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12-05-2013, 08:10 AM   #1
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K-3 and the red cloth

I'm sure that many on this forum are aware that Pentax DSLRs have always had problems showing detail in the bright red cloth in Imaging Resource's standard still life scene. This tends to occur at high ISOs. I have downloaded the raw file from the K-3 at ISO 6400 and find that after applying optimum noise reduction in my raw processor (Photo Ninja), the detail from the cloth is almost completely lost. (See attached screenshot of 50% enlargement below.) With the K-5II sample at ISO 6400, detail is still somewhat present.

So what is the explanation for the K-3's behavior in this situation, and is it a deal breaker?

Rob

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Last edited by robgo2; 12-05-2013 at 08:16 AM.
12-05-2013, 08:14 AM   #2
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Hey there!

I am sorry I don't know the red cloth thing, I have a different quesiton, I remember this background setup. I have seen videos on youtube of iso noise and color match side by side between Pentax cameras and other cameras, are you the same person?

If yes hats off to you man and its nice to meet you here

Cheers!
12-05-2013, 08:18 AM   #3
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The k3 has more noise, that should help explain it.

Adam
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12-05-2013, 08:23 AM - 2 Likes   #4
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QuoteOriginally posted by robgo2 Quote
I'm sure that many on this forum are aware that Pentax DSLRs have always had problems showing detail in the bright red cloth in Imaging Resource's standard still life scene. This tends to occur at high ISOs. I have downloaded the raw file from the K-3 at ISO 6400 and find that after applying optimum noise reduction in my raw processor (Photo Ninja), the detail from the cloth is almost completely lost. (See attached screenshot of 50% enlargement below.) With the K-5II sample at ISO 6400, detail is still somewhat present.

So what is the explanation for the K-3's behavior in this situation, and is it a deal breaker?

Rob
LOL.

Yes, it's a deal breaker since all I *do* is go into dark and dimly lit JoAnn fabrics stores (sometimes after they close for the night) and take my slowest lenses - so I have to use a high ISO - and find flat contour-less fabric samples so that I can print from a 50% enlargement.



12-05-2013, 08:32 AM   #5
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QuoteOriginally posted by LaurenOE Quote
I *do* is go into dark and dimly lit JoAnn fabrics stores (sometimes after they close for the night) and take my slowest lenses - so I have to use a high ISO - and find flat contour-less fabric samples so that I can print from a 50% enlargement
Now that's what I call a proper camera test, no brick wall nonsense for you then.
12-05-2013, 08:37 AM   #6
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k-5IIs: http://farm4.staticflickr.com/3751/10583794264_dd23b3318d_o.jpg
k-3: http://farm8.staticflickr.com/7420/10583764306_c6333f199b_o.jpg

I wouldn't say the k-5 does better. It's just smaller, giving the illusion that the detail isn't lost.

That being said:

D7100: http://farm3.staticflickr.com/2871/10584008073_74ea48c12c_o.jpg
D600: http://farm8.staticflickr.com/7388/10583745535_94e215ee3b_o.jpg

The D7100 doesn't fare so well in that red cloth either. The D600 does nicely.
All shots were taken from the ISO 6400 RAW files on IR, and processed to practically the same NR levels in Lightroom 5.
12-05-2013, 08:40 AM   #7
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I always thought detail in red and black were the hardest things for digital sensors to capture.
12-05-2013, 08:40 AM   #8
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QuoteOriginally posted by Deedee Quote
Hey there!

I am sorry I don't know the red cloth thing, I have a different quesiton, I remember this background setup. I have seen videos on youtube of iso noise and color match side by side between Pentax cameras and other cameras, are you the same person?

If yes hats off to you man and its nice to meet you here

Cheers!
Definitely not me. I may be obsessive, but not that obsessive.

Rob

12-05-2013, 08:56 AM   #9
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In all cameras other things suffer at ISO 6400 too. If you have to shoot at ISO 6400+ to get the shot, then lets hope your image does not depend on noise, DR, color fidelity, etc to make it work.
12-05-2013, 09:14 AM   #10
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QuoteOriginally posted by Adam Quote
The k3 has more noise, that should help explain it.
Adam,

In IR's own write-up, the K-3 does worse with the red cloth than the NEX 7 and the D7100, which have similar sensors, so I don't think that it is simply a matter of more noise. The editors pointedly comment on Pentax's history of poor rendering of detail in reds.

I have done some more experimenting with my raw convertor, and I believe that the problem lies with the color noise reduction. Noise Ninja 4 (inside Photo Ninja) has the default color NR set at a value of 50. If I set it to 0, some detail in the cloth is restored, along with tons of chroma noise. If I set it to 18, I lose more detail,and almost all of the chroma noise vanishes. ACR seems to handle the red chroma noise a bit better. This is one of the few cases in which ACR outperforms Photo Ninja, although I have not seen the same advantage with my K-5 or K-5II.

Below are the IR samples from Photo Ninja/Noise Ninja 4 with color noise at 0 and 18.

Edit: I forgot that luminance NR was turned off in ACR. If I add luminance NR equal to that in Noise Ninja, there is only minimal difference in the red cloth and less detail everywhere else. On balance, Photo Ninja/Noise Ninja is definitely superior.

Rob
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Last edited by robgo2; 12-05-2013 at 09:20 AM.
12-05-2013, 09:27 AM   #11
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This was definitely the deal breaker for me. It showed that, regardless of manufacturer, APS-C had reached its limit and I wasn't going to achieve with the K-3 what I wasn't already achieving with the K-5IIs. Made no sense to upgrade, not for what I shoot.
12-05-2013, 10:04 AM - 1 Like   #12
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QuoteOriginally posted by Parry Quote
This was definitely the deal breaker for me. It showed that, regardless of manufacturer, APS-C had reached its limit and I wasn't going to achieve with the K-3 what I wasn't already achieving with the K-5IIs. Made no sense to upgrade, not for what I shoot.
Ummm, no. It all depends on how much "grit" you can tolerate in your ISO6400 images. Here is my attempt at the red swatch with darktable v1.2.3. Only enough chroma and luma NR to get rid of the color blotching. Pumped up the local contrast detail a bit. Still detail there. I have the IIs and the K-3 runs rings around it in resolution.

Jack
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12-05-2013, 10:12 AM   #13
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QuoteOriginally posted by jbinpg Quote
Ummm, no. It all depends on how much "grit" you can tolerate in your ISO6400 images. Here is my attempt at the red swatch with darktable v1.2.3. Only enough chroma and luma NR to get rid of the color blotching. Pumped up the local contrast detail a bit. Still detail there. I have the IIs and the K-3 runs rings around it in resolution.

Jack
Ummm, yes. Actually.

But there we go.
12-05-2013, 10:17 AM - 1 Like   #14
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Didn't we have this thread very recently? Here is what that thread came up with:
a) Red's are the toughest colours for CMOS Bayer sensors (regardless of FF or crop, its just the way it deals with wavelengths and interpolation)
b) Red is a special colour in the way our eyes gather it and how we understand it (how we imagine it, what it means to us culturally), so we are most likely to notice something being "off" with it. A lot of people also sense red differently (some degree of "colour blindness" I guess)
c) Most of this can be fixed if you use things like camera calibration (or colour passport) and post-process the image correctly on a calibrated monitor. White balance, exposure, contrast all have a huge impact on the "reds." A green plant will still be "understood" to be green by the viewer, even if the white balance is too warm or cold. But a red stop sign will look really weird if the WB is off - suddenly it will be pink or orange instead of the stop sign red that I love so much and know exactly what it should look like. The viewer might demand his expectation of "red" be obeyed much more than his expectation of other, more common colours.
d) This isn't even an issue in most photography, because pure red is actually a rare colour. (which is also the reason why the sensors are generally weak at reds and better at blue and green)

Someone even posted examples of slightly processed files that brought out all the detail in the reds (on a flower or cloth, I dont remember exactly), even though initially it looked oversaturated/empty. I really doubt that the K-3 is just "missing" something and that another camera in its price range would be substantially better. Only way to get more detail is to have significantly higher bitrate and newer/better sensor. The only way to show all of it, is to process/interpret the raw data in that way. But hey, if you don't think so, maybe a Foveon sensor will do the trick. Or a MF CCD sensor. Be sure to share your findings if you go for it.

Last edited by Na Horuk; 12-05-2013 at 10:29 AM.
12-05-2013, 10:32 AM   #15
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There is a balance between red and blue. Some camera are more blue oriented, other are more red oriented. But is also a problem of lights and settings used on Imaging Resource tests. On DPReview, in the past, with K-5, and K-5 II, red fabric are more detailed. I do not see test photo with K-3 on DPR yet.

I also made some PP with that red cloth and noise, with RawTherapee. And maybe, in the future I will try some more. You can see it here:

https://www.pentaxforums.com/forums/172-pentax-k-3/242034-image-resource-k3-v...ml#post2572618
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