Effectiveness of SR/OS/IS/VR Systems

Started Sep 29, 2010 | Discussions thread
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grahamdyke
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Effectiveness of SR/OS/IS/VR Systems
Sep 29, 2010

I have recently made some observations when carrying out non-scientific lens focus tests, on new lenses that I have purchased, with the below equipment:

Pentax K20D.
Sigma 17-70 f/2.8-4 HSM OS.
Sigma 50-150 f/2.8 HSM II.

With the K20D and Sigma 17-70 hand held and at shutter speeds that would not normally require any SR, or OS ie: 1/(focal length x 1.5). Comparing images at 100%
with:
1. Just the Sigma OS.
1. Just the K20D SR.
2. No SR, or OS.
The sharpest images always come from (3). The worst always come from (1),

when the shutter speed is greater than 1/(focal length x 1.5). The K20D plus SR (2) takes the middle ground.

With the K20D and Sigma 50-150 hand held and at shutter speeds that would not
normally require any SR ie: 1/(focal length x 1.5). Comparing images at 100%
with:
1. K20D + SR.
2. No SR.
The sharpest images always come from (2). The worst always come from (1),
when the shutter speed is greater than 1/(focal length x 1.5).

At shutter speeds less than 1/(focal length x 1.5), the Sigma OS wins out every
time over the K20D SR, or no OS/SR at all and the slower the shutter speed the
better the Sigma OS appears to get over the K20D SR.

My solution to this issue is to turn off all SR/OS where it is not required. Just
remember to switch it back on again for slow shutter speed work.

Perhaps this was how it was always designed to work? Would be interesting to
hear from owners of Sony's with Steadyshot and CaNikon owners with VR and
IS lenses and other Pentaxians with SR of course.

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Graham Dyke

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