Dynamic range
The two dynamic range (D-Range) optimisation controls on the K-7 are Highlight Correction and Shadow Correction. When the Highlight Correction option is selected, the lowest available sensitivity setting is raised from ISO 100 to ISO 200. This allows the camera to underexpose to preserve the highlights.
Interestingly, when using this system, it is often possible to give images more than one stop of extra exposure and still not burn out the highlights. This allows the midtones and shadows to be brightened while keeping the highlights. Our lab tests measured the K-7’s default dynamic range at 12.2EV.
However, switching on the highlight correction sees it drop to 10.4EV because of its impact on the darker tones. Setting the shadow correction to the highest of its three settings brightens images and boosts the effective range to 12.5EV.
This graph shows the brightness values recorded by the test camera when it is used to photograph a stepped graduation wedge. The wedge has transmission values in 1⁄2EV steps ranging from 0 to 12EV. The camera’s exposure is set so the 12EV section in the wedge has a brightness value of 255. Software analysis of the image then determines the recorded brightness values of all the other steps and calculates the camera’s dynamic range.
Pentax K-7 Gamut
This graphic indicates that when set to the Adobe RGB colour space and its Bright Image Tone, the K-7 produces JPEG images that almost cover the sRGB gamut and most of the Adobe RGB space. As we often find, the greens of the Adobe RGB space are the biggest challenge, though purple, red and yellow are reproduced.
