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05-24-2010, 04:25 PM   #1
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SR Question

I know about setting the focal length on older primes, but what do you set the SR to on older zoom lenses? I've got a screw mount 85-210, but not sure what would be best to set the SR to.

05-24-2010, 04:38 PM   #2
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Ideally, of course, you'd change the setting every time you zoomed, but I doubt anyone does that. So assuming you want to just pick one setting, choosing too low a foal length is safe - it might not be as effective as it could be, but it's better than nothing. Setting too high a focal length could be worse than nothing (at least, if it's more than about twice the actual focal length. So the standard advance is to pick a number near the bottom of the range.
05-24-2010, 07:53 PM   #3
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Isn't there only and "on", "off" for SR? I always leave my SR on even if I have a M lens on. Unless Marc read something that I did not I believe the question was about SR and you should always leave SR on.

If the question was about inputing focal lengths for older zooms then you should choose the low end of the zoom.
05-24-2010, 08:45 PM   #4
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QuoteOriginally posted by KxBlaze Quote
Isn't there only and "on", "off" for SR? I always leave my SR on even if I have a M lens on. Unless Marc read something that I did not I believe the question was about SR and you should always leave SR on.

If the question was about inputing focal lengths for older zooms then you should choose the low end of the zoom.
Actually, if focal length is indeed somehow tied to SR operation, such as shutter speed being the deciding factor on where SR should occur, wouldn't choosing the long end of the zoom be most effective?

Edit: WRONG! Please see post #6 below by member pschlute for explanation...


Last edited by rhodopsin; 05-25-2010 at 05:58 AM.
05-25-2010, 01:19 AM   #5
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Along these same lines, when I'm using my OOOOLD Soligor 80-200 I put in 200 on startup. In my logic, at the 200 end the hand shake is more severe in the photo than at the 80 end.

Might be an over compensation for anything closer than say 180mm...but I don't use the lens unless I need the reach, so it's never an issue.
05-25-2010, 02:56 AM - 1 Like   #6
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QuoteOriginally posted by rhodopsin Quote
Actually, if focal length is indeed somehow tied to SR operation, such as shutter speed being the deciding factor on where SR should occur, wouldn't choosing the long end of the zoom be most effective?
No. The shutter speed does not affect the SR function. The SR will try to compensate for any perceived shake by moving the sensor by an amount relative to the focal length used (either read from the lens or in the case here , from an input FL)

If the camera thinks/knows you have a long lens on the camera it is aware that a certain "shake" of the camera will lead to a more pronounced blur than with a shorter FL and thus will compensate by moving the sensor to a greater degree.

Thus if you input 200mm, and use the zoom at 80mm you will get an overcompensation from the SR. This is not good.

If you input 80mm and use the zoom at 200mm you will not get enough compensation, but this puts you in no worse a position than not using it at all.

Last edited by pschlute; 05-25-2010 at 06:06 AM.
05-25-2010, 03:01 AM   #7
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it may be most prudent to re-enter the focal length whenever you zoom in/out significantly ... maybe you make some ranges of focal lengths and update the value when you move from one range to the other ... I agree with the view that if you enter an extreme value and shift to the other end then you will over/under compensate ...
05-25-2010, 04:19 AM   #8
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Recommendations are definitely to input the wide end of the zoom as the focal length. It is far better to undercompensate than to over compensate. If you know that you will primarily shoot at the long end, that would be different perhaps.

05-25-2010, 05:55 AM   #9
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QuoteOriginally posted by pschlute Quote
No. The shutter speed does affect the SR function. The SR will try to compensate for any perceived shake by moving the sensor by an amount relative to the focal length used (either read from the lens or in the case here , from an input FL)

If the camera thinks/knows you have a long lens on the camera it is aware that a certain "shake" of the camera will lead to a more pronounced blur than with a shorter FL and thus will compensate by moving the sensor to a greater degree.

Thus if you input 200mm, and use the zoom at 80mm you will get an overcompensation from the SR. This is not good.

If you input 80mm and use the zoom at 200mm you will not get enough compensation, but this puts you in no worse a position than not using it at all.
Ah, thank you, that makes more sense. Focal length input adjusts accelerometer(s) sensitivity. My original post is edited.
05-25-2010, 08:29 AM   #10
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QuoteOriginally posted by pschlute Quote
No. The shutter speed does not affect the SR function. The SR will try to compensate for any perceived shake by moving the sensor by an amount relative to the focal length used (either read from the lens or in the case here , from an input FL)

If the camera thinks/knows you have a long lens on the camera it is aware that a certain "shake" of the camera will lead to a more pronounced blur than with a shorter FL and thus will compensate by moving the sensor to a greater degree.

Thus if you input 200mm, and use the zoom at 80mm you will get an overcompensation from the SR. This is not good.

If you input 80mm and use the zoom at 200mm you will not get enough compensation, but this puts you in no worse a position than not using it at all.
Thanks for the explanation. I never thought about SR in that manner. That will be very helpful with my MF zooms.
05-25-2010, 09:17 AM   #11
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From Pentax (company) on facebook:

"Since the older lenses do not send focal length information to the camera body, the user will need to enter a focal length for the lens into the Input Focal Length screen. If the lens is a zoom lens, enter a focal length value mid-way between the bottom and top of the zoom range for that lens. For example, for a 70-200mm zoom lens, enter a focal length of 135mm. This is an easy way to provide the benefit of shake reduction across the entire zoom range."
05-25-2010, 09:31 AM   #12
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QuoteOriginally posted by Marc Sabatella Quote
Ideally, of course, you'd change the setting every time you zoomed, but I doubt anyone does that. So assuming you want to just pick one setting, choosing too low a foal length is safe - it might not be as effective as it could be, but it's better than nothing. Setting too high a focal length could be worse than nothing (at least, if it's more than about twice the actual focal length. So the standard advance is to pick a number near the bottom of the range.
Marc, thanks, I always wonder what should I set the SR in a manual zoom. This answered my question.
05-25-2010, 12:00 PM   #13
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Thanks for all the reply's. When I was out, I wasn't sure what to set it to, so I ended up just turning the SR off. Next time I'll try it on the low end and see what happens.
05-25-2010, 12:14 PM   #14
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QuoteOriginally posted by eccs19 Quote
Thanks for all the reply's. When I was out, I wasn't sure what to set it to, so I ended up just turning the SR off. Next time I'll try it on the low end and see what happens.
I think the most convenient setting is along the lines suggested by enoeske. Somewhere in the middle, although I would personally err on the shorter side, but not the shortest setting, so for an 80-200 I would go with 110.

Of course if you are going to be mainly shooting at 150-200 range then you should use around 170.
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