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#1
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Tests of IS on Canon 75-300 IS
I've just been idly taking some comparison shots with a Canon 75-300 IS,
with and without stabiliser switched on. The results surprised me so much I repeated them several times to be sure. I used the lens at full telephoto on a 300D The "effective" length in 35mm FoV terms would be 480, so I would expect to need a shutter speed of 1/500. Speed 1/500 no IS : image slightly soft Speed 1/500 + IS : image pin sharp Speed 1/250 no IS : image soft Speed 1/250 + IS : image pin sharp Speed 1/160 no IS : image soft Speed 1/160 + IS : image pin sharp Speed 1/100 no IS : image soft Speed 1/100 + IS : image soft, visible double image, IS is worse **** Speed 1/60 no IS : image unusable, bad shake Speed 1/60 + IS : image shaky, smeared double image, IS is worse**** The conclusion I have to reach is that with "my" lens I get a marked improvement at the appropriate shutter speed and up to 2 stops down, but beyond that the image is actually WORSE with IS selected. (I must point out that these results are only relevant to this one sample - I haven't tried any other IS lens.) |
#2
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Tumbleweed wrote:
I've just been idly taking some comparison shots with a Canon 75-300 IS, with and without stabiliser switched on. The results surprised me so much I repeated them several times to be sure. IS shots can vary greatly from frame to frame at the limit of performance. IS is not an excuse to be sloppy. Best practice posture, holding technique and gentle shutter release will get the best results. The photo mags base their IS/VR/AS tests on hundreds of photo tests as they know that from frame to frame, the photog has variance in his movements. Cheers, Alan. -- -- r.p.e.35mm user resource: http://www.aliasimages.com/rpe35mmur.htm -- r.p.d.slr-systems: http://www.aliasimages.com/rpdslrsysur.htm -- [SI] gallery & rulz: http://www.pbase.com/shootin -- e-meil: there's no such thing as a FreeLunch. |
#3
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The conclusion I have to reach is that with "my" lens I get a marked improvement at the appropriate shutter speed and up to 2 stops down, but beyond that the image is actually WORSE with IS selected. IS adds its own form of shake. It's called noise. That's why you are supposed to turn IS off when using a tripod. IS is a negative feedback system. When there is "external" shake, IS might cancel much of it and that's great. However, with no external shake and IS switched on, there is always going to be some electrical noise in the sensors and in the servo amplifiers. This noise is sent to the moving lens element actuators, which causes a touch of blur. |
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