Low noise K-7

This is something that Greytop picked up on in the recent thread on the K-7's current price, & I thought it worthy of its own thread in the light of many people being unhappy with the K-7's high ISO performance compared to the K-x.

It seems pretty clear that the K-x's high ISO JPEGs are amongst the best from any APS-C camera, but if you look closely at the graphs in the DPR page that Greytop linked to ( http://www.dpreview.com/reviews/pentaxk7/page16.asp ) you'll find that the K-7's RAW noise performance is as good as or better than the D300 and the 50D. In fact, the K20D outperforms all these cameras in terms of RAW noise! The K-7's performance is very similar to the D300, and its level of chroma noise is lower (i.e. better) than the 50D.

I missed this when I first read the review, and must admit to being a bit surprised by it after hearing so many people describe the K-7 (& K20D) as noisy. JPEGs are admittedly noisier than the competition, but they also contain more detail.

Jonathan

Thanks Jonathan, you've highlighted some important details there.

So what you are saying is that as well as being outperformed by a current lower priced model of the same brand the K-7 is also beaten by the camera it effectivly replaced?

Thats a good point, but isnt the extra noise on the K7 caused by the fact there is more circuitry in and around the sensor to handle the increase in FPS and the video offered by the K7. I beleive that the Nikon D300s is also slightly worse than the D300 for similar reasons.

Mind you, I think both the K20 and K7 get an unfair press about high iso noise. The K20 is better than its competitors and the K7 is equal to its competitors yet they are both percieved as being poor at high iso's, whereas, for example, the Nikon D300 is percieved as being good at high isos:

I think a lot of my trouble is that I am still using a K10D if I'm honest.

From my experience, on a RAW level, in terms of noise, the K20D and K-7 are similar enough for any difference to be accademic.

They both have more noise than the K10D (at the same ISO), but only on a pixel level rather than when comparing images of the same size.

Personally, I find the amount of noise disappointing with all these cameras at ISO 400+, but that would go for other makes too, and it's only recently that better sensors have been developed.

Except for pixel peeping purposes the noise level of a properly exposed ISO 800 image from the K20D is good enough even for printing at A4 size.

The problem in practice comes when cropping a lot, then the noise is magnifified to a disappointing level, IMO.

This is exactly what I found when I did a few tests between my K20D and my new K-7 just after it arrived in July last year.
Just to satisfy my own curiosity I used my FA 50 f/1.4 on both cameras to take a series of RAW shots in different lighting conditions at ISO 1600 and above. The results were so close to the point that it made no difference.
I was happy with that because I always considered the K20D to be a pretty good performer at high ISO (quite a marked difference to my old Oly E-510).

I agree. In addition, I find it's easier to get great higher ISO images from the K-7 starting with RAW files, and exposing to the right. WIth many cameras, care with exposure can make an enormous difference to how bad the noise is at higher ISO.

I'm not surprised that the K-7 did not improve on the noise of the K20D - given it now has 4 channel output to handle video. However, one improvement I've noticed with the K-7 is that I don't get as much purple fringing. The K20D was a little bit prone to this (it's a sensor issue as well as a lens issue) to the extent that I was getting it even with a Tamron mirror lens - which is pretty much immune to purple fringing. That problem has gone with the K-7.