Total blur widths as a function of shutter speed for a Pentax K-7 camera (red) and a Pentax K-5 camera (green).
Our recent study of shutter-induced blur for the Pentax K-7 SLR camera has created a lot of buzz in the Pentax community. We are now actually watching to see similiar work been done for cameras of other vendors too.
Meanwhile of course I have been more than curious to see how the Pentax K-5 camera performs in this regard. I am glad to say that the lab work is done and a report is published. You may access it here (HTML and PDF):
In a nutshell: Pentax may not have changed much. But the little they changed helped. The increase of blur due to shutter operation (the amount which the image blur increases by at certain shutter speeds) is almost halved with respect to a K-7, at least at the most critical speed around 1/80s.
You may see this from the chart as depicted above as well. On average, the K-5 shutter induces a pixel blur increase by less than a pixel which should not be noticeable in day to day work. Normally, the increase is less due to other sources of softness or by not shooting at the shutter speed where the effect is largest.
Also note that every camera with a focal plane shutter (every SLR) will exhibit a certain amount of shutter blur for physical reasons.
We are not surprised to see the issue of shutter-induced blur for Pentax mitigated in the K-5. After all, the previous study for the K-7 was in reaction to numerous complaints and for the K-5, the first user feedback is very positive, incl. sharpness at the critical shutter speeds.
The conclusion cited from the white paper is this:
The shutter-induced blur in the Pentax K-5 is measurable but it should be small enough to be of no concern in day to day photography. The absolute magnitude of the effect sits halfway in between a K20D which has almost no measurable effect and a K-7 which exhibits an effect large enough to make some people notice in their work.
The matter may now have reached a satisfactory state with the K-5. But there remains work to be done for Pentax to fully understand and eliminate any unnecessary effects which compromise image sharpness.
It would be interesting to test another camera with fast shutter (like a D300s) to compare the absolute magnitude of the shutter blur effect which is never zero. Esp. at ~1/160 s. Ideally, vendors would measure it and make part of their cameras' shutter specification.