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02-24-2009, 01:31 PM   #1
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Pls help me understand noise in K100D vs K20D!

I have this question in my mind after seeing different results from photos taken using both cameras with FA* 80-200/2.8

The blurred background from K100D pictures show very smooth with almost no noise while the ones from K20D shows more noise.

In LR2, I have to reduce the noise for K20D shots with this lens (both color 100% and luminance 50%).

Is the CMOS sensor in K20D more sensitive to noise compared to CCD sensor in K100D?

For example, I use similar setting like this 1/2000, f/2.8, ISO 800 and I also turn on the NR on K20D to strongest level.
Shots from ISO 200 and 400 also show similar situation.

Is this normal or do I miss something in setting up my K20D?

02-24-2009, 02:43 PM   #2
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This is the penalty for cramming 8 milliopn more pixels onto the same bit of silicon.

There is no free lunch I am afraid. I use a K100D and recently tried a D80 nikon, good god the noise is just horrific.
02-24-2009, 03:25 PM   #3
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QuoteOriginally posted by Alfisti Quote
This is the penalty for cramming 8 milliopn more pixels onto the same bit of silicon.
There is no free lunch I am afraid.
Agree with that -
viewing at the pixel level.

However bear in mind most will resize the photo for display on a screen-
and when printing one does not print at the pixel level.

When resizing down there is some auto-corrolation going on which results in lower noise - so the K20D would benefit more when resizing down to the same smaller size than the K100D - theoretically there should be about 2.41x advantage in noise reduction when resizing to the same smaller size.

Similarly when printing (200ppi or better for quality) in theory there should be a 2.41X adavantage to the K20D due to coorolation (=noise cancellation).

So the K20D can afford to have 2.41x more noise, because it has 2.41x more pixels to play with.
02-24-2009, 03:35 PM   #4
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QuoteOriginally posted by UnknownVT Quote
Agree with that -
viewing at the pixel level.

However bear in mind most will resize the photo for display on a screen-
and when printing one does not print at the pixel level.

When resizing down there is some auto-corrolation going on which results in lower noise - so the K20D would benefit more when resizing down to the same smaller size than the K100D - theoretically there should be about 2.41x advantage in noise reduction when resizing to the same smaller size.

Similarly when printing (200ppi or better for quality) in theory there should be a 2.41X adavantage to the K20D due to coorolation (=noise cancellation).

So the K20D can afford to have 2.41x more noise, because it has 2.41x more pixels to play with.
Yes, it's apparent when I view 1:1 ratio.

It's a good idea, maybe I should try to print on paper and compare them.

So are you saying that I don't need to apply LR2 noise reduction? and as long as I print at the same size, the pictures should be comparable?

Thanks,

02-24-2009, 04:08 PM   #5
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QuoteOriginally posted by HermanLee Quote
So are you saying that I don't need to apply LR2 noise reduction? and as long as I print at the same size, the pictures should be comparable?
This is "in theory" - auto-corrolation in practice is not strictly linear - since noise is not always "random".

The K20D should in theory be able to "afford" 2.41x the number of noise pixelsdue to the corrolation cancellation of noise - when resized or printed to the same size, than the K100D.

Best bet is to try printing yourself using the ppi for the largest print you are likely to do - just print a small area on a small sheet of printing paper -
or size a crop of the photo and have it printed to 6x4 at one of the many digital print places/stations to get an idea of how much noise is really visible under close scrutiny.


Also Imaging-Resource.com has a section where they comment on print output quality in their reviews (note the max print sizes at high ISOs where noise is much more obvious at the pixel level) -

K100D -

" Print Quality
Excellent print quality, great color, good 11x14 inch prints. ISO 1600 images are soft but usable at 8x10, and ISO 3200 shots are still decent at 8x10 and quite excellent at 5x7.
<snip>
With the Pentax K100D, we were pleasantly surprised across the board. At 13x19, its prints were slightly soft, but quite good for wall or table display. At high ISO, image noise levels are held in check quite well up to the maximum of ISO 3200! We almost never say that. ISO 800 shots under daylight-balanced lighting look quite good at 11x14 and, those shot under incandescent lighting remain usable out at 8x10, where images from most cameras will start to fall apart (the very warm color balance of incandescent lighting forces the camera's already-noisy blue channel to work harder, producing higher noise.) Though they were somewhat noisy, even our severe incandescent test produced usable images up to 8x10 at ISO 1600, so long as we printed only the manual while balanced images (as we mention further up, the Auto White Balance's performance indoors with incandescent is the K100D's main shortcoming). ISO 800 images can survive the enlargement to 11x14 quite well. For a six megapixel sensor, the K100D holds its own. "

K20D

" Print Quality
Great print quality, good color, sharp 16 x 24-inch prints.

The Pentax K20D's printed output is really impressive, able to output usable 16 x 24-inch prints from both ISO 100 and 200 shots. They're slightly soft, but really quite good. ISO 200 shots print the same as 100, producing a good 16x20 or great 13x19. ISO 400 images do just fine at 13x19, both sharp and crisp at this very large size. ISO 800 shots are still quite good at 13x19, though some chroma noise begins to creep into the shadows and other dark areas. At 11x14, they're still there, but less noticeable, and detail is good. ISO 1,600 shots start to lose contrast from the greater noise overall, but still print quite well at 8x10 inches. ISO 3,200 shots are also decent at 8x10, though with more noticeable grain and continued fading in darker areas thanks to noise. Even ISO 6,400 shots are usable at 5x7, which is pretty good for such a high-resolution sensor. It's an excellent performance from the Pentax K20D. "
02-25-2009, 09:13 AM   #6
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I've turned on the NR on High ISO in K20D.
But it only says will turn on on High ISO without specifying what ISO.
What is considered as High ISO in K20D?
Is 400 considered High ISO already?

Also I noticed that if I increase the EV by +2/3 or +1,
the noise is reduced. Is this common?

Thanks,
02-25-2009, 10:43 AM   #7
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Hi Herman,

I don't have any examples handy to post, but noise on the K20D at full resolution (i.e. 4672 x 3104) seems to match the noise on the K100D at full resolution (3008x2008). Therefore I think the noise is handled better on the K20D. However, this is strongly dependent on proper exposure, and if you underexpose at all, you'll see noise in the shadows.

Also, the other thing I've seen with the K20D is that the extended dynamic range mode can give me shadow noise even at low ISOs. Others are better at minimizing it, so I'm sure there's some user error on my part.

As for when does high ISO noise reduction kick in, I don't know. That's a good question. BTW, my K20D is set for weakest NR, and that's how I was comparing to the K100D.

Bottom line, the K20D noise shouldn't be that much more (if any) than the K100D, and if you downsize the K20D shots to K100D size, the noise is better.

All of the above is my opinion, of course. I haven't done any controlled tests. See the K20D high ISO thread for lots of great examples of what's possible with the K20D.
02-25-2009, 11:00 AM   #8
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I do not have a K100 for comparisson, only a K10. From what I see and what I print, I can only say, that noise starts to be an issue with the K20 from ISO 1000 onwards, but is agreeable at ISO 1600. ISO 3200 is usable, ISO 6400 only there to get you a shot, if anything else does not work.

I usually apply a tiny amount of Luminance noise reduction in LR for ISO 1000 shots and the prints are great. Yes, there can be some graininess, depending on the colours, brightness and whether there are larger, uniform areas in the image, but generally the K20 has a very well controlled noise level.

The K20 applies only a low noise reduction level to its images, which in turn prevent details from beiong washed away as other makes do. Experience shows, that external noise reduction is always a better option and Pentax allows that, whereas in a D300 the detail is already gone before you aplly a better NR algorithm in post-processing.

Ben

02-25-2009, 11:08 AM   #9
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QuoteOriginally posted by HermanLee Quote
I've turned on the NR on High ISO in K20D.
But it only says will turn on on High ISO without specifying what ISO.
What is considered as High ISO in K20D?
Is 400 considered High ISO already?
According to dpReview's page on Pentax K20D Noise -

" Noise reduction settings
As we've seen, the K20D tends to apply very conservative levels of noise reduction by default. There are three options for increasing it, however. High ISO noise reduction can be set to Weakest, Weak and Strong, as well as the default Off setting, using option 18 in the Custom Menu setting.
Our tests show that these options have no effect below ISO 800. Their effects from ISO 800 upwards can be seen below. (It's worth noting that, although the Operating Manual states that all "Noise Reduction is set to Strong when shooting with a sensitivity of ISO 3200 or high, regardless of the setting in the Custom Menu," this doesn't appear to be true. We have only tested the results in whole stops but the settings clearly behave differently at ISO 3200). "

QuoteOriginally posted by HermanLee Quote
Also I noticed that if I increase the EV by +2/3 or +1, the noise is reduced. Is this common?
Noise normally becomes more noticable with long and under-exposures.

By over-exposing or by bringing the the darker/shadow areas more into the "normal" exposure level you are somewhat circumventing the shadows and thus reducing the noise - but that is obviously at a cost of over-exposure of the overall picture.

Also in terms of exposure - at +1 stop over-exposure - one might as well have taken the picture with the next lower ISO value and have gotten the same shutter speed/aperture combination......
02-25-2009, 07:53 PM   #10
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QuoteOriginally posted by rfortson Quote
Hi Herman,

I don't have any examples handy to post, but noise on the K20D at full resolution (i.e. 4672 x 3104) seems to match the noise on the K100D at full resolution (3008x2008). Therefore I think the noise is handled better on the K20D. However, this is strongly dependent on proper exposure, and if you underexpose at all, you'll see noise in the shadows.

Also, the other thing I've seen with the K20D is that the extended dynamic range mode can give me shadow noise even at low ISOs. Others are better at minimizing it, so I'm sure there's some user error on my part.

As for when does high ISO noise reduction kick in, I don't know. That's a good question. BTW, my K20D is set for weakest NR, and that's how I was comparing to the K100D.

Bottom line, the K20D noise shouldn't be that much more (if any) than the K100D, and if you downsize the K20D shots to K100D size, the noise is better.

All of the above is my opinion, of course. I haven't done any controlled tests. See the K20D high ISO thread for lots of great examples of what's possible with the K20D.
Hi Russ,
Yes, I think I use extended DR on K20D
I need to try the regular DR and see how it performs.
Thanks for pointing that out.
02-25-2009, 07:58 PM   #11
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QuoteOriginally posted by UnknownVT Quote
According to dpReview's page on Pentax K20D Noise -

" Noise reduction settings
As we've seen, the K20D tends to apply very conservative levels of noise reduction by default. There are three options for increasing it, however. High ISO noise reduction can be set to Weakest, Weak and Strong, as well as the default Off setting, using option 18 in the Custom Menu setting.
Our tests show that these options have no effect below ISO 800. Their effects from ISO 800 upwards can be seen below. (It's worth noting that, although the Operating Manual states that all "Noise Reduction is set to Strong when shooting with a sensitivity of ISO 3200 or high, regardless of the setting in the Custom Menu," this doesn't appear to be true. We have only tested the results in whole stops but the settings clearly behave differently at ISO 3200). "
Thanks. If that's the case then K20D should start considering High ISO at 800 & up.


QuoteQuote:
Noise normally becomes more noticable with long and under-exposures.

By over-exposing or by bringing the the darker/shadow areas more into the "normal" exposure level you are somewhat circumventing the shadows and thus reducing the noise - but that is obviously at a cost of over-exposure of the overall picture.

Also in terms of exposure - at +1 stop over-exposure - one might as well have taken the picture with the next lower ISO value and have gotten the same shutter speed/aperture combination......
That's so true. And I want to bring that shadow out
So how can I bring the shadow out with less noise.
Is NR on external software like LR is the only way right now?
02-25-2009, 08:19 PM   #12
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not much to add, excellent responses (at times like this i remember why i would rather be a pentax user, if all else was equal: it seems our kind is smarter :-P )

noise is actually all about signal to noise ratio, this is not a term specific to digital imaging actaully (and, as it ahppens, it occurs at the purely analogue stage of image capture, as a fun fact, or at least most of it does: when the signal is amplified).

because of the linear nature of "digital" image sensors, noise will always come up first in dark areas (less usefull signal), a good explanation of that is found here:
Expose Right

this is only if you are looking to understand more about the nature of noise, predict when it will appear and perhaps avoid it, with any digital camera. for the k20d specifics, i guess it is already clear:

-pixel-to-pixel is not relevant, print or simulate printing at the maximum size relevant to you, to decide what is acceptable and what not (aka: comparing noise from a 6MP sensor to noise from a 14MP sensor, for practical purposes, is irrelevant, it may be rellevant for engineering/measurebating purposes)
-k20d in my experience does better than anything else i have used (d50, k100d, gx10(k10d), some p&s but they don't count), even pixel to pixel (except maybe k100d where they are close), so it does great for practical purposes.
-it is known the extended dr on k20d causes some additional noise in the shadows (though nothing to worry about, from what i have seen)
-if utmost quality and noise control is important to you, shoot raw, disable in-camera-nr, use a good post processing nr method (i occasionally used some wavelet based nr available within ufraw, my raw converter, i was quite amazed at how well it does; others will have more extensive advice on the topic)
02-26-2009, 02:36 AM   #13
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QuoteOriginally posted by HermanLee Quote
Thanks. If that's the case then K20D should start considering High ISO at 800 & up.

That's so true. And I want to bring that shadow out
So how can I bring the shadow out with less noise.
Is NR on external software like LR is the only way right now?
You will not be disappointed with the K20's high ISO performance to at least ISO 1000 or even a bit above.

If you want to reduce shadow noise at high ISO, set the exposure compensation to
+ 2/3 f-stops (this somewhat counterdicts the higher ISO setting), because this compensates for the Pentax tendency to expsose for the highlights.

External NR software always works better, than the internal camera engine (not a question of Pentax). For my needs LR does an acceptable job, but some specialised third party NR software does better (Noise Ninja & Co.).

Ben
02-26-2009, 08:00 AM   #14
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I'm coffee related deficiencies so forgive me if this is already been pointed out. Try and keep in mind when doing comparisons that just like with bokeh, there's actually some degree of noise quality not just noise quantity. I'm not sure I've seen a post processed noise reduction I like yet unless the noise was very subtle to being with. Some people hate any noise and they hated grainy film too. I personally hate the bubbly watercolor pixel effect of overdone noise reduction.
02-26-2009, 09:07 AM   #15
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QuoteOriginally posted by Mister Guy Quote
I personally hate the bubbly watercolor pixel effect of overdone noise reduction.
Same for me. I am almost never convinced by NR, I almost given up on NR software and I don't use it very much. Things start to loose texture with NR. The way some JPEGS are processed in P&S cameras is really awful in this regard. I may do some NR on textureless surfaces but that's about it.
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