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12-09-2010, 09:41 AM   #1
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Does SR's effective diminish with focal length?

As focal length increases do you think SR's effectiveness diminishes, if so what focal length do you think it becomes virtually useless?

12-09-2010, 11:33 AM   #2
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QuoteOriginally posted by mikemike Quote
As focal length increases do you think SR's effectiveness diminishes, if so what focal length do you think it becomes virtually useless?
The camera uses the focal length input to optimize SR for the lens in use. Of course SR must be used with shutter speed suited to the focal length. The steadiness of the photographer is important also. This might be a nice subject for a series of test shots to determine your limits.

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12-09-2010, 11:50 AM   #3
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If you want proof of SR with a 500mm lens. Look at my last entry, about the equivalent of 3 1/2 stops I would judge.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/105926-shake-reduction-icon-exif.html
12-09-2010, 12:31 PM   #4
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Don't rely on SR, it is insurance, not an excuse to be sloppy. Shoot with the proper shutter speed (1/focal length * 1.5) if you can, and only go under as you find out where your limits are.

Everyone is different when it comes to being perfectly steady, so some people can go WAY under the standard rule, others, not so much. If you play within the rules, though, SR will ensure tack sharp photos every time.

Theres no replacement for shutter speed.

12-09-2010, 12:39 PM   #5
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QuoteOriginally posted by paperbag846 Quote
Don't rely on SR, it is insurance, not an excuse to be sloppy. Shoot with the proper shutter speed (1/focal length * 1.5) if you can, and only go under as you find out where your limits are.

Everyone is different when it comes to being perfectly steady, so some people can go WAY under the standard rule, others, not so much. If you play within the rules, though, SR will ensure tack sharp photos every time.

Theres no replacement for shutter speed.
More like, there is no replacement for a tripod.

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12-09-2010, 03:31 PM   #6
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I have posted the head of a heron shot at 1/40 using a 500 mm lens. I think SR works well a all focal lengths but regardless longer lenses still higher shutter.
12-09-2010, 03:50 PM   #7
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QuoteOriginally posted by mikemike Quote
As focal length increases do you think SR's effectiveness diminishes, if so what focal length do you think it becomes virtually useless?
Definitely the longer you go the more susceptible your camera is to motion and SR will help, but that is the key word help. It will not solve all blur problems and like you guessed, the effectiveness gets less and less the longer you go. I do not think that there is a point where SR becomes completely useless but I'm sure there is a point where is becomes very minimal, nevertheless it still helps.
12-09-2010, 03:54 PM   #8
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QuoteOriginally posted by fb_penpho Quote
If you want proof of SR with a 500mm lens. Look at my last entry, about the equivalent of 3 1/2 stops I would judge.

https://www.pentaxforums.com/forums/pentax-dslr-discussion/105926-shake-reduction-icon-exif.html
What do you mean 3 1/2 stops? Did you compare it to handheld without SR of the same subject and technique and obtained the same amount of blur at 3 1/2 stops faster shutter speed? Or are you comparing it to the guideline of 1/(FL * crop factor) ?

You need to do the former.


Last edited by Eruditass; 12-10-2010 at 09:27 AM.
12-09-2010, 07:41 PM   #9
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There can be some misrepresentations with respect to efficiency of SR. My example of 1/40 with a 500 mm lens is about 4 stops below the rule of thumb of 1/FL/ 1.5. for ASP-C sensors but technique also helps. I would bet I could probably Hand hold the lens at 1/400
12-10-2010, 01:49 AM   #10
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actually SR becomes less effective when the focal length gets shorter!

at very short FL's (wide angle) rotational motion becomes dominant over translation, and the SR can't compensate for rotational motion that well.

of course "less" effective in terms of stops of advantage over no SR. The 1/f (or 1/1.5f) rule still applies, so when f is small, the shutter speed can be lower.
12-10-2010, 02:06 AM   #11
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I read this somewhere, not sure if it's correct, so I guess it's better to be corrected here if necessary

The longer the focal length, the more susceptible to camera shake, and the the sensor needs to travel farther from the center to compensate.

The problem with in-body SR is the physical limit the sensor is allowed to move. I mean it can only go so far.

This physical limit is then more prominent the longer the focal length, hence diminishing effectiveness
12-10-2010, 03:36 AM   #12
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QuoteOriginally posted by paperbag846 Quote
Don't rely on SR, it is insurance, not an excuse to be sloppy.
No need to get sloppy, but no need to not rely on SR either. It does help.

QuoteOriginally posted by paperbag846 Quote
Theres no replacement for shutter speed.
There is in the case of the K-7 where the SR is so effective at 1/15 that the chances are higher to get a tack sharp image than they are around 1/100.


QuoteOriginally posted by orly_andico Quote
...at very short FL's (wide angle) rotational motion becomes dominant over translation,...
Actually, rotational shake is more problematic for longer focal lengths.

QuoteOriginally posted by orly_andico Quote
...and the SR can't compensate for rotational motion that well.
The SR mechanism can only compensate for rotational motion. Pentax cameras don't have sensors for translational shake.
12-10-2010, 05:53 AM   #13
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There is not a focal length at which SR is not useful (at least up to 500mm). Falconeye has done testing and found a little over one stop improvement with SR at 500mm, but more like 2 to 3 stops improvement at focal lengths under 100mm.
12-10-2010, 07:20 AM   #14
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I have been away from my comppuyter for a few days.


here is the image i noted shot at 1/40th using an SMC 300F4 and SMC-F 1.7x AF converter

This is 1/19 the rule of thumb shutter speed of 1/750 for a 500mm lens.

There is simply no way you could do this hand held without SR regardless of technique, which is obviously quite good regardless.


12-10-2010, 07:44 AM   #15
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Wow! That's exceptionally amazing... 300mm x 1.7 = 510mm @ 1/40th. That's about 3.5 stops, no?
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