Image Quality

RAW and JPEG

Considering the aforementioned issues in capture with both underexposure, and consequently white balance and colour, I would deem it almost imperative to shoot either solely Raw or at least Raw+JPEG.

Noise is
more prevalent in Raw, owing to the lack of noise reduction, but detail is more finely preserved and chances are that noise reduction software will do a better job than in-camera.

Exposure

The Pentax K-m follows on in the grand tradition of Pentax cameras from days gone by in regularly underexposing.

As a guide, shooting with exposure compensation of +5 will provide more accurate results.
However, this tendency to underexpose can prove valuable if you’re prepared to do a bit of work in post-production, because it will maintain detail in potentially blown-out skies.

Noise

Noise control is impressive with the K-m, as was the case with the K200D before. There is virtually no loss in image quality up to ISO 400, with ISO 800 still eminently useable. ISO 1600 begins to see a loss in fine
detail owing to noise reduction, though differences between Raw and JPEG are negligible, while at ISO 3200 it’s very noticeable.

Tone And Contrast

The tonal range of the K-m may shed more light on the reason for underexposure, given the fact that highlights blow easily, owing to a narrow dynamic range, though detail is maintained well in the shadows.

Colour And White Balance

Colour rendition on the K-m is generally pleasing. The issues mentioned with underexposure do tend to have a knock-on effect with white balance – for example, when trying to set the correct amount of exposure
compensation, the white balance can shift with each setting, veering from warm to cold. However, if you shoot Raw and get the exposure right, any issues are easily amended in post-processing or the Raw conversion
process.

Sharpness And Detail

Considering that Pentax has stuck with the 10MP sensor rather than increasing the resolution, fine detail remains impressively rendered. The K-m adequately met the task of large-scale landscape work undertaken,though image sharpness was slightly lacking. Again, this is no great problem as a simple sharpening process in post-processing was more than adequate for the task.