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12-14-2014, 04:30 PM   #1
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How precise does input focal length have to be so that SR will work?

I'm hoping this isn't a much too dumb question.
I don't know exactly for sure how SR works. Looking at the manual it almost sounds like it's only meant to compensate the movement induced by pressing the shutter. In that case maybe one should alway use the self timer instead where stability is crucial?
Not knowing exactly how it works, the question arises of how precise does the focal length have to be set so that it works ok. I can't have to be exact, since focal lengths rarely are just what comes printed on the lens. The question is more relevant for zooms, where some here consider that using a mid-range value is acceptable, so as to not have to change it each time one zooms in or out. Does anyone know for sure about this? Or how it would be possible to test meaningfully?
Thank you.


Last edited by Antonio Marques; 12-15-2014 at 02:54 AM. Reason: style
12-14-2014, 04:52 PM   #2
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I don't think it is too precise. Sometimes the WRONG input was found to give better results. The mid point on a zoom should be fine usually.
12-14-2014, 06:53 PM   #3
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QuoteOriginally posted by arnold Quote
I don't think it is too precise. Sometimes the WRONG input was found to give better results. The mid point on a zoom should be fine usually.
I've found it easier to just turn SR off when using an old zoom and just compensating by not shooting as slow, because inevitably I'll be using, say, my 75-260mm at 75mm, forget I have SR set to 75mm, then shooting at 260 for a while and screwing up my shots.
12-14-2014, 07:29 PM   #4
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Setting it too short is better than too long. The Q does an amazing job with shake reduction on long lenses I must say -- the tiny sensor must allow it to compensate faster/better.

12-15-2014, 06:05 AM   #5
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QuoteOriginally posted by Sagitta Quote
I've found it easier to just turn SR off when using an old zoom and just compensating by not shooting as slow, because inevitably I'll be using, say, my 75-260mm at 75mm, forget I have SR set to 75mm, then shooting at 260 for a while and screwing up my shots.
While I haven't looked in detail into how the SR works, I imagine that if you set the focal length too low, it would just under-correct. So, if you shoot at 260mm with the SR set to 75mm, the SR will still help reduce shake - but by only a third or so of the correct amount.

However, if you set it took long (e.g. set it at 260mm but shoot at 75mm), it will severely over-correct, adding shake in the opposite direction to the original. If I'm understanding it correctly, you're always safe if you tell the Q that the focal length of the zoom is the short end of its range.

That said, I think if I personally was shooting at an effective field of view equivalent of 260mm x 4.6 (for the Q7, x 5.5 for the Q/Q10) then I'd want the camera on a tripod anyway.
12-15-2014, 07:58 AM   #6
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About a year ago people here did some testing on SR settings and if I remember correctly some people (including myself) found a slight reduction in the setting provided better results. Like a setting of 105mm for a 135mm lens could provide better results. I believe that the Sr setting also is dependent on the steadiness of the operator. You must also remember that Pentax suggests you turn it off when using a tripod, my assumption here is SR could induce some blur in a steady camera. Heaving said all that, I think the SR input is not all that precise but for me important because I like to know the lens used. I also use a mid point leaning to the long side on Zoom lenses because I use the long end of most of my zoom lenses more often.
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