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02-17-2010, 11:26 PM   #1
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Is there anything to these K-X comparison shots?

In the middle of this (link) page...
Pentax K-X - The Photo Forum - Photography Discussion Forum
.... are some comparison photos.

Valid? Too unscientific/uncontrolled? Any merit to the comment....
QuoteQuote:
Check out the complete loss of detail in the red pattern. I'm guessing they're doing some SERIOUS in camera NR to kill the red channel like that. You can see the color shift in the pink as well.
I'm kind of exhaustively checking out this camera's reputation before I commit. It's likely to be my one and only for a very long time.

02-18-2010, 12:38 AM   #2
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I cant say...

I know my early tests with it at ISO 6400 and 3200 left me smiling. But in my real world shooting I have not shot a lot of 100% crops of fushia fabric. But I would be a bit put off by those test shots myself, although I can believe that at ISO 1600 there is 'that' much NR going on with the K-x.

Iso 6400






ISO 3200
02-18-2010, 02:08 AM   #3
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At this point I might as well mention the K-x thread I started here in October, when I too was a new K-x owner.

Lots of good reds in the images there:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/77254-new-k-x-owne...le-images.html
02-18-2010, 07:09 AM   #4
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The guy posting that can't tell the difference between a colour response shift and NR obscuring the detail. The pink is the clue here, if it was NR there wouldn't be a colour shift in the pink.

The detail's clearly there, it's just partially hidden because the K-x is rendering the two Red's closer together than the D90 is.

02-18-2010, 08:35 AM   #5
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Those samples might have been done with pre-production models. They might not be fully representative of what is going on right now. Don't forget they were done around the time the K-X was introduced, so it is a possibility.
02-18-2010, 09:21 AM   #6
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Shoot in RAW and don't worry about it. ;-) Learning to properly process RAW files makes you look at a camera in a whole new light... and "excessive NR" will be entirely up to you.
02-18-2010, 09:45 AM   #7
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Probably owing to my skills both with the camera and manually processing the raw files, but I'm not sure my results have been as stunning as those from Gus. Nevertheless, they have greatly exceeded my expectations. Perhaps if we looked at any of these at 100% crops, we'd find fault, but ISO 3200 never looked as good to me as what I get from my K-x in normal size viewing. FA77ltd 1/30 at F/2.8 ISO 3200.
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02-18-2010, 03:45 PM   #8
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QuoteOriginally posted by frascati Quote
Valid? Too unscientific/uncontrolled?
it was a controlled test of some aspects of camera performance, but was never intended to test what the person commenting on it saw. There is no guarantee the focus is at the same place, no guarantee the white ba;ance was chosen to optimize the texture there, etc. And if the other camera happened to render that part of the picture better, the K-x would render a different better. there's basically no IQ differences to speak of between these cameras (and indeed, hardly any differences in practice between *any* two DSLR's - the lenses and photographer are both far bigger determinants).

02-18-2010, 04:01 PM   #9
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Red is the most "difficult" color in JPG compression -
this was also brought up for the K7 in:

Why can't the K7 render these details?

The first thing we should note is that the K7 by reputation uses less noise reduction than most other dSLRs -
hence the reputation of noisier high ISO images,
so it has to be the current way Pentax are doing noise reduction.

However all other dSLR also suffer from this to a greater or lesser degree -
and the most surprising was that I found the Pentax K20 did much better than most other dSLRs

If details in red are important, I believe the short answer is to either turn noise reduction Off, or to process RAW.
02-18-2010, 04:29 PM   #10
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The shots Gus posted don't show smearing of the red details, so it is not clear what Imaging Resource did to process their test shots differently. I would also join in wondering why there is NR on ISO 1600 at all. I shoot raw, and I usually apply no NR or very little to ISO 1600 from the K-x. Noise Ninja usually profiles the K-x 1600 shots at 16 or less, which is little noise. The Canon shots at 1600 look more like what I am used to seeing from raw files from the K-x.
02-18-2010, 05:15 PM   #11
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QuoteOriginally posted by GeneV Quote
The shots Gus posted don't show smearing of the red details, so it is not clear what Imaging Resource did to process their test shots differently. I would also join in wondering why there is NR on ISO 1600 at all. I shoot raw, and I usually apply no NR or very little to ISO 1600 from the K-x. Noise Ninja usually profiles the K-x 1600 shots at 16 or less, which is little noise. The Canon shots at 1600 look more like what I am used to seeing from raw files from the K-x.
Not quite, look at his last shot of the girl in the red sweater - even though the sweater is not quite in focus - it should not lose so much detail - also the threads on the baseball look carefully they lack good internal detail - then there's the Coke can - see the mottling in the red logo? (the last is JPG compression of red).
(It should be noted this NOT a criticism of Gus's photos - it's just that fine details withIN red are what we're looking for)

So it's not Imaging-Resource - it's Pentax's noise reduction and regular JPG compression.
Although the area shown may seem "significant" - it is at the pixel peeping level of 100%

The same ISO1600 shot with Noise Reduction Off (beware this opens full sized photo at 5.5Mb) shows that the details are all there.

Similarly one can look at the K-x ISO3200 shot with Noise Reduction Off to see how well the K-x renders the detail in the red patch -
these would be quite a bit better than the comparisons of Nikon D90 and Canon 50D.

So as I said if details in red are important then shoot with Noise reduction Off or as in your case process RAW -
then the last step make sure when saving to JPG that the compression is not too high which will lose red detail -
one would be quite surprised in how high a JPG quality is needed to retain details in red in PhotoShop Elements it's around quality "9"
- then look at the resultant image before closing the image to be sure.

Last edited by UnknownVT; 02-18-2010 at 05:43 PM.
02-18-2010, 05:19 PM   #12
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I agree with this. Im not smart enough about this stuff, but theres some kind of color calibration you should go through in the processing of RAW to JPG. Its possible that the Pentax firmware isnt so good at distinguishing between those particular shades of red - but that deficiency could be overcome by third party calibrated processing (not noise reduction)

But look at the green leaves to the left. The Kx clearly stomps the canon 50D there, and the detail in the basket is better on the Kx than either the Canon and the Nikon.

We dont know how the focus was made, etc.... but I think that it makes the Kx look pretty good to me.
02-18-2010, 07:58 PM   #13
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QuoteOriginally posted by UnknownVT Quote
Not quite, look at his last shot of the girl in the red sweater - even though the sweater is not quite in focus - it should not lose so much detail - also the threads on the baseball look carefully they lack good internal detail - then there's the Coke can - see the mottling in the red logo? (the last is JPG compression of red).
(It should be noted this NOT a criticism of Gus's photos - it's just that fine details withIN red are what we're looking for)

So it's not Imaging-Resource - it's Pentax's noise reduction and regular JPG compression.
Although the area shown may seem "significant" - it is at the pixel peeping level of 100%

The same ISO1600 shot with Noise Reduction Off (beware this opens full sized photo at 5.5Mb) shows that the details are all there.

Similarly one can look at the K-x ISO3200 shot with Noise Reduction Off to see how well the K-x renders the detail in the red patch -
these would be quite a bit better than the comparisons of Nikon D90 and Canon 50D.

So as I said if details in red are important then shoot with Noise reduction Off or as in your case process RAW -
then the last step make sure when saving to JPG that the compression is not too high which will lose red detail -
one would be quite surprised in how high a JPG quality is needed to retain details in red in PhotoShop Elements it's around quality "9"
- then look at the resultant image before closing the image to be sure.
I process all my shots in Raw, so the in-camera NR is not a factor. I apply NR very sparingly.

Your eyes may be better than mine, but I'm not sure I see Gus's shots the same way you do. The depth of field is so shallow on the shot of the girl, that I couldn't make any judgments at all about the sweater, and the Coke can looks pretty good to me.
02-19-2010, 12:36 AM   #14
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QuoteOriginally posted by GeneV Quote
I process all my shots in Raw, so the in-camera NR is not a factor. I apply NR very sparingly.
This precisely why you're not troubled with losing details in red.....

QuoteOriginally posted by GeneV Quote
Your eyes may be better than mine, but I'm not sure I see Gus's shots the same way you do. The depth of field is so shallow on the shot of the girl, that I couldn't make any judgments at all about the sweater, and the Coke can looks pretty good to me.
I don't think my eyes are any better than anyone else's.

I don't disagree the depth of field is narrow in that shot - but even an out of focus image will show a little more than in the red sweater - probably if the sweater were green (where Pentax is stronger) there would have been more detail - albeit out of focus....

as for the Coke logo - one has to kind of know what to look for - look at the "C" in Cola one can see mottling - somewhat like artifacts/haloing.

Perhaps the best is if I illustrate this - scan of a typical red object -
left is saved with high quality JPG (PSE=10) and the second is lower quality (PSE=4)
I also added the third JPG saved in PhotoImpact 8 (my usual editor) saved at 75% which is actually pretty good/presentable quality - but as one can see in the third crop PI's JPG engine is not particularly good in preserving Red details - this is kind of similar to what Pentax are doing now with their noise reduction



Hopefully when they are shown side-by-side the mottling becomes obvious?

Where Pentax's current noise reduction strategy is weakest is retaining internal details in red.
If you care to look at the thread I linked this also applies to the K7.

But like I said if one turns noise reduction Off then the problem goes away -
but then I have already said that (sorry for the repetition).

Last edited by UnknownVT; 02-19-2010 at 11:51 AM.
02-19-2010, 06:48 AM   #15
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I don't drink much Coke so the Swiss Army Knife comparison helps.

How can one tell if the problem is with NR or the jpeg engine or both?

The beauty of the K-x to me is that at 1600, shots are amazingly clean right off the sensor. It is too bad if the jpeg engine mucks it up.
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