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04-30-2012, 09:44 PM - 2 Likes   #1
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K-7 vs K-x ISO Performance

Not sure if this is the right place for this, but there has been a lot of discussion here recently regarding the K-7 vs the K-x sensor, so I did a quick shoot to show the differences at ISO 200, 400, 800, 1600, 3200. Low light, just a stupid, dim floor lamp from Ikea directly behind the camera pointed at the ceiling, and my TV behind and to the left of the bobbling Sith lord.

Lens: Pentax-F 50mm f/1.7
Aperture: f/2.0
Spot Metering, exposure locked on the wood candle topper that Darth Vader is sitting on, then focused on his helmet
Shadow Correction: Off
Highlight Correction: Off
High-ISO NR: 1 Medium on both,
High-ISO NR Start on K-7: ISO800
Aperture Priority
Exposure Compensation at 0 for both cameras
Auto white-balance

I think those are the important bits, if anyone wants more info, check out the Exif or ask.
Shots are all handheld, so the lower ISO's probably have a bit of shake-blur. And it looks like I missed focusing on the helmet and got his chest a couple of times... but you should still be able to get an idea for the noise performance. The K-7 photos look a bit more underexposed than the K-x's, but I was just relying on the camera's meters.. I'm not sure what this will do to the noise between them.

They were shot in raw, so they were processed with lightroom, but it was just the default 'develop'.

ISO 100 (K-7)



ISO 200 (K-7)



ISO 200 (K-x)



ISO 400 (K-7)



ISO 400 (K-x)



ISO 800 (K-7)



ISO 800 (K-x)



ISO 1600 (K-7)



ISO 1600 (K-x)



ISO 3200 (K-7)



ISO 3200 (K-x)



ISO 6400 (K-x)



ISO 12800 (K-x)



I'm getting 100% crops together now.


Last edited by alstauffer; 04-30-2012 at 10:47 PM.
04-30-2012, 09:44 PM   #2
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100% Crops:

K-7 ISO 100



K-7 ISO 200



K-x ISO 200



K-7 ISO 400



K-x ISO 400



K-7 ISO 800



K-x ISO 800



K-7 ISO 1600



K-x ISO 1600



K-7 ISO 3200



K-x ISO 3200



K-x ISO 6400



K-x ISO 12800



It's a shame the focus isn't consistent across all of the shots, sorry: By the time I realized it, I had already moved everything.

Last edited by alstauffer; 04-30-2012 at 10:11 PM.
04-30-2012, 10:25 PM   #3
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There were a lot of threads on this topic in 2010. The general consensus was thar the K-7 IQ was superior at low ISO, while the K-x IQ was superior at high ISO (400 and above ).

A number a threads included some comparison with full Manuel settings to ensure that all comparisons were genuinely comparable. But ultimately the comparison is biased because the K-x was an entry level camera while the K-7 was a mid-range camera with more control.
04-30-2012, 10:44 PM   #4
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QuoteOriginally posted by hcc Quote
There were a lot of threads on this topic in 2010. The general consensus was thar the K-7 IQ was superior at low ISO, while the K-x IQ was superior at high ISO (400 and above ).
I had read about it in the past, but just did this for myself, to help me decide about moving to K-5 and/or selling my K-x, etc., and thought people here might want to see it. That sounds pretty much like what I am seeing here, though.

QuoteOriginally posted by hcc Quote
A number a threads included some comparison with full Manuel settings to ensure that all comparisons were genuinely comparable. But ultimately the comparison is biased because the K-x was an entry level camera while the K-7 was a mid-range camera with more control.
I should have done that, but the recent threads/discussions were talking/complaining about metering differences between the two cameras, too.

Why does that make it biased?

05-01-2012, 12:19 AM   #5
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QuoteOriginally posted by alstauffer Quote
Why does that make it biased?
alstauffer,
My comment about 'bias' is as follow: with the K-7, you have more controls than in the K-x and a comparison (eg at high ISO) with full manual settings might be less defavorable to the K-7 IMHO.
05-01-2012, 03:35 AM   #6
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A lot depends on exposure. The K7 really needs to be exposed to the right to look OK. There was a comparison with the K5, where the K7 did surprisingly well (https://www.pentaxforums.com/forums/pentax-k-5-forum/118608-k-5-vs-k-7-noise-...ml#post1225719). There is probably about a stop difference between the two cameras with regard to high iso. Definitely visible, but not the end of the world either.
05-01-2012, 05:40 AM   #7
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I agree with Rondec wrt ettr. I believe if you exposed right on both of these and then corrected in the raw converter, there would be less difference at high iso. Also, your K-X shots are brighter. This may be because you didn't set the same shutter speed on both. However, brighter photos will show less noise so this biases your test.
05-01-2012, 08:09 AM   #8
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QuoteOriginally posted by hcc Quote
alstauffer,
My comment about 'bias' is as follow: with the K-7, you have more controls than in the K-x and a comparison (eg at high ISO) with full manual settings might be less defavorable to the K-7 IMHO.
I don't really see where this bias comes into play; it seems you are implying that there's a bias toward the the K-7, but the K-x is said to have the better IQ. If the K-x 'wins' despite a bias toward the K-7, that's even worse for the K-7, no?

05-01-2012, 08:20 AM   #9
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QuoteOriginally posted by Rondec Quote
A lot depends on exposure. The K7 really needs to be exposed to the right to look OK. There was a comparison with the K5, where the K7 did surprisingly well (https://www.pentaxforums.com/forums/pentax-k-5-forum/118608-k-5-vs-k-7-noise-...ml#post1225719). There is probably about a stop difference between the two cameras with regard to high iso. Definitely visible, but not the end of the world either.
QuoteOriginally posted by L33tGreg Quote
I agree with Rondec wrt ettr. I believe if you exposed right on both of these and then corrected in the raw converter, there would be less difference at high iso. Also, your K-X shots are brighter. This may be because you didn't set the same shutter speed on both. However, brighter photos will show less noise so this biases your test.
Again, part of the discussion that prompted me to do this was about metering differences between the cameras as well. Exposure was calculated the same way for every shot; spot metering, exposure locked on the wooden candle jar lid - any exposure differences are based on the 'brains' of the cameras, I did not set the shutter speed to the same on both. For a scientific experiment, what I did wouldn't work; 2 variables (metering/iso performance) in one trial = no no, but this wasn't a scientific experiment for me, I do those all day. I was just trying to show differences in the cameras' performance. I tried to do the same thing with my E-PL1, but that 50mm lens on 4/3 sensor was way too long to take the same picture.

I didn't want to do any correction when converting to raw, because I thought that would count as 'cheating'.

*shrugs* If no one finds this useful, I can just take it down.
05-01-2012, 11:54 AM   #10
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QuoteOriginally posted by hcc Quote
There were a lot of threads on this topic in 2010. The general consensus was thar the K-7 IQ was superior at low ISO, while the K-x IQ was superior at high ISO (400 and above ).
That was not the general consensus. The K-x's sensor has significantly more DR than the K-7, even at low ISO. DxOMark - Compare cameras side by side
05-01-2012, 12:35 PM   #11
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I think honestly, we have known about this. When the kx came out, there were numerous threads: "I want a kx sensor in a K7 body." Well, that is basically what we have with the K5. Unfortunately, it costs a lot more than a used K7 costs. At the same time, the K7 sensor really does hit the same dynamic range/iso ability that was present with cameras like the D300, K20 and 50D that were being sold at the time that it was released. Since that time, there has been a significant improvement in high iso and dynamic range in APS-C cameras and in relation to those, the K7 doesn't look so good. Still, at low iso, it is decent, if not great.
05-01-2012, 01:03 PM   #12
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Hi Al. What raw convertor did you use? What settings for NR in the cameras?

I have a K20D and K-x. My testing with NR disabled was a 2/3 stop difference in noise (i.e. ISO 1600 on the K20D was cleaner than ISO 3200 on the K-x). From tests and net gab, my impression is that the K-7 is about 1/3 stop noisier than the K20D, therefore about 1 stop worse than the K-x. K-x and K-r are equal. Having done this test and with access to full resolution files, would you agree there's a one-stop difference in noise?

Aside from noise and 1.5 stops of DR, a K-7 is twice as much camera as a K-x.
05-01-2012, 01:05 PM   #13
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QuoteOriginally posted by alstauffer Quote
Again, part of the discussion that prompted me to do this was about metering differences between the cameras as well. Exposure was calculated the same way for every shot; spot metering, exposure locked on the wooden candle jar lid - any exposure differences are based on the 'brains' of the cameras, I did not set the shutter speed to the same on both. For a scientific experiment, what I did wouldn't work; 2 variables (metering/iso performance) in one trial = no no, but this wasn't a scientific experiment for me, I do those all day. I was just trying to show differences in the cameras' performance. I tried to do the same thing with my E-PL1, but that 50mm lens on 4/3 sensor was way too long to take the same picture.

I didn't want to do any correction when converting to raw, because I thought that would count as 'cheating'.

*shrugs* If no one finds this useful, I can just take it down.
No it's very useful. Even accounting for the exposure difference, it's a fair guide. Of course if the k7 underexposes like that, you would apply ev comp though.
05-01-2012, 01:09 PM   #14
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It's not that we don't appreciate the experiment and the effort taken perform it, but given the difference in focus and in exposure, it's hard to gauge much about difference in noise levels.

If you cared to repeat the tests, what I would recommend is using the same actual exposures for the shots on both cameras: eg, f/2, 1/30", ISO 1600 for both cameras, then f/2, 1/60", ISO 3200 for both cameras, etc. And since it can be so hard to get focus *exactly* the same between shots, I like to use a piece of fabric of or something similar, so I can compare the most in focus area of one against the most in focus area of the other.

Also be sure you have all in-camera noise reduction turned off, unless your purpose is to compare JPEG engines rather than sensors. But if that is your purpose, you also should make an effort to find the "best" NR setting for each camera, rather than assuming that the same setting on both cameras should mean the same thing. Generally, it's easiest to do these shooting RAW then processing the same program using the same settings. Or perhaps do a versipn where you try to find the "best" NR setting in your software for each camera, so you are comparing "best that can be achieved using a given PP program and just basic NR adjustments, no fancy extra plugins/filters/etc" for each. In some ways I personally find that more valueable than a comparison with no NR at all, and certainly much more useful than a comparison of JPEG,s who knows what level of in-camera NR.
05-01-2012, 03:41 PM   #15
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QuoteOriginally posted by Rondec Quote
I think honestly, we have known about this. When the kx came out, there were numerous threads
Looking at charts and numbers is one thing; actually taking pictures yourself and comparing them is another. I wasn't planning this as an end-all K-7 vs K-x thread and didn't even do this with the intent of posting it online, I had been reading complaints and debates that came up recently the day before, and did a quick test to relax after a final exam because it was too dark to shoot a real subject and my mind was too dead to start studying for my next exam. This was for personal use that I just thought I would post here for reference..

QuoteOriginally posted by audiobomber Quote
Hi Al. What raw convertor did you use? What settings for NR in the cameras?

I have a K20D and K-x. My testing with NR disabled was a 2/3 stop difference in noise (i.e. ISO 1600 on the K20D was cleaner than ISO 3200 on the K-x). From tests and net gab, my impression is that the K-7 is about 1/3 stop noisier than the K20D, therefore about 1 stop worse than the K-x. K-x and K-r are equal. Having done this test and with access to full resolution files, would you agree there's a one-stop difference in noise?

Aside from noise and 1.5 stops of DR, a K-7 is twice as much camera as a K-x.
Hi audiobomber. They were converted in LR3, without touching any of the settings. The NR in the cameras was set at 'Medium' on both, since that is how I've been shooting with them. 1 stop seems to be pretty accurate, but I am no expert I do agree with the last statement though; I've just gotten used to shooting with the K-x over the past 9 months, where I didn't really have to think about ISO until getting really up there.

QuoteOriginally posted by ihasa Quote
Of course if the k7 underexposes like that, you would apply ev comp though.
True. The ironic thing is, I've had +2/3 eV dialed on the K-7 for the past 2 weeks of shooting.. but reset it to do this test so that everything would be 'zeroed out'..

QuoteOriginally posted by Marc Sabatella Quote
It's not that we don't appreciate the experiment and the effort taken perform it, but given the difference in focus and in exposure, it's hard to gauge much about difference in noise levels.

If you cared to repeat the tests, what I would recommend is using the same actual exposures for the shots on both cameras: eg, f/2, 1/30", ISO 1600 for both cameras, then f/2, 1/60", ISO 3200 for both cameras, etc. And since it can be so hard to get focus *exactly* the same between shots, I like to use a piece of fabric of or something similar, so I can compare the most in focus area of one against the most in focus area of the other.

Also be sure you have all in-camera noise reduction turned off, unless your purpose is to compare JPEG engines rather than sensors. But if that is your purpose, you also should make an effort to find the "best" NR setting for each camera, rather than assuming that the same setting on both cameras should mean the same thing. Generally, it's easiest to do these shooting RAW then processing the same program using the same settings. Or perhaps do a versipn where you try to find the "best" NR setting in your software for each camera, so you are comparing "best that can be achieved using a given PP program and just basic NR adjustments, no fancy extra plugins/filters/etc" for each. In some ways I personally find that more valueable than a comparison with no NR at all, and certainly much more useful than a comparison of JPEG,s who knows what level of in-camera NR.
I wasn't planning on this being posted on the internet when I did it, I was just curious and passing time. Maybe after exams end I'll repeat it with everyone's advice taken into account and a subject easier to focus more consistently on (and a tripod.. I don't have steady hands so getting remotely usable ISO100-200 shots in that light was a bear). If I repeated it, I would also use the same shutter speeds on both.

As far as in-camera noise reduction, I had it set to medium on both, starting at ISO800. I had assumed (probably incorrectly) that they would be the same, since the bodies came out close to the same time, and I have been using them both on those settings since getting them. I didn't want to do anything at all in post-processing because IMO that's no longer comparing cameras. Finding the 'best' in-camera setting is a good idea though, and probably something I should have done anyway. I'll keep that in mind.

Does the in-camera high ISO noise reduction still process raw files, or only jpegs?

EDIT: Just searched, according to this link, the K20d does no NR on raw files, only jpgs. https://www.pentaxforums.com/forums/pentax-dslr-discussion/32501-high-iso-noi...thing-raw.html
I've read the same for the K-5, so I would assume the K-7 doesn't either. So ignore where I talked about NR settings, because I guess they're not doing anything.

Cliffnotes: There is no noise reduction in these images.
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