Based on the Pentax K-m, the latest K-x has inherited a number of features from the K-7 to entice the entry-level photographer. We put it to the test.
Resolution, noise and sensitivity
The 12.4-million-pixel sensor of the K-x doesn’t perform quite as well as other 12-million-pixel cameras we have tested. However, at ISO 100 it reaches 22 on our chart, which is better than the Pentax K-m.
Colour noise is well controlled in-camera at all ISO sensitivities. Looking at unedited raw files produced by the K-x, colour noise starts to appear at around ISO 400 but it only becomes a real problem at ISO 1600.
Even at ISO 12,800 both colour and luminance noise can be controlled in Adobe Camera Raw and it produces very good results given the ISO sensitivity. Pentax has obviously spent some time making sure that images are usable throughout the ISO range Although Pentax is clearly pushing the limits of what the 12.4-million-pixel sensor can do, the company has made it clear that the ISO 12,800 is an extended option, and not a default.
These images show 72ppi (100% on a computer screen) sections of images of a resolution chart, still-life scene and a grey card. 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.
The section of the still-life image contains the emblem on a standard-sized matchbox. The full scene can be viewed at http://tinyurl.com/67sj96. Images are taken using the Sigma 105mm f/2.8 EX DG Macro lens.