My camera uses sensor-shift (in-camera) image stabilization, which Pentax calls "Shake Reduction". This is activated on shutter half-press, and takes as long as a second to "settle" — if I take a picture faster than that, it's recorded in the metadata as "On but Disabled".

That's okay — I'd rather get the unstabilized shot than have to wait — but I'm wondering if this actually makes things worse than if I just left shake-reduction. Is it possible that the floating sensor is adding blur before it's locked in? I have the intuition that it might, and have heard as much in online discussions, but the manual only says that the system isn't effective before it's ready, not that it could cause problems.

On my normal prime lenses I'm usually either working carefully or at shutter speeds where SR isn't a big deal; with the DA★ 200mm indoors, I'm finding I'm often pushing against the shutter-speed-for-focal-length rule of thumb.

For my specific camera and immediate concern, I'm interested in Pentax's sensor-shift stabilization system, but I'd also like to know how other systems are affected, including both sensor-shift and lens-based.

2 Answers 2


Yes, an unsettled IS system will indeed cause blurring, ghosting, double-imaging, etc. I don't know if Pentax has in-camera IS or lens IS, and the characteristic blur from the Pentax may differ from what I get with my Canon IS lenses. I am also not sure exactly how long it might take a Pentax IS to "settle", however on my worst Canon IS lens, it takes less than a second. I know that sometimes a fraction of a second does matter, however as a general rule when using stabilized gear the rule of thumb is to shoot early and shoot often. You might notice sports photographers with the great white lenses usually shoot a couple seconds before any anticipated action actually occurs, partially to allow for IS settling.

I've learned a trick recently myself that helps with IS settling. I've started using back-button focus, wherein I've decoupled AF activate from my shutter button and configured a button near my right hand thumb as the button to activate AF. I normally use AI servo, but the same button works with single-shot AF as well. On a Canon, activating any one of AF, Metering, FEL, or shutter all initiate IS. By having independent control over AF, I also have independent control over IS, and I can usually keep IS activated if I anticipate the need to shoot, so by the time I actually do activate the shutter everything has already settled. I'm not sure if the Pentax supports reconfiguration of button functions, but if it does, you might try to separate AF control from shutter control, and give yourself a bit finer grained control over it all.

  • Yes; the higher-end Pentax cameras have a lot of buttons, including a dedicated one for AF. Partly based on suggestions here, I've set up the camera to de-couple half-press and autofocus, as yiou suggest. I'll have to check if the AF button activates IS, though, or if that stays with half-press even if AF is changed to not be.
    – mattdm
    Apr 5, 2012 at 13:32
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    Can you provide an example, reference, or documentation for the blurring, ghosting, etc.? The manual suggests that the shake reduction won't be effective until the system is stable, but does not warn against it possibly introducing problems.
    – mattdm
    Apr 5, 2012 at 13:36
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    Well, I could only provide examples of in-lens IS. Thinking about it, sensor-based IS would probably only really cause some amount of blur. The ghosting or double-imaging with in-lens IS is caused by the fact that the sensor will start exposing the moment the shutter button is fully pressed, then the IS will activate and shift and settle...so there is a partially-exposed "first exposure", and then the fully-exposed "primary exposure". Usually, neither exposure is sharp, as IS is not active yet for the first, and settling during the second, so you get blur & ghosting.
    – jrista
    Apr 5, 2012 at 15:13
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    I can't think of any way that ghosting or double-imaging could happen with sensor-based IS, since the projection from the lens never changes. However I can see how blur could be introduced by the sensor moving across the static image projected by the lens.
    – jrista
    Apr 5, 2012 at 15:17
  • @mattdm - Moving the AF off the shutter is generally a good idea, in my experience. I did that with my K20 and K-5 and not only does help in this aspect, but it's also good for recompose shots.
    – Joanne C
    Apr 6, 2012 at 4:05

It is my observation that it does. The technical reason is unknown to me but intuitively, I can see it happening when trying to match the frequency of your movements with the sensor's movement.

Luckily Pentax gives you a green light in the viewfinder when the system stabilizes. From memory, it does not do that in Live-View. When I did shoot before the stabilization icon appears I got pictures which were more blurry than usual but not always more blurry than without stabilization. For short focal-lengths (say 50mm or less), I would say it was worse than with longer ones.

A better system is Konica-Minolta's which is now on all Sony DSLRs and SLT cameras. This one gives you a Shake-O-Meter which tells you how much you are shaking (one a 5-bar scale). This effectively stabilizes the photographer who tries to keep the Shake-O-Meter low!

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