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04-13-2010, 11:48 AM   #46
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QuoteOriginally posted by falconeye Quote
This is about the most confusing bullshit I have ever seen posted about image stabilization.


Why does somebody like jct us101 who posts so much posts about a topic he knows so little about?

Disclaimer: Because the post is so hopelessly wrong, I'll not going to react on whatever I receive as reaction.
Falk: I always enjoy reading your posts. This was the first that did not require me to pull out a math text book. I am glad that I am not the only one confused with this post.

Seriously, I have seen several posts lately that having SR turned on when it is not needed such as faster shutter speeds results in a degradation of image quality. Is there any truth to this? I am not talking about having SR on while using a tripod. I mean hand holding a 50 mm lens at say 1/500s with SR on.

04-13-2010, 01:19 PM   #47
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I have seen similar reports, although I think they were with the K7 prior to firmware updates. I personally have not seen anything along those lines. Basically, the camera knows the shutter speed that you are shooting at and takes that into account when it moves the sensor. On the other hand, if you have SR on and the camera is on a tripod, it doesn't know that fact and tries to compensate for movement that isn't there.
04-13-2010, 01:25 PM   #48
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Another nice thing about having shake reduction for primes is when using flash you can drag the shutter without the need of a tripod, allowing more ambient light into a shot. I was just playing around with that today and I really liked the flexibility it gave me.

As for why Canon decided to not put IS into more lenses, I imagine it was mostly a cost based decision. A 35 f/1.4L would be a monster with IS for example, but, I imagine, this would require a lens redesign, making it cost quite a bit more than the $1,400 it already does. I'm sure Canon looks at it like, "well we'll just make the high ISO results better and not have to build a whole new lens," and I don't fault their logic there.

I do feel people should give more credit to manufacturers like Sony and Pentax for having the shake reduction built into the body. I'm sure when Canon and Nikon get around to adding IS to their bodies nobody will claim it is useless. (Just like nobody will claim FF is unnecessary when Pentax ever gets around to making a FF camera)
04-13-2010, 02:20 PM   #49
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QuoteOriginally posted by Rondec Quote
I have seen similar reports, although I think they were with the K7 prior to firmware updates. I personally have not seen anything along those lines. Basically, the camera knows the shutter speed that you are shooting at and takes that into account when it moves the sensor. On the other hand, if you have SR on and the camera is on a tripod, it doesn't know that fact and tries to compensate for movement that isn't there.
Shake reduction kicks in only when there is a movement.

04-13-2010, 02:22 PM   #50
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Basically isn't there some kind of sensor gyrode in there that when the sensor moves so much in any direction due to shake while a photo is being taken, it processes that shake and corrects it? Does the Pentax SR work digitally on the photos or is it like the sensor takes another shifted image that then translates to the photo itself?
04-13-2010, 02:41 PM   #51
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QuoteOriginally posted by MSM Quote
having SR turned on when it is not needed such as faster shutter speeds results in a degradation of image quality. Is there any truth to this? I am not talking about having SR on while using a tripod. I mean hand holding a 50 mm lens at say 1/500s with SR on.
It happens that I've just finished a reinterpretation of the wonderful work of P.Smith.

First, go have a look at his admirable work:

-> Study of the Effectiveness of Shake Reduction in the Pentax K7

Well, I have plotted blur width (in pixels) with error margins against shutter speed (in ms) and do basically find a linear relationsship between blur width and shutter speed. Just as one may naively expect (cf. my attached graphics).

My results in a nutshell:
  • Result applies to a focal length of 50mm. Other focal lengths not studied!!
  • Result applies to the Pentax K-7 camera owned by P.Smith. Sample variation not studied.
  • Result applies to handholding shake of P.Smith. Other shakers not studied.
    -- end of disclaimers --
  • Shake reduction on/off has no significant effect at 1/100s and below.
  • Shake reduction is fully effective at 1/50s and above.
  • Shake reduction delivers an advantage of 3.0 stops between 1/50s and 1/8s (as derived by comparing the slopes of the two dotted lines in the graphics).
  • Shake reduction is most effective around 1/25s where it delivers an advantage in excess of 4.0 stops.
  • Shake reduction is less effective at 1/6s (and probably above).
  • With SR, acceptable blur widths (0-2px) are possible with 5x the exposure time (150 ms vs. 30 ms or 2.3 stops).
  • As a rule of thumb, shooting at x times 1/focal-s shutter speed yields 4x Ám shake without and 0.5x Ám with shake reduction (e.g., x=2 for 1/25s at 50mm).

In summary, SR delivers between 2.5 and 4 stops advantage in the range of shutter speeds requiring stabilization for 50 mm.


I heard that the efficiency of the Pentax SR at longer focal length is less while optical stabilization still delivers. This would be an interesting study to be carried out

However, there is no intrinsic barrier for supportable focal lengths with sensor shift image stabilization. The system's response time must be made small and acceleration be made high which makes it more expensive. Something more easily sold embedded in an expensive lens.

Last edited by falconeye; 06-15-2011 at 05:29 AM.
04-13-2010, 02:54 PM   #52
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QuoteOriginally posted by stanjo Quote
I just tested myself and can do 40mm 1/30 without SR no problem. I get ghosting at 1/10 and SR does help here.
However, if SR were not available, I could have taken the shot at 1/30 with higher ISO or just fix the exposure in PP (with K100D noise doesn't scare me).

In my reality, lack of SR for short/normal lenses is not a deal breaker. I'd trade SR for Canikon-like auto-focus.
Well, you are better than me then. I cannot reasonably get 1/30 hand-held pin sharp on every shot. So I rely on SR and it works! This is one of the major Pentax advantages. (I guess that's why some like to bad-mouth it or downplay its importance.)

QuoteOriginally posted by MSM Quote
Seriously, I have seen several posts lately that having SR turned on when it is not needed such as faster shutter speeds results in a degradation of image quality. Is there any truth to this?
With my K20D I have no problem whatsoever. I haven't micro-checked every image and I'm not going to waste time checking for some behaviour I never actually see.
04-13-2010, 03:30 PM   #53
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QuoteOriginally posted by jct us101 Quote
Does the Pentax SR work digitally on the photos or is it like the sensor takes another shifted image that then translates to the photo itself?
It is mechanical. Pentax have this PDF to download if you want the simple explanation.

04-13-2010, 05:10 PM   #54
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QuoteOriginally posted by manishved Quote
Shake reduction kicks in only when there is a movement.
Unfortunately, I don't think this is always true. If there is no movement and shake reduction is on, it can actually add movement. That is why Pentax recommends turning it off when shooting from a tripod.
04-13-2010, 09:43 PM   #55
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Critics of in-body SR should closely read P.Smith's and Falk's studies. Although each studied only a limited subset of possibilities, both STRONGLY support the value of in-body SR. If anyone has seen or performed valid studies showing otherwise, please present them. Criticism lacking data can be disregarded. (Mine included.)

EDIT:
QuoteOriginally posted by Rondec Quote
If there is no movement and shake reduction is on, it can actually add movement. That is why Pentax recommends turning it off when shooting from a tripod.
On the K20D, "Shake Reduction automatically turns off... when using self-timer, 2 sec. self-timer, remote control shooting, 3 sec. delay shooting, bulb shooting, or wireless mode with an external flash." (p.66) Also, "Shake Reduction does not compensate for blurring caused by movement of the subject... [SR] may not fully reduce camera shake when taking close-up shots... [SR] will not fully work when shooting with a slower shutter speed, for instance when shooting a moving subject or night scenes." (p.65)

So SR is automatically disabled in some situations, and is ineffective in other situations. How much criticism arises from not knowing these limitations and guidelines? If I don't get crystal-clear shots when shooting 1:1 macros of wind-blown flowers in low light, where does the blame lie -- the camera, or me?

Last edited by RioRico; 04-13-2010 at 09:54 PM.
04-14-2010, 07:38 AM   #56
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@Falk: Thanks for the link and you great insight. Much appreciated.
04-14-2010, 08:40 AM   #57
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Great stuff!

QuoteOriginally posted by falconeye Quote
It happens that I've just finished a reinterpretation of the wonderful work of P.Smith.

First, go have a look at his admirable work:

-> Study of the Effectiveness of Shake Reduction in the Pentax K7

Well, I have plotted blur width (in pixels) with error margins against shutter speed (in ms) and do basically find a linear relationsship between blur width and shutter speed. Just as one may naively expect (cf. my attached graphics).

My results in a nutshell:
  • Result applies to a focal length of 50mm. Other focal lengths not studied!!
  • Result applies to the Pentax K-7 camera owned by P.Smith. Sample variation not studied.
  • Result applies to handholding shake of P.Smith. Other shakers not studied.
    -- end of disclaimers --
  • Shake reduction on/off has no significant effect at 1/100s and below.
  • Shake reduction is fully effective at 1/50s and above.
  • Shake reduction delivers an advantage of 3.0 stops between 1/50s and 1/8s (as derived by comparing the slopes of the two dotted lines in the graphics).
  • Shake reduction is most effective around 1/25s where it delivers an advantage in excess of 4.0 stops.
  • Shake reduction is less effective at 1/6s (and probably above).
  • With SR, acceptable blur widths (0-2px) are possible with 5x the exposure time (150 ms vs. 30 ms or 2.3 stops).
  • As a rule of thumb, shooting at x times 1/focal-s shutter speed yields 4x Ám shake without and 0.5x Ám with shake reduction (e.g., x=2 for 1/25s at 50mm).

In summary, SR delivers between 2.5 and 4 stops advantage in the range of shutter speeds requiring stabilization for 50 mm.


I heard that the efficiency of the Pentax SR at longer focal length is less while optical stabilization still delivers. This would be an interesting study to be carried out

However, there is no intrinsic barrier for supportable focal lengths with sensor shift image stabilization. The system's response time must be made small and acceleration be made high which makes it more expensive. Something more easily sold embedded in an expensive lens.
04-14-2010, 10:00 AM   #58
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QuoteOriginally posted by RioRico Quote
If I don't get crystal-clear shots when shooting 1:1 macros of wind-blown flowers in low light, where does the blame lie -- the camera, or me?
The answer, my friend, is blowing in the wind.

(Sorry, couldn't resist!)
04-14-2010, 11:40 AM   #59
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Read all about it in this thread:

https://www.pentaxforums.com/forums/pentax-dslr-discussion/97590-pentax-shake...ited-test.html
04-14-2010, 11:53 AM   #60
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QuoteOriginally posted by jct us101 Quote
primes are not Canon's best area, considering how few they have, and how expensive that few is.
What planet are you living on??????????????????

Have you looked into the 24mm f/1.4L , 35mm f/1.4L, 50mm f/1.2L, 85mm f/1.2L, 135mm f/2L, 200mm f/2 L IS (and MANY MANY more I didn't list....) ?

As for expensive, the 85mm f/1.8 is an AMAZING lens for under $400 or so. That's quite a bit cheaper than the 77mm f/1.8 Limited (and has USM focusing )

What about the $90 50mm f/1.8? Not the best performing lens, but quite inexpensive (AND autofocus )
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