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12-10-2014, 07:08 PM - 4 Likes   #1
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K-3 High ISO Noise Reduction and Loss of Detail (With Pictures!!)

There was a recent thread regarding user disappointment with actually getting sharp results from their K-3. One of the early responses included a video featuring the famous (and verbose) "Ed" from photouniverse. In it, Ed proposes that he could not get sharp photos at ISO 800 to 1600 without turning off the High ISO Noise Reduction feature on his camera. He feels that the noise reduction is overly aggressive at moderately high ISOs and that results in avoidable blurring.


If you want to save quite a bit of time, he gets to his point just beyond the 10 minute mark.

That sounded strange to me for two reasons: 1) I had my doubts that noise reduction was being applied for non-JPEG files and 2) I was was not sure that such would appear as easily discernible softness. OTOH, Why would Ed fib about such a thing?

It being a very dark and gray day and me being quite bored with nothing particularly useful to do, I decided to put the notion to test.

Exposure and Processing:
  • Firmware v1.11
  • RAW capture (DNG)
  • Av mode at f/5.6 with +1 exposure compensation
  • Import into Lightroom with Adobe Standard settings for Pentax K-3
  • Direct adjustment in Lightroom of both color and luminance noise reduction to make for minimum correction while maintaining maximum detail
  • LaCA correction was applied to all captures
  • Aside from the above, no other adjustments were made in PP
  • Comparisons were done at full (24 Mpx) resolution from screen captures directly from Lightroom's comparison feature
  • NR status was confirmed by examination of the source DNG exif

The Setup:
  • K-3 on tripod mounted to Pentax-FA 35/2
  • Subject is some stuff on my small kitchen table with natural gray-grim illumination
  • Subject chosen for mix of detailed middle-tones and dark tones as well as a few strategically-placed coffee grounds

This is the ISO 200 image used as the baseline for the comparisons.



Focus was at the right margin of the white napkins (serviettes). The following photos are full-resolution (24 Mpx) crops from the dark areas of the napkin holder, the face of the napkin, and the coffee grounds at right on the table top.

ISO 1600 Comparison
Ed at photouniverse claims significant detail loss at both ISO 800 and ISO 1600. The exif from shots I did at ISO 1600 did indeed indicate that "weak" NR is applied at that ISO, so it was with some interest that I examined the results:

Here are the crops from the base of the napkin holder:

Auto NR ON


Auto NR OFF


Here are the crops from the face of the napkin:

Auto NR ON


Auto NR OFF


And here are the crops of the coffee grounds:

Auto NR ON


Auto NR OFF


There is an obvious loss of detail moving from ISO 200 to ISO 1600 in both cases, with very slight, if any difference between having NR turned off and NR turned on.

At this point it would be good to compare the NR applied in Lightroom to normalize the appearance:

Base image:
Color = 7
Luminence = 7
Auto NR On
Color = 20
Luminence = 29
Auto NR Off
Color = 20
Luminence = 27
As you can see, the amount of correction in PP was essentially the same for both cases indicating that the amount of correction applied in-camera was relatively small. To confirm, here are both images with no NR applied by Lightroom. The Auto NR Off exposure is to the right:


Auto NR Off to the right.

The image with Auto NR Off is only slightly noisier than the version with weak correction applied in-camera.

ISO 6400 Comparison

Having done the comparison at moderately high ISO, it seemed good to me to see what it looks like at ISO 6400, the upper limit I have set for auto ISO on my K-3. As with the ISO 1600 images, Auto NR was active when turned on with "weak" correction applied. Here is the same series as above:

Here are the crops from the base of the napkin holder:

Auto NR ON


Auto NR OFF


Here are the crops from the face of the napkin:

Auto NR ON


Auto NR OFF


And here are the crops of the coffee grounds:

Auto NR ON


Auto NR OFF


The detail loss at ISO 6400 is fairly severe with somewhat more being present when the in-camera NR was used. Turn the NR off and you get a little less artifact in the napkin and a little more coffee dust on the table.

As before, here is the amount of correction applied in Lightroom:

Base image:
Color = 7
Luminence = 7
Auto NR On
Color = 20
Luminence = 48
Auto NR Off
Color = 17
Luminence = 48
Yes, the Auto NR capture required a little more color noise correction. Go figure.

As before, here is the comparison of both images with no NR correction applied by Lightroom. The Auto NR Off image is on the right.



As you can see, the NR off image has significantly more noise than that where NR was applied in-camera.

Summary

If you made it this far, you must be made of strong stuff, either that or you decided to skip the dull stuff and cut to the chase. Here are the bullet points:
  • High ISO Auto NR is applied to RAW images and the results of that noise reduction are visible in Lightroom on import
  • When additional specific NR (beyond the import defaults) is applied in Lightroom, there is little difference in retained detail at ISO 1600. There is some difference in artifact with the benefit going to having Auto NR turned off.
  • At ISO 6400, the amount of noise removed in-camera was more significant, but again there was little difference in loss of detail with most of that being due to artifact generated by the in-camera NR.
I found little evidence that turning Hi ISO Auto NR off increases capture detail on My K-3. Why my results were at odds with Ed at photouniverse is anybody's guess. It may be that my lens was inadequate to see any real difference. It may also be that he was shooting with light that was higher quality allowing for more detail to start with. (A good example would be the daylight shadow test used in the K-3 detailed review on this site.) I intentionally did my test in crud light to decrease the contrast and base detail.


Steve


Last edited by stevebrot; 12-11-2014 at 05:54 PM.
12-10-2014, 07:21 PM   #2
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Thanks for the examples Steve, very interesting.
12-10-2014, 07:28 PM   #3
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I've got the same upper ISO limit set on my K-3 as well. Always wondered what I should do w/ Auto NR - set it on or off - I've left it on as I didn't think it'd make a difference in post. Apparently my strategy to use the PF "recommended" setting here has been vindicated!
12-10-2014, 07:33 PM   #4
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Thanks for sharing your study and results, Steve, I too was a little hesitant and puzzled with Ed's comment on mid-high ISO noise reduction. My k-3 is relatively new, so may be it was a slight problem only in the early production cycle. I don't find softness at least not yet. For now, I switch from auto NR to slightest NR for high ISO; and see how it goes.

12-10-2014, 07:44 PM   #5
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Original Poster
QuoteOriginally posted by slipdm16 Quote
Always wondered what I should do w/ Auto NR - set it on or off
QuoteOriginally posted by aleonx3 Quote
Thanks for sharing your study and results, Steve, I too was a little hesitant and puzzled with Ed's comment on mid-high ISO noise reduction.
I am not changing my settings at present, though I may do some additional testing at some point. What was a real eye-opener to me was what could be done in Lightroom. I typically shoot at low ISO and don't worry about noise reduction. It was a real eye-opener to see that the Lightroom defaults for color noise are an overkill for the most part and that the luminence values are inadequate for the K-3.


Steve
12-10-2014, 07:52 PM   #6
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QuoteOriginally posted by stevebrot Quote
I am not changing my settings at present, though I may do some additional testing at some point. What was a real eye-opener to me was what could be done in Lightroom. I typically shoot at low ISO and don't worry about noise reduction. It was a real eye-opener to see that the Lightroom defaults for color noise are an overkill for the most part and that the luminence values are inadequate for the K-3.


Steve
I usually turn off color noise but only apply slight luminance in LR for k-5/IIS, now that I have took closer look for k-3.
12-10-2014, 08:03 PM   #7
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I tried this a few days ago, turned off auto NR, took K3 to State Park, used tripod most of the time, it was cloudy and hazy, and even worse in the heavily wooded areas. Result was that turning it off didn't seem to make that much difference to me. It was not the best conditions, some of the photos show grain. I took some nice photos and I like grain anyway. My aunts point and shoot couldn't even focus in the darker areas of the park. She stated, "Your camera is still focusing in the dim light?"
12-10-2014, 08:08 PM   #8
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Why does everyone seem to hate the ISO 12233 test chart?

12-10-2014, 10:39 PM   #9
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Its been quite a while since I looked at this but I recall that, from other peoples testing, that the amount of blurring was very much dependant on the scene being captured. Don't know if anything has changed with with one of the firmware versions since then though.
12-10-2014, 11:39 PM   #10
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QuoteOriginally posted by rawr Quote
Why does everyone seem to hate the ISO 12233 test chart?
Can't hate what I don't have*. Are you volunteering to do the study?


Steve


* Recently deprecated. The new standard is ISO 12233:2014...new chart, new methods...
12-11-2014, 01:57 AM   #11
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Can it be that Pentax adjusted the auto NR behavior in the latest firmware?
12-11-2014, 08:21 AM   #12
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QuoteOriginally posted by GrinMode Quote
Can it be that Pentax adjusted the auto NR behavior in the latest firmware?
That may very well be.

In the mean time, there are third and fourth options.

3. Set the NR to always be the same using the camera menu

4. Create a custom Auto NR profile based on a best guess of what it should be


Steve
12-11-2014, 08:36 AM   #13
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Steve, thanks for putting this together. Please tell me if I'm understanding your conclusion correctly. Your tests are confirming High ISO NR really is a JPEG-only function?
12-11-2014, 12:19 PM   #14
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QuoteOriginally posted by IchabodCrane Quote
Your tests are confirming High ISO NR really is a JPEG-only function?
Not really. The High ISO NR is applied for RAW capture (documented in the exif) and does have an effect (see the noisy comparison shots). What it does not do is result in any more blurring or loss of detail as claimed by Ed at photouniverse.

That being said, it may be that excessive detail loss might be present with other subjects in stronger light. Ed (photouniverse) lives in SW Utah where the light is typically not diffuse. The light for my test was intentionally soft in order to present a worse case scenario where the amount of "signal" was intrinsically low. Likewise, my choice of subject in that light presented a situation where the potential for artifact is intrinsically high.

I did do a few in-camera JPEGs, but screwed up the comparisons and did not include them. I will see if I can salvage and post those as a comment.


Steve
12-11-2014, 01:01 PM   #15
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How About A Few JPEGS?

Here are comparison in-camera JPEGs at ISO 1600. The image on the right has Auto High ISO NR turned OFF. JPEG settings were for "natural" rendition and no PP was applied to either image.



There is obvious softness in the wood grain of the left-hand image with not much difference in noise between the two.



I would call it a draw between these two with little visible difference in rendering. I have noticed a difference in brightness with the NR corrected images being a little lighter.



There is a subtle loss of detail in the left hand image here.

Sooooo...it might be a good idea to turn off the Auto NR if you are shooting JPEG.


Steve

Last edited by stevebrot; 12-11-2014 at 04:36 PM.
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