Pentax, Nikon
For a very long time I have followed on the internet the debate around Pentax vs Nikon stirred by the new Pentax flagship, the K10D and Nikon’s twins D80/D200.
Being the proud owner of a K10D I did follow the tests (before my purchase) but the sting of curiosity has remained until today when I tested my tool against a friend’s new acquisition: Nikon D80. We didn’t really spend time to match all the details, but conditions were like this: ISO 200, full autofocus, full auto white balance. Beyond that, each machine was on its own. The Nikon D80 came with a grip (to match the weight difference as the Pentax is heavier and better balanced in hand) and its kit lens, a 18-135mm Nikkor wide/zoom lens on f3.5-5.6 and a Sandisk 4GB SD card as storage while the Pentax had image stabilization turned on, a Lexar Pro 1Gb SD card 133x and had a Sigma 17-70mm f 2.8-4.5 lens on.
First thing I noticed was the importance of a clean lens. Before shooting we both cleaned our cameras and me (who, by the way, I had been disappointed with my camera lately) was amazed by the difference this process made on the sharpness of my images. My images is a way of saying because for the test we each shot with the other’s camera, so the Nikon was used by me.
Another thing that comes to mind is that, man … having a fast card does make a difference. The D80’s continuous mode came to a screeching halt after each burst in order to write on the slow card while the Pentax kept on flying. This could also be due to the fact that the Pentax’s jpeg frames were almost half the size than those made by the Nikon. Later, in Photoshop, I combed the images trying to find traces of any extra info the Nikon might be capturing over the Pentax but couldn’t find any.
Overall, the image quality on similar shots was on the par, with the Nikon having more intense colors while the Pentax’s IS system really kicked in and adding extra sharpness on handheld shots. I must note that for some strange reason the D80’s AF system failed a couple of times on what was my attempt at a macro. What happened was that I tried to shoot a flower from close range and I eventually found the minimum range for that on which the camera would focus properly. However the camera didn’t allow me to release and when I moved back a bit, thinking it might be the lens’ fault, the camera eventually released but despite the fact that I did try to focus and measure again, the ring didn’t move and I got a really out of focus flower. This happened only twice but it did make me wonder.
Also, there were a couple of erroneous colors on both cameras, with the Pentax bringing some slight tints of mangenta near edges in dark shadows while the Nikon had some trouble pinpointing some hues in the green-ish range.
All in all, the test did make me feel proud of my camera. A week ago I was thinking of switching to a D200 but today’s lens cleaning changed that. However I am pretty sure that the Nikon was heavily held back by the lens. If I were to give advice, I’d say: get a damn D40x body and use the 4-500$ difference on a damn good lens because yeah you can find one in this price range.
For me, the IS system, the RAW dedicated button and the quick access to ISO/WB/flash correction push the K10D ahead since in other aspects the cameras are operated much alike … top screen, two wheels and a shutter release. AF control and lock are on both also.
My next step will be towards a zoom lens to complement my macro and I’ve chosen the Tamron 70-300mm f4-5.6 for that 
Happy shooting!