Originally posted by audiobomber 1. I wonder if there's a human factor involved too, not just the camera? The blur seems to me to be a harmonic disturbance. Harmonics are generated under certain conditions. Change the conditions and the results change. The fact that a good tripod eliminates the problem points to the fact that grip is significant, and so is the 50% margin measured in the test.
2. I am an excellent shot with a rifle. I believe some of that technique also relates to photography. I tested my K-x at 1/60, 1/125 and 1/250s and none exhibited blur. That may be because my camera is different somehow, or maybe I hold the camera differently (softer, harder, looser, steadier?). Or maybe my testing wasn't thorough enough.
3. I suspect someone will use this work to criticize in-body shake reduction.... Fast shutter speed generates oscillation in the sensor, causing blur in the image.
Ad 1. We managed to specify a testing situation exactly reproducing the effect but eliminating any human factor.
Grip won't help except if you have a veteran iron hand. The shutter moves the body by only ~10µm. The human skin is too soft and too thick to do anything against, whatever be your grip.
Ad 2. We made no statement about the K-x. And yes, thorough testing was what was missing prior to our work.
Ad 3. Yes, but we express the opposite opinion wherever we can. In-body shake reduction is great actually because theoretically it could counteract any shutter blur effect. The K-7 probably can't because the required frequencies are 10x higher. But it could be done in theory so the in-body SR approach is superior.
Originally posted by Class A P.P.S.: Pentax needs to start selling "Class A" tripods. Surely people will buy more of these now. Looking at my username, perhaps I should start selling them?
A 120mm x 60mm x 50mm thick iron plate with a tripod screw and a tripod hole upgrades any tripod to a class A tripod (it should reduce blur width from max. 11µm to max. 3µm and make it neglegible). It will help in muscle building too when shooting free hand
Selling them is a good idea. Shipping cost may be a little high though
Originally posted by cfraz Falk, you referred to a "static offset" blur component. If I interpret your charts correctly, it looks to cause on the order of 1px blur. Any thoughts as to it's origin?
Also, did you make any measurements with the camera in portrait orientation? One would expect the extraneous blur component to be midway between the 0 degree and 180 degree results, no?
You need to read the paper on Image Sharpness. In a nutshell: The static blur offset expresses the fact that even a
perfect image has blurred edges and you want them blurred to avoid the stair case effect on tilted lines. Moreover, no image is perfect in practice and there will always be significant blur in an image unrelated to shake.
Yes, we assume portrait orientation to be slightly worse than landscape but didn't measure it.
Originally posted by Eruditass I don't see how this changes the observation that SR was ineffective above 1/100s? Unless your data was simply extrapolated from 1/100s.
It does change the observation. The data wasn't simply extrapolated but at higher shutter speeds, shake became too small to be measurable exactly enough to differentiate. Except for very long focal lengths. And this is exactly how this study was started: by doing a 300mm measurement, first by Rüdiger, then by myself. So, we found it isn't SR but something else and continued to hunt it down.
Next will be to update the SR guide. It is too pessimistic for shutter speeds < 1/200s and long focal lengths.
Originally posted by Gimbal At least the K10 (and probably every other Pentax as well) has the sensor plate pressed between a sort of ball bearings. With this method they make sure that the sensor does not move in any other direction then the up/down left/right plane. But it also means that there is mechanical friction involved.
a simple PD regulator (but that is, as I understand it, only speculation from Lumolabs?)
The PD controller is our speculation. We had to assume some implementation to make quantitative statements if it could be involved in all of this. A variant of a PD controller was deemed to be the most likely implementation.
Friction may or may not be involved. But note that this alone wouldn't explain the difference between K20D and K-7.