Pentax K-3 review – Noise, resolution and sensitivity
Image: Shown at 100% at 300ppi, the pull-up shows the fine detail that the K-3 can capture, although at ISO 400 a little luminance noise is visible if you look very closely
You would expect a 23.35-million-pixel sensor with no anti-aliasing filter to produce fantastically detailed images, and the K-3 doesn’t disappoint. The camera comes close to scoring a perfect 40 on our lens chart, which is something that, so far, only the Nikon D800/E and digital medium-format cameras have achieved. In fact, it is possible to make out all the individual lines at the end of the chart. However, there is moiré patterning and some slight, possibly consequent, artefacts, and that stops the K-3 producing a perfect result. As it stands, the K-3 falls just short, reaching 36 on the chart, rather than the perfect score of 40. That said, it is important to remember that this moiré patterning is visible from around 28 onwards, although this will, of course, only be an issue if you happen to photograph fine linear patterns – or indeed, test charts.
What really counts is the performance of the K-3 in the field. Here it is excellent at resolving all manner of fine details, which is particularly apparent when photographing landscape images. To make the most of the K-3’s sensor you must shoot raw files: JPEG images don’t resolve as much detail, only reaching around 32 on our test chart. Don’t get me wrong, this is still a very impressive figure, but it is only really what you would expect of a camera of this resolution – as we have seen, by not having an anti-aliasing filter, the camera is capable of far more. It would appear that the JPEG images have some anti-moiré effect applied, as there is only the merest hint of it when shooting JPEGs.
In terms of noise, the K-3 starts to show some signs of luminance noise in the shadow areas at around ISO 400, which shouldn’t be of any concern. At ISO 800, slight magenta/green colour noise can just be seen, although this is kept under control and it doesn’t actually get any worse until ISO 12,800 is reached. At the two sensitivities above this, slight banding is also visible in shadow areas.
Overall, sticking to the ISO 100-800 sensitivity range and shooting raw files produces highly detailed images with very little noise, particularly if images are well exposed. At the lowest sensitivities, the K-3 produces some of the most detailed images we have seen from a DSLR.
These images show 72ppi (100% on a computer screen) sections of images of a resolution chart, captured using the Sigma 105mm f/2.8 macro lens set to f/8 . We show the section of the resolution chart where the camera starts to fail to reproduce the lines separately. The higher the number visible in these images, the better the camera’s detail resolution is at the specified sensitivity setting.