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07-23-2013, 11:39 PM   #1
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Selection of incorrect lens focal length - K-5

I was hoping to get confirmation from somebody with similar experience with a K-5 (which I have had the pleasure of owning for a couple of weeks).......I took several shots with a Sigma 15mm lens (manual focus) at shutter speeds of round 1/250s but ended up with quite severe blurring, presumably due to camera shake. I then checked my settings and discovered that the camera was still set for a 500mm mirror lens which I had used the previous day and in my haste to capture some early morning misty sunrise shots, forgot to change the setting accordingly.

Would this incorrect setting cause blurring even at such high shutter speeds ?

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07-23-2013, 11:42 PM   #2
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Perhaps the focussing is simply out?
07-24-2013, 12:15 AM   #3
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Mark, I doubt it as the aperture was set at f7.1. I have found the DOF of this lens to be incredible, so I can't believe that would be the cause.
07-24-2013, 12:30 AM   #4
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As I know, SR function needs and uses focal length for shake reduction, so, I think giving it such a wrong focal length, would make SR function do wrong!

07-24-2013, 01:12 AM   #5
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QuoteOriginally posted by jamesw Quote
I was hoping to get confirmation from somebody with similar experience with a K-5 (which I have had the pleasure of owning for a couple of weeks).......I took several shots with a Sigma 15mm lens (manual focus) at shutter speeds of round 1/250s but ended up with quite severe blurring, presumably due to camera shake. I then checked my settings and discovered that the camera was still set for a 500mm mirror lens which I had used the previous day and in my haste to capture some early morning misty sunrise shots, forgot to change the setting accordingly.

Would this incorrect setting cause blurring even at such high shutter speeds ?
I think you're lucky to only get that little amount of blur.

500mm is more than 30 times the focal length of what you were using!

As it is, I find it's quite easy to get blur at 1/250, when in a hurry.

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07-24-2013, 03:23 AM   #6
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QuoteOriginally posted by jamesw Quote
I was hoping to get confirmation from somebody with similar experience with a K-5 (which I have had the pleasure of owning for a couple of weeks).......I took several shots with a Sigma 15mm lens (manual focus) at shutter speeds of round 1/250s but ended up with quite severe blurring, presumably due to camera shake. I then checked my settings and discovered that the camera was still set for a 500mm mirror lens which I had used the previous day and in my haste to capture some early morning misty sunrise shots, forgot to change the setting accordingly.

Would this incorrect setting cause blurring even at such high shutter speeds ?
This is easy to answer if one thinks it through.

The SR system generates the same vibrations as the camera with a 500mm lens does, only inverted to cancel both vibrations out.

With a 15mm lens, you basically removed one of the two sources of vibration and you are left with one source. To speak precisely, you end up with the shake of the camera with a 485mm lens (500-15).

And of course, 1/250s isn't fast enough to stop the blur from a 500mm lens.

BTW, about the same happens if you accidentally have both, optical lens and sensor shift, stabilization switched on with a lens supporting it: 2 sources out of 3 cancel out, leaving you with 1 source, i.e. the effect as if no stabilization at all were active.
07-24-2013, 04:02 AM   #7
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QuoteOriginally posted by falconeye Quote
This is easy to answer if one thinks it through.

The SR system generates the same vibrations as the camera with a 500mm lens does, only inverted to cancel both vibrations out.

With a 15mm lens, you basically removed one of the two sources of vibration and you are left with one source. To speak precisely, you end up with the shake of the camera with a 485mm lens (500-15).

And of course, 1/250s isn't fast enough to stop the blur from a 500mm lens.

BTW, about the same happens if you accidentally have both, optical lens and sensor shift, stabilization switched on with a lens supporting it: 2 sources out of 3 cancel out, leaving you with 1 source, i.e. the effect as if no stabilization at all were active.
That makes sense. Thanks for the good explanation.
07-25-2013, 03:49 AM   #8
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Thanks for the tips and advice - at least I discovered what the problem actually was !

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