K20D vs. K7 in High-ISO RAW Noise

Greg Lovern wrote:

It looks like Santa may bring a used K20D or K7 this year. I'm still using my *ist D.

I recall much discussion, disagreement, and angst about whether the K7 was noisier than the K20D at high ISO, even in RAW. What's the truth?

Hi Greg,

I've also read that. However, in my opinion it is not enough of a difference to matter.

In my opinion the K-7 is a better camera in almost every way. See the differences side by side at:

• http://www.dpreview.com/reviews/pentaxk7/

Cheers.

Ron

The K7 handles like a much refined *istD and feels like a natural progression. The K20D size was enough to stop me upgrading from my *istD until the K7 arrived.

Greg Lovern wrote:

It looks like Santa may bring a used K20D or K7 this year. I'm still using my *ist D.

I recall much discussion, disagreement, and angst about whether the K7 was noisier than the K20D at high ISO, even in RAW. What's the truth?

Greg, yes there was a lot of "angst" over nothing IMHO. The K-7 has a little bit more noise due to the addition of circuitry to support video capabilities but it is hardly the end of the world with a difference of less than half a stop. This was confused somewhat when comparing images due to differences in compulsory raw data Noise Reduction (NR) with the NR for the K20D of the older more blotchy type (stronger) starting at ISO 1600 and the K-7 having the newer less blotchy type (weaker) compulsory NR starting at ISO 3200. The comparison in raw image quality between these two is minuscule when comparing either of them to the K-5 which really has about a stop less noise in the brighter parts of images and up to three stops less noise in the deep shadows.

If it were my choice between these two, I would likely pick the K20D if I weren't concerned at all with video and Live View and didn't mind the larger body (or liked it) and would pick the K-7 if I did want to play with those things and/or wanted a smaller camera body and/or wanted to use the newer user interface of the more modernized K-7; in other words, I wouldn't choose between them based on image quality at all.

Regards, GordonBGood

Greg Lovern wrote:

It looks like Santa may bring a used K20D or K7 this year. I'm still using my *ist D.

I recall much discussion, disagreement, and angst about whether the K7 was noisier than the K20D at high ISO, even in RAW. What's the truth?

I'm sure that measurements show the K-7 to be slightly noisier (see Gordon's post, for example) but I've found the two to be indistinguishable in real life. This is possibly because the K-7 meters a bit better, so exposure can be reliably a bit brighter - it is, of course, the dark areas that show noise.

There's the matter of sample variation and improvements through a product life cycle; but here's what the noise looks like on my K-7

compared to my K20

I think the best answer to your basic question is that noise isn't really the defining difference between the two cameras.

What I find much more significant is the ergonomics of the K-7, which seem more logical (although there isn't a vast amount of difference) and, especially, the rear LCD. 3" compared to 2.7" might not sound a lot but factor in the extra resolution (920k v 230k) and it's quite noticable in use. It makes focusing in LV a really useful tool rather than something that is just OK.

K-7 (taken with the K20)

K20 (taken with the K-7)

Both are at 8X magnification, which is where the K20 stops: the K-7 goes on to 10X. Here's the actual shot (taken with the K20)

I don't have an answer for your question, but considering buying used, the K20D bodies have no known issues, where the K-7 does.

Thank you
Russell

audiobomber wrote:

GordonBGood wrote:

This was confused somewhat when comparing images due to differences in compulsory raw data Noise Reduction (NR) with the NR for the K20D of the older more blotchy type (stronger) starting at ISO 1600 and the K-7 having the newer less blotchy type (weaker) compulsory NR starting at ISO 3200.

I've heard this statement before, but DXOMark shows both to have non-defeatable NR starting at ISO 3200 (signified by hollow dots on the SNR graph).

Dan, DxOMark are occasionally wrong in determining the exact point that NR starts using their autocorrelation tests. The Samsung GX 20 is essentially the same camera as the K20D in a slight different shaped body without Pentax's proprietary PEF format and DxOMark show it (correctly) to have Noise Reduction (NR) starting at ISO 1600. I have done my own autocorrelation tests on raw files from the K20D and confirmed that the compulsory raw NR starts at ISO 1600 for it as well.

Regards, GordonBGood

Russell Evans wrote:

the K20D bodies have no known issues, where the K-7 does.

Can you elaborate? I did a quick scan here and found two kinds of K-7 issues:
-- Issues fixed by firmware updates.

Greg Lovern wrote:

Russell Evans wrote:

the K20D bodies have no known issues, where the K-7 does.

Can you elaborate? I did a quick scan here and found two kinds of K-7 issues:
-- Issues fixed by firmware updates.

The shutter issue at 1/30-1/100s was never resolved. Whether it affected a tiny percentage, or not, is not really known. Whether it will be an issue for you I don't know. The only issue is not being able to return it if it is, or missing the return period because you didn't notice the issue in time.

http://forums.dpreview.com/forums/read.asp?forum=1036&message=35874725

http://forums.dpreview.com/forums/read.asp?forum=1036&message=34608194

http://forums.dpreview.com/forums/read.asp?forum=1036&message=35092203

Thank you
Russell

never seen this problem with my k7 15,000 pics

cheers don

hikenhi wrote:

Here's what you want to consider.
K-20D Pros--Slightly better IQ in Noise control

K-7 Pros:
-77-segment metering system to the K-20Ds 16-segment system
-3" 920,000 pixel LCD yo the K-20Ds 2.7" 230,000 pixel LCD
-740 average # of shots per battery to the K-20Ds 530.

-The K-7 is a smaller, lighter, more compact body constructed with amagnesium alloy shell.
-The K-7 shoots down to 14 degrees vs 32 for the K-20D

-The K-7 has more buttons with direct functionality including a direct ISO button which is available on the K-20D
-HD video, no video at all on the K-20D
-HDMI out

I don't have the K-7, just the K-5 so I'm assuming the two are mostly identical in the following.

The K20D's top LCD can be turned off and on without menu diving. It is seven clicks of button, wheel, and center dial, to turn it off and on on the k-5.

No mirror lock up with bracketing on the K-5.

The AF point selector is impossible to use with out taking you eye away from the viewfinder. I've press the Liveview button two out of five times in changing the selector switch.

The K-5 has more buttons only if you aren't in AF Select mode. This is really really annoying me has I can seem to find anyway to get into the flash, WB, or drive mode without first exiting the SELect AF point mode.

The setting of bracketing to the FX button is poorly implemented. The back LCD comes on even though you can set bracketing in the finder. When bracketing is enabled, a second push of the FX button doesn't disable bracketing and you can't turn if off in the finder like you can in the K20D.

My biggest issue though is with the k-5 grip. It really makes my fingers hurt after awhile. The K20D grip just fits my hand and I never had an issue with my hand hurting. I have realy small hands at that, so I don't think size has much to do with it. It is the shape of the grip. It is simply a lot more narrow so I end up carrying the camera with my finger tips.

It's not all roses and no thorns. I personally wouldn't say getting the K-7 is worse or better than the K20D, and would be happy with either. My point in posting is that it's not a slam dunk in favor of the K-7.

Thank you
Russell

I have both cameras, as mentioned IQ is indistinguishable. Personally I like the ergonomics of the k7 much more. Though it took a while to figure out the best button customizations, specifically the af point selections. I like the metal of the k7 better than the plastic of the k20, but I miss the locking accessory doors of the k20. I've had both cameras do long timelapses in direct rain with no leaks. My k7 spent 3 days on a tripod in constant rain with no cover and had no issues. With my k20 I fell off a boat and swam to shore with it my hand, no issues. I don't care about video, but I still think the K7 is a significant improvement, its more responsive, the AF is faster, the burst rate is faster, and I feel more comfortable with the button layout. Either camera would be a good purchase, I would buy from a place with a good return policy and keep the camera that feels better in your hands. Or maybe choose whatever's cheapest because the real investment is glass.