K7 Shake Reduction & Image Sharpness

Started Jan 26, 2010 | Discussions thread
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miles500
miles500 Senior Member • Posts: 1,216
K7 Shake Reduction & Image Sharpness

I should perhaps apologise for starting a separate thread from that relating to the AP review of SR systems. I am not so much concerned about the relative effectiveness of the Pentax system or the validity of the AP testing procedure, but rather with the question of whether a particular combination of settings can be the culprit in my search to find a reason why a high proportion of my images are not as sharp as I would wish.

Before anyone tells me to get a life and stop pixel peeping, I should say that I am looking to print out fairly fine detail up to A3 for competition prints and this I was able to do with my late lamented K200 and Sigma 17 -70 and as I am still processing images produced with that combination, I am aware of what can be achieved. I should also say that I realise that an image is never very sharp when viewed at 100% but I simply use that method to check the relative sharpness of images and the resolution of fine detail achieved.

I know that my K7 can produce very detailed and blur free images. I established this a few days ago when i took a large number of HDR images on a tripod of course and without SR. These were all as sharp anyone could wish. The following day I took a great many images of our new grandson using an external flash and again these were all very sharp and looked good even at 100%. Yet walking around the neighbourhood and taking a variety of handheld shots often in good light, the sharpness of many of them ( up to 50%) has been disappointing in terms of suitability for a large print.

Arising from the AP thread was the possibility that SR and Horizon Correction could be conflicting. As I had always had the latter enabled, I decided to switch it off and see whether that made a difference and a few test shots over my back garden showed a marked improvement in clarity.

To see whether I could replicate this with normal camera use. I photographed several local scenes using SR & HC; and SR only without SR. I struggled to find a pattern as for quite a few of the images there was no perceptible difference. It did , however strike me that a small number of very blurred images had one thing in common - SR+HC and a shutterspeed of 1/80 or more, whereas some of the lower speed images with the same shutter speed were very acceptable.

This morning I attempted to be more systematic. I took 10 images each of the same scene as follows: SR only/ No SR or HC; HC only; and SR +HC. (Focal length 17mm) Intentionally I set a high shutter speed 1/160 (the light must have faded for the last set which was only 1/125). I then compared them at 100% (four at a time). I could not differentiate between the majority of the images EXCEPT for the last set = SR+HC. Here about 3or 4 were rather less sharp than the rest, although the remainder of the set were OK. I conclude from this that HC is best avoided when using SR.

I also took 4 pictures of the same scene at 1/30 with SR; SR + HC; and with neither.

As one might expect those without the SR were not as good as those with SR. So Pentax SR does work - at least in my case! SR+ HC had no blurring effect and these were identical to those taken with SR only.

I have (I think) proved to myself that SR and HC are fine for low shutter speeds but for speeds above 1/50 ( am not sure where the crucial point is) HR should not be used when SR is enabled.

The recent (secret) firmware update 1.02.16 is said by some to have cured the problem of erratic sharpness at shutter speeds which should give sharp results, but it has not happened in my case.

I can not of course guarantee my findings as there are so many variables, but if others are experiencing the same difficulties as I have had, they might like to run a few tests of their own.

Ultimately one would hope that a firmware upgrade might address any conflict between SR and HC. I amd just trying to establish a workaround which will enable me to have the confidence that I can achieve the same consistently excellent IQ which I got with the K200. Maybe some copies (including mine) of the K7 are faulty.
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Miles500

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