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08-31-2015, 04:15 AM   #1
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Shutter speed for maximal effect of Shake Reduction

A few days ago I read the Service Manual for K10d. (You'll find a link here ) Chapter 33, for testing the different functions. Among them also the Shake Reduction.

It looks like the settings for testing the SR is very specific. That SR has a short range of shutter speeds where the effect is maximal. This is a copy/paste from Chapter 33-1:

*'*********
33-1. Confirmation of SR function
This confirmation is listed for [Method of confirmation for SR function on service]
[Preparation] Computer, Battery (or AC adaptor), USB cable, 50mm lens, SD card (for taking picture),
Image viewing software (e.g. PENTAX PHOTO Browser TM , ACDSee TM Adobe Photoshop, other)
① Attach the lens (FA50mm) to the camera and set the aperture to the A position.
② Set the camera as follows:
Exposure mode: Tv (Shutter-priority) mode,
Focus mode SW: AF.S mode,
AE metering: Center-Weighted Metering,
Single frame shooting (Fn Drive mode),
AWB (Fn menu), Recorded pixels and
Quality Level: [6M(10M)/★★★]
③ Set Tv8 (1/8sec) --- Approx.3.5 step

④ Set the camera 2m from subject.

⑤ Set the SR switch OFF. Hold the camera horizontal position (vertical position)
and take picture 10 frames.

⑥ Next, set the SR switch ON. Hold the camera horizontal position (vertical position)
and take picture 10 frames.
[Caution] To ensure the test, release the shutter after 1 second from SR indication
is turned on in the viewfinder.

⑦ View the pictures which have been taken above by the Image viewing software.

⑧ Compare the image of SR function ON with SR function OFF
and confirm the SR function effect to the picture.

[Caution] Effect of SR function may differ from condition of holding the camera.
[Reference] confirmation for SR mechanism (When use different type of focal length)
The shutter speed of prevention for shaking is calculate with [1 / focal length of the lens]

For instance, if the focal length is 200mm: 1/ (200 x 1.5) = 1/300
* Size of picture for digital camera is 23.5 x 15.7mm and it is about 1.5 times
when converting it into the focal length of 35milli-size camera.


① Calculate the shutter speed of prevention for shaking as above.
For instance, if the focal length is 200mm: 1/ (200 x 1.5) = 1/300

② Converts above shutter speed to three step down.
1/300 --> 1/150 --> 1/75 --> 1/30 (Approx. Three step)

③ Set Tv 30

④ Follow the procedure of 33-1, ④ to ⑧

[Caution] The effect of the shake reduction is influenced by the focal length of the lens and the object distance and effect might not become visible in the short distance (D-FA50mm Macro 0.4m), also an enough effect might not become visible at the low temperature.

*'*********
Doesn't this tell us that lenses shorter than 50 mm require too slow Shutter speed to be optimal? With a FA 50 mm, two meter from the subject, then I would definetely have chosen 1/60 - 1/125 (perhaps higher ISO) and no SR, rather then 1/8 and SR. I'm also a bit surprised to see that optimal Shutter speed for a focal length of 200 mm are not higher than 1/30.

"Optimal shutter speed"..., yes I know that this is the speed where the difference (to no SH) is easiest to observe. Does anybody know how much less the effect is when the Shutter speed is 2-3 steps higher?


Last edited by Dabola; 08-31-2015 at 04:23 AM.
08-31-2015, 05:03 AM   #2
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i think you are reading too much into this. the procedure here is to test that the system works and gives an example for testing the system this does not imply this is the limit of SR.

it applies to all lenses.
08-31-2015, 05:49 AM   #3
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QuoteOriginally posted by Dabola Quote
Doesn't this tell us that lenses shorter than 50 mm require too slow Shutter speed to be optimal? With a FA 50 mm, two meter from the subject, then I would definetely have chosen 1/60 - 1/125 (perhaps higher ISO) and no SR, rather then 1/8 and SR. I'm also a bit surprised to see that optimal Shutter speed for a focal length of 200 mm are not higher than 1/30.
It depends on what you shoot. Any shot where motion is in it, will put limits on how long shutter speed you can use. Otherwise there is no real limit on how long shutter speed you can use.
As long as you can use tripod with as long, or longer shutter speed to get the shot you want, the use of SR is not limited.

QuoteQuote:
"Optimal shutter speed"..., yes I know that this is the speed where the difference (to no SH) is easiest to observe. Does anybody know how much less the effect is when the Shutter speed is 2-3 steps higher?
It depends on how much camera shake there are. SR can only improve the shot if there would be visible camera shake in the shot without SR. But where that limit is depends on how steady you are at the moment you capture the shot. To get pixel perfect sharpness in every shot you might have to use 1/200s on a 50mm lens without stabilization.

What you normally accept as a sharp image can probably have a few pixels of camera shake.
08-31-2015, 08:41 AM   #4
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This applies equally to optical methods of stabilization. Short lens needs less speedy shutter to get acceptable results. Long lens needs more. Shake reduction is most effective toward the extreme end of its ability because the largest benefits come then.

08-31-2015, 09:24 AM   #5
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QuoteOriginally posted by Fogel70 Quote
As long as you can use tripod with as long, or longer shutter speed to get the shot you want, the use of SR is not limited.
You're not supposed to have SR turned on when you're using a tripod.
08-31-2015, 12:34 PM   #6
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QuoteOriginally posted by narual Quote
You're not supposed to have SR turned on when you're using a tripod.
What I meant is, in situations where you would benefit from a tripod, you can also benefit from SR (if you do not have a tripod available).
09-04-2015, 04:28 AM   #7
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I've been debating this for some time with myself. Assuming the reasonably accepted 1/focal length, converted to take into account the crop factor as a fast enough shutter speed not to need SR. Take 3 stops down as the practical limit of SR. For a 50mm lens, you have from 1/75s to 1/10s with SR giving benefit. Essentially in that range subject motion is very possible.

On the other extreme, for a 200mm lens, you have from 1/300 to 1/40 giving SR benefit. Again, subject motion is very likely.

I would like to know how much of a benefit there will be in the range faster than 1/180. In other words for a 500mm lens would the SR be able to react quick enough to offer any improvement. I realise that in-lens stabilisation is beneficial to enable one to see the view better, but in reality what improvement in IQ will there be when one needs a fast enough shutter speed to avoid subject movement? I gather that professional sports photographers generally switch IS off their lenses.
09-05-2015, 03:30 PM   #8
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Keep in mind that the number of stops benefit available tends to erode as you get much beyond the portrait lengths. For the longer lenses, you probably only get about two stops of benefit. So, I'm pretty comfortable shooting a 300mm lens at around 1/200th on the K-3. As far as sports photographers using long lenses and shooting around 1/800th or more - the SR on or off probably makes no difference either way.

09-05-2015, 03:55 PM   #9
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QuoteOriginally posted by ScooterMaxi Jim Quote
Keep in mind that the number of stops benefit available tends to erode as you get much beyond the portrait lengths. For the longer lenses, you probably only get about two stops of benefit. So, I'm pretty comfortable shooting a 300mm lens at around 1/200th on the K-3. As far as sports photographers using long lenses and shooting around 1/800th or more - the SR on or off probably makes no difference either way.
Though my technique might be off, I didn't even find a whole stop's benefit on the 50-200.
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