Metering
The 77-segment multi-pattern metering system has already proved successful in the K-7, but in the 645D it really seems to excel. Images display a generally even range of tones that on occasion seem stronger on the darker tones, but always avoid losing any shadow detail. In most cases the evaluative metering tends to underexpose by between a half and a full stop, although at times this is preferable to help bring out the richness of the image and means that highlights are retained. From raw files it is possible to extract plenty of extra detail from even the darkest of shadow areas. The metering doesn’t seem to suffer from a tipping point in terms of exposure, as priority seems to be given to the brighter areas.
Image: The metering does underexpose slightly, but there is plenty of detail in the shadows that can be pulled out in processing
To test this I took a series of landscape shots with the bright sky taking up different proportions of the scene. Despite the variations in the histograms, the overall exposure and brightness only changed subtly through the range. Also on offer for more selective metering are partial and spot modes. The partial mode can work as a handy override for the evaluative mode, allowing you to obtain a brighter main subject at the expense of the surroundings.
An alternative is to use the generous 5EV exposure compensation to manually adjust your exposure. Although Pentax was unable to give the exact value, we believe the spot metering gives around a 2% coverage, which gives a very precise measurement from the centre point, although off-centre spot metering can be achieved using the exposure lock button and recomposing.
