K-x noise trial

I made these high-ISO tests for a friend who's considering upgrading to a newer Pentax DSLR, like the K-x. And then I thought they might be interesting to others. Even if you don't consider a Pentax, they will be similar to other contemporary DSLRs with a reduced sensor (which is pretty much all of them under $2000). Albeit the K-x, surprisingly considering size and price, is near the top end, according to reviewers.

I chose subject with shadow areas, since these tend to show noise more. And low depth-of-field for the same reason.

Note that I have turned off the noise reduction the camera does by default, since I've found that computer software does a better job (not surprising, given the demands of the tast). I have used Nik's Define, but others are good too.
If you leave the in-camera NR on, you'll probably get a quality which is in between what I show here before and after.

You have to click on them to see the differences.
Something which may not be clear in the resolution Blogger allows is that high-ISO downsides are not only about noise, but also less sharpness/detail. And noise-reduction, while it makes for smoother pictures, tends to make this worse.

ISO 1600, no noise-reduction:

ISO 1600, with noise-reduction:

ISO 1600, no noise-reduction:

ISO 1600, with noise-reduction:

ISO 1600, no noise-reduction:

ISO 1600, with noise-reduction:

ISO 3200, no noise-reduction:

ISO 3200, with noise-reduction:

ISO 3200, no noise-reduction:

ISO 3200, with noise-reduction:

ISO 3200, no noise-reduction:

ISO 3200, with noise-reduction:

ISO 6400, no noise-reduction:

ISO 6400, with noise-reduction:

ISO 6400, no noise-reduction:

ISO 6400, with noise-reduction:

ISO 6400, no noise-reduction:

ISO 6400, with noise-reduction:

I have put the link to the 28MB zip file of the full sized pictures in Comments.)

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If you want comparison to other cameras, I recommend DPreview.com and imaging-resource.com for that. Also just googling around.
And 1001 has just posted links to a couple of similar tests.