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12-10-2014, 06:39 PM   #1
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Sensor noise on the K-5 II vs K-3

So, I understand that sensor size and sensor noise have an inverse relationship. I've also heard that on a given sensor size, a lower megapixel count with bigger pixels produces cleaner images. Now I can't comment on the pixel size part, but considering that the K-3 has 50% more pixels than a K-5 II, can I assume that the K-5 II would, theoretically, have better ISO performance? And if Pentax keeps improving their noise reduction algorithm (in software) in every hardware release, would that even things out? Does any one have real world experience with both cameras?

12-10-2014, 06:43 PM - 2 Likes   #2
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This part of the K-3 review compares it to the K-5ii in low light high ISO situations
Review: Pentax K-3 - Low-Light High-ISO | PentaxForums.com Reviews
12-10-2014, 07:02 PM - 1 Like   #3
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QuoteOriginally posted by groovyg Quote
So, I understand that sensor size and sensor noise have an inverse relationship. I've also heard that on a given sensor size, a lower megapixel count with bigger pixels produces cleaner images. Now I can't comment on the pixel size part, but considering that the K-3 has 50% more pixels than a K-5 II, can I assume that the K-5 II would, theoretically, have better ISO performance? And if Pentax keeps improving their noise reduction algorithm (in software) in every hardware release, would that even things out? Does any one have real world experience with both cameras?
At low ISOs, the K-3 flat-out delivers better image quality because of the increased resolution and better WB. At higher ISOs, while the WB is superior, the added noise counteracts the higher resolution. Thus, the final product from the K-3 at high ISOs is similar to what you'd get from a K-5 IIs.

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12-10-2014, 07:15 PM   #4
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QuoteOriginally posted by Adam Quote
At low ISOs, the K-3 flat-out delivers better image quality because of the increased resolution and better WB. At higher ISOs, while the WB is superior, the added noise counteracts the higher resolution. Thus, the final product from the K-3 at high ISOs is similar to what you'd get from a K-5 IIs.
Interesting, looks like there are more factors at play here than what I originally thought.

12-10-2014, 07:15 PM - 1 Like   #5
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My impression is that the K-3 is a bit noisier than the K-5IIs, but the noise of the K-3 is much easier to handle.
12-11-2014, 12:18 AM - 1 Like   #6
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QuoteOriginally posted by F-pix Quote
My impression is that the K-3 is a bit noisier than the K-5IIs, but the noise of the K-3 is much easier to handle.
Really? I haven't tried the K-3, but the full size shots I've looked at show a slightly more "blotchy" noise than the grainy and film-like noise of my K-5.
12-11-2014, 12:21 AM - 1 Like   #7
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QuoteOriginally posted by groovyg Quote
So, I understand that sensor size and sensor noise have an inverse relationship.
Correct, as long as you are using identical shooting parameters (e.g., the same f-stop).

If you use equivalent shooting parameters, the noise is exactly the same (bigger sensors do not have inherently less noise, they simply allow the use of brighter lenses).

QuoteOriginally posted by groovyg Quote
I've also heard that on a given sensor size, a lower megapixel count with bigger pixels produces cleaner images.
This is incorrect.

While it is tempting to believe that smaller pixels receive less light and hence are noisier, leading to a noisier image, the increased number of pixels offset the higher per-pixel noise. In other words, while per-pixel noise is higher with higher resolution sensors, their per-image noise is (pretty much) the same, everything else being equal.

Sensors often are based on different technologies and hence differ considerable in their noise performance. But in principle, the number of pixels on a sensor is not a factor for noise (within reasonable limits).
12-11-2014, 12:22 AM - 1 Like   #8
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While this isn't really what you are asking, in my view the improved AF performance of the K-3 easily makes up for any increased noise... and in practical use I haven't experienced any noticeable noise increase.

12-11-2014, 02:58 AM - 1 Like   #9
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QuoteOriginally posted by groovyg Quote
So, I understand that sensor size and sensor noise have an inverse relationship. I've also heard that on a given sensor size, a lower megapixel count with bigger pixels produces cleaner images. Now I can't comment on the pixel size part, but considering that the K-3 has 50% more pixels than a K-5 II, can I assume that the K-5 II would, theoretically, have better ISO performance? And if Pentax keeps improving their noise reduction algorithm (in software) in every hardware release, would that even things out? Does any one have real world experience with both cameras?
I have both cameras and like them fairly equally. Both perform to my liking, but I tend to use the K-3 more frequently.
12-11-2014, 06:41 AM - 1 Like   #10
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K-3 for terrestrial and the k-5 for astro, so far i prefer the k5 for long dark exposures but still experimenting with the k3
12-11-2014, 01:56 PM   #11
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Not news or rumor.
Moved to the proper forum.
12-14-2014, 08:26 PM   #12
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QuoteOriginally posted by Class A Quote
Correct, as long as you are using identical shooting parameters (e.g., the same f-stop).

If you use equivalent shooting parameters, the noise is exactly the same (bigger sensors do not have inherently less noise, they simply allow the use of brighter lenses).


This is incorrect.

While it is tempting to believe that smaller pixels receive less light and hence are noisier, leading to a noisier image, the increased number of pixels offset the higher per-pixel noise. In other words, while per-pixel noise is higher with higher resolution sensors, their per-image noise is (pretty much) the same, everything else being equal.

Sensors often are based on different technologies and hence differ considerable in their noise performance. But in principle, the number of pixels on a sensor is not a factor for noise (within reasonable limits).
Class A, thanks for the link to the DxOMark article - extremely informative!
12-15-2014, 04:27 AM - 1 Like   #13
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I shoot with a K5 II and a K3. It is virtually impossible to tell the difference between the images above iso 1600. Noise is equivalent and you can't really print bigger with the K3 (there isn't any extra detail that I can see). At low iso, the K3 does have more detail than the K5.

Noise feels easier to clean up with the K3 than with the K5, for what it's worth.
12-17-2014, 10:01 PM   #14
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QuoteOriginally posted by Rondec Quote
I shoot with a K5 II and a K3. It is virtually impossible to tell the difference between the images above iso 1600. Noise is equivalent and you can't really print bigger with the K3 (there isn't any extra detail that I can see). At low iso, the K3 does have more detail than the K5.

Noise feels easier to clean up with the K3 than with the K5, for what it's worth.
I've observed the same thing, and of course when ISO is less than 1600 noise isn't much of a factor either way regardless if the K3 has more of it or not.

I actually just processed an image at ISO 12800 from the K3 and was shocked at how clean it came out before I applied in NR. It was noisy, but I seem to recall 12800 being something I never touched with my K5. I'll have to see what happens at higher ISO's. I usually avoid anything over 6400.
12-18-2014, 05:57 AM   #15
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I thought that if you shoot similar scenes at the same settings with both cameras at the same resolution then the noise levels are about the same. You would need to downsample the 24MP K-3 shot to 16 MP to match the K-5. I don't own either camera but I thought I read this somewhere.
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