Shutter Blur on K7
Posted 20/09/2010 - 18:55
Link
It's (might be) sympathetic resonance, IIRC, it can happen with many systems where the resonance is triggered and amplified.
Bridges, musical instruments, sprung loads etc etc can all suffer.
I guess the sensor is mounted on some kind of dampened mount, sprung perhaps with something to move it to adjust for the shake. It might be the shutter movement at that speed is just right to set up a feed back in the SR, or sympathetic resonance in the mounting.
It might be worth trying holding the camera differently, attaching it to a tripod (even if you are holding the camera), using a grip etc etc. Turning off SR may counter-intuitively fix the issue.
The slightest change can affect system where sympathetic resonance occurs.
My car hums when the window is wide open, open the passenger window just a crack and the humming stops.
Bridges, musical instruments, sprung loads etc etc can all suffer.
I guess the sensor is mounted on some kind of dampened mount, sprung perhaps with something to move it to adjust for the shake. It might be the shutter movement at that speed is just right to set up a feed back in the SR, or sympathetic resonance in the mounting.
It might be worth trying holding the camera differently, attaching it to a tripod (even if you are holding the camera), using a grip etc etc. Turning off SR may counter-intuitively fix the issue.
The slightest change can affect system where sympathetic resonance occurs.
My car hums when the window is wide open, open the passenger window just a crack and the humming stops.
Lurking is shirking.!
Posted 20/09/2010 - 19:12
Link
Don wrote:
if that were the case you'd think the sr could be programed to offset it.
Don't think so, if you think that the force of the shutter is always the same than you're right.if that were the case you'd think the sr could be programed to offset it.
The problem is that the effect change depending on the weight of the camera (lens weight, flash, battery grip, ect.) and how a person holds the camera.
Therefore the movement of the camera is different every time.
Newton's second and third laws are in action here.
II. The relationship between an object's mass m, its acceleration a, and the applied force F is F = ma.
III. For every action there is an equal and opposite reaction.
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 20/09/2010 - 19:15
Link
johnriley wrote:
Not quite a focal plane shutter, but thanks for the link - it's ages since I saw that bit of film.
Funny enough the newest bridge in Rotterdam had the same problem but than with the cables.Not quite a focal plane shutter, but thanks for the link - it's ages since I saw that bit of film.
At certain wind speeds they started to vibrate, they have solved the problem though
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 20/09/2010 - 19:21
Link
Doug, I haven't read it though but the pictures does apply that that is the problem.
http://www.falklumo.com/lumolabs/articles/k7shutter/index.html
Very cool 1000fps movie from the K7 shutter http://www.falklumo.com/lumolabs/articles/k7shutter/K7-Shutter-Hispeed.mp4
This their conclusion.
http://www.falklumo.com/lumolabs/articles/k7shutter/index.html
Very cool 1000fps movie from the K7 shutter http://www.falklumo.com/lumolabs/articles/k7shutter/K7-Shutter-Hispeed.mp4
This their conclusion.
Quote:
When an SLR takes an image, it opens it's focal plane shutter. While it gets fully open, the shutter curtain accelerates and decelerates dramatically and then typically hits hard into the shutter box. As a result of this, the whole body accelerates significantly for a rather short moment in time (it gets a few„micro-kicks“). In the case of the Pentax K-7 camera, the shutter accelarations are a bit high and its floating sensor must then slip by a small amount (which isn't a bad thing as it counteracts the body movement due to shutter operation). But as a result of this, the camera electronics may struggle to get the floating sensor back into tight control. Or the imaging board may swing a little bit. Either effect magnifies blur to a level that it may become visible to the naked eye.
When an SLR takes an image, it opens it's focal plane shutter. While it gets fully open, the shutter curtain accelerates and decelerates dramatically and then typically hits hard into the shutter box. As a result of this, the whole body accelerates significantly for a rather short moment in time (it gets a few„micro-kicks“). In the case of the Pentax K-7 camera, the shutter accelarations are a bit high and its floating sensor must then slip by a small amount (which isn't a bad thing as it counteracts the body movement due to shutter operation). But as a result of this, the camera electronics may struggle to get the floating sensor back into tight control. Or the imaging board may swing a little bit. Either effect magnifies blur to a level that it may become visible to the naked eye.
Quote:
1. The K-7 has a heavier and/or faster shutter than the K20D, creating about 50 % larger body accelerations.
2. A sloppy, unstable, weak, ill behaving non-linear image sensor position controller magnifies the effect (for selected shutter speeds between about 1/180 s to 1/60 s) by another 100 %.
Or an equivalent non-linear effect is responsible for this, triggered by body acceleration (like a swinging imaging sensor board but not vibration alone!).
3. Combined, we see a 200 % extraneous blur effect increase compared to the K20D (3x its magnitude) leading to additional image blur in excess of 10 µm (on average). Which can be up to almost 4 pixels in worst cases (portrait orientation wide angle 1/80 s).
1. The K-7 has a heavier and/or faster shutter than the K20D, creating about 50 % larger body accelerations.
2. A sloppy, unstable, weak, ill behaving non-linear image sensor position controller magnifies the effect (for selected shutter speeds between about 1/180 s to 1/60 s) by another 100 %.
Or an equivalent non-linear effect is responsible for this, triggered by body acceleration (like a swinging imaging sensor board but not vibration alone!).
3. Combined, we see a 200 % extraneous blur effect increase compared to the K20D (3x its magnitude) leading to additional image blur in excess of 10 µm (on average). Which can be up to almost 4 pixels in worst cases (portrait orientation wide angle 1/80 s).
Stefan
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
K10D, K5
DA* 16-50, DA* 50-135, D-FA 100 Macro, DA 40 Ltd, DA 18-55
AF-540FGZ
Posted 20/09/2010 - 21:03
Link
Mike-P wrote:
I need to get a bigger brain ... or attention span.
No Mike, skip to the last line in the layman's summary, just like a real exec. dougf8 wrote:
oooooh, errrr,
Need to get a bigger tripod.
oooooh, errrr,oooooh, errrr,
Need to get a bigger tripod.
I need to get a bigger brain ... or attention span.
"It's not about vibration or a „loose“ image sensor and a massive tripod prevents it."
Cheaper than a new brain.
Lurking is shirking.!
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