significantly different *WHERE* little variation is expected in terms of color and/or luminosity. The contrast between those pixels and their neighbors is reduced.

The Median filter, for example, is a fairly blunt tool for noise reduction. The neigboring pixels are consulted and their median value (sort the values and take the middle value) is used to adjust the pixel. This "smooths out" variation and reduces noise.

Sophisticated tools like NeatImage, Noise Ninja, and Noiseware have more sophisticated algorithms for determining noisy pixels and for replacing their values, but in essence they reduce contrast between noisy pixels and their neighbors.

Sharpening software can still detect the contrast between noisy pixels and their neighbors *AND* emphasize the contrast, undoing some/all of the noise reduction.

That's why I refer to noise reduction and capture sharpening as antagonistic in my eBook and my video on sharpening.

http://www.thelightsright.com/SharpeningYourPhotographs.html

You can reduce noise to the point where capture sharpening cannot make it more visible. The resulting artifacts -- a plastic-like appearance from loss of significant details -- will likely be worse than some residual noise.

If you do not use layers masks, capture sharpening and noise reduction will largely cancel out. Depending which is more aggressive in effect, you will either end up sharpening noise or softening significant details.

Capture sharpening is best done with a layer mask that restricts sharpening to the edges. ACR and LR now include some edge masking. Focal Blade and Photokit Sharpener give you direct control over edge masking. So do my actions and scripts (there are free actions and scripts for noise reduction, masking, and sharpening on my site).

I strongly recommend noise reduction on a layer and using a surface mask to keep noise reduction away from the edges. That will allow you to use more aggressive noise reduction settings in many cases without losing significant details. That can make it less likely for noise to reemerge after capture sharpening. I have a free script that can automate the generation of surface masks. There are even options to limit the masks to tonal/color ranges (e.g., the shadows).

It takes more work, but if you can restrict noise reduction to just the features where it's most needed, like the shadows, you can be more aggressive with the noise reduction settings. Restricting noise reduction was the #1 motivation behind my masking script.

http://www.thelightsright.com/TLRProfessionalMaskToolkit.htm

Enjoy!

Mitch
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Hi Mitch,

Yes, this is all very much to the point. I always use PK Sharpener, and most of the time I confine noise reduction to the areas of an image where it shows most by using a layer and layer mask. One then also has the added freedom of playing with opacities to get the right blend between sharpening and noise reduction in the event of areas where some compromise is inevitable. More often than not, given where noise usually shows most, it is not. Thanks for the reference to your toolkit.

Mark
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bjanes

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« Reply #31 on: June 24, 2008, 06:02:46 pm »

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Bill, realizing that ACR sharpening prior to noise reduction is not your recommendation, could you process the same image with modest ACR "capture" sharpening followed by Noiseware default?
[a href=\"index.php?act=findpost&pid=203123\"][{POST_SNAPBACK}][/a]


This is what you requested on the left. The image with NR in Noiseware and then capture sharpening in PK (the same image as previously shown) is on the right. IMHO, the ACR sharpened image followed by Noiseware has less edge noise, possibly because of differences in masking or sharpening settings, than other image.

Optimum results would probably involve NR with Noiseware using a layer and surface mask followed by sharpening on a layer with an edge mask.

Bill

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gmitchel

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« Reply #32 on: June 24, 2008, 06:51:24 pm »

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Thanks for the reference to your toolkit.
[a href=\"index.php?act=findpost&pid=203372\"][{POST_SNAPBACK}][/a]

I hope the mask toolkit helps. I always use a surface mask for noise reduction. Then I can grab a brush filled with black at something like 20% opacity and further adjust the mask so that noise reduction is applied where it's most needed. Shadows or gradients for sky or water, mostly.

The surface mask is not just an inverted edge mask, BTW. That could make for some artifacting. The surface mask has a bit more Gaussian Blur applied.

Cheers,

Mitch
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Gordon Buck

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« Reply #33 on: June 24, 2008, 09:40:30 pm »

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This is what you requested on the left. ... [a href=\"index.php?act=findpost&pid=203455\"][{POST_SNAPBACK}][/a]

Thanks, Bill.  You have a finer and more critical eye than I.  I'd say those two treatments produce essentially the same result.  That being the case, I'd stay with the ACR sharpening followed by Noiseware.  But I suspect you are correct about the optimum; I'm certainly still seeking that optimum.

How do you work with Noiseware for distant detail like leaves in trees?  I see that there is a landscape setting and note the differences in the various sliders.  It seems to me that noise reduction for distant detail is likely to be a different layer with very light settings, especially for luminance.
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Mark D Segal

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« Reply #34 on: June 24, 2008, 11:38:27 pm »

Quote
This is what you requested on the left. The image with NR in Noiseware and then capture sharpening in PK (the same image as previously shown) is on the right. IMHO, the ACR sharpened image followed by Noiseware has less edge noise, possibly because of differences in masking or sharpening settings, than other image.

Optimum results would probably involve NR with Noiseware using a layer and surface mask followed by sharpening on a layer with an edge mask.

Bill


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Bill,

from what I see, both images are artifacted, but in different ways, and I'd be really hard-pressed to say which I prefer, because they're both kind of.......OK you get the point.

Over the past few days I did a bunch of grandchildren pics - shot them at ISO 1600 with the 1Ds3 because I wanted to further explore the question of noise on skin at high ISO with reasonably correct exposures. The camera really takes specular highlights seriously so I had to force it to be "wrong" with at least 1 stop of positive EC, which took me into a reasonable range of ETTR-land (still needed about half a stop of Exposure adjustment in ACR, and some Brightness). At 50% magnification on display the noise is really slight, but shows more at 100%. It's  a fine-grain effect. Noiseware shows it as low level high-frequency noise ranging from about 5 in the highlights to 10~12 in the shadows. I ran default Noiseware on the skin only, avoiding eyes and lips. Then I ran default PK Capture for High Res Digital at Superfine. It really didn't bring the noise back. With all this stuff on layers I can switch anything on and off in any sequence, which I've done, and I've observed that the combination of NW and PK works well. So this story is obviously very specific to the kind and amount of noise one is dealing with, hence to an extent camera-specific.
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Panopeeper

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« Reply #35 on: June 24, 2008, 11:59:03 pm »

Bill,

questions regarding the sample you posted above:

1. do the yellow blotches appear in Nikon Capture as well?

2. which step/action gets rid of them in ACR?
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« Reply #36 on: June 25, 2008, 08:59:49 am »

Quote
Bill,

questions regarding the sample you posted above:

1. do the yellow blotches appear in Nikon Capture as well?

2. which step/action gets rid of them in ACR?
[a href=\"index.php?act=findpost&pid=203495\"][{POST_SNAPBACK}][/a]

Gabor,

Yes, the yellow blotches do appear in Nikon Capture conversions, but to a lesser extent. These blotches appear where there are dark areas in the blue channel, which makes sense since yellow is the complement of blue.

With all sharpening and noise reduction turned off in both programs, the noise pattern between the two programs is quite different. The grain pattern in NC is tighter, more prominent, and uniform. In ACR setting the default color NR is 25, and this results in a more blotchy appearance in the blue channel and increased yellow blotches. Setting color NR to zero in ACR makes the pattern more uniform, but the high frequency noise is markedly increased.

For illustration, Nikon Capture NX is on the left and ACR with color NR= 0 and luminance NR = 0 is on the right:

[attachment=7211:attachment]


This view demonstrates the blue channel of ACR with ACR color NR = 0, luminance NR = 0 on the left and ACR with the default color NR = 25 on the right.

[attachment=7212:attachment]

Finally, here are the Noiseware profiles. NC is on the left (ignore CR 25 in the title), and ACR with color NR = 25 in the middle and ACR with color NR = 0 on the right.

[attachment=7213:attachment]

From this limited testing, Nikon Capture NX has better noise characteristics with the test image and the results with Noiseware NR are better with the NC image (not illustrated).
« Last Edit: June 25, 2008, 09:12:40 am by bjanes »
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Mark D Segal

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« Reply #37 on: June 25, 2008, 09:17:23 am »

Bill,

Thanks for taking the trouble to do this. Regarding the top row of illustrations, I guess it depends on whether you prefer Pointillisme or Fauvisme as a style of photographic art.  

For the second row - how do you capture a blue channel in ACR, which has no channels palette - did you get at it with Rawnalyze or another piece of software?

The Noiseware profiles are on the whole pretty ugly, with a couple of exceptions. I think all this raises a real question about whether beyond a certain level of noise -  any of these tools can really do a good job of rescuing the image while preserving wanted detail.
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bjanes

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« Reply #38 on: June 25, 2008, 09:44:30 am »

Quote
Bill,

Thanks for taking the trouble to do this. Regarding the top row of illustrations, I guess it depends on whether you prefer Pointillisme or Fauvisme as a style of photographic art.   

For the second row - how do you capture a blue channel in ACR, which has no channels palette - did you get at it with Rawnalyze or another piece of software?

The Noiseware profiles are on the whole pretty ugly, with a couple of exceptions. I think all this raises a real question about whether beyond a certain level of noise -  any of these tools can really do a good job of rescuing the image while preserving wanted detail.
[a href=\"index.php?act=findpost&pid=203562\"][{POST_SNAPBACK}][/a]

Mark,

For the blue channel I rendered the files with ACR into Photoshop, and got the blue channel from there.

I think you are correct in stating that the noise in this image is too high to be rescued by any type of NR. The exposure correction was +1.75 EV for this image. With proper ETTR at ISO 1600, the results are much better with the D200, but this camera has too much noise for good high ISO shooting.

Bill
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Panopeeper

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« Reply #39 on: June 25, 2008, 10:47:58 am »

Quote
Yes, the yellow blotches do appear in Nikon Capture conversions, but to a lesser extent. These blotches appear where there are dark areas in the blue channel, which makes sense since yellow is the complement of blue.
Bill,

do you mind uploading the raw of this demo?

Thanks
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