About OSS degrading image quality

Started Apr 29, 2013 | Questions thread
blue_skies
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Re: About OSS degrading image quality
In reply to jk2l, Apr 29, 2013

jk2l wrote:

As Zeiss said that OSS will degrade the IQ of the lens so they refuse to add OSS as part of the lens.

Can anyone explain why? is it the software part or mechanical part? What sort of degrading can we expect if they add OSS into it? is it the sharpness or the contrasts or what we are expecting here?

Also disabling the image stabilizing via in camera menu can this improve my IQ of my image that taken with the OSS lens? (e.g. SEL50F18)

Thanks

OSS CAN degrade a picture, badly even, but most often it makes little to no difference, especially if shooting at fast shutter speeds.

The inverse, camera shake, always degrades an image, and OSS can mitigate camera shake - up to several stops. Of course, it does nothing to reduce subject blur.

Three references on this that are worth reading:

  1. http://photographylife.com/lens-stabilization-vs-in-camera-stabilization
  2. http://www.bhphotovideo.com/indepth/photography/tips-solutions/image-stabilization-when-use-it-and-when-turn-it
  3. http://photography-on-the.net/forum/showthread.php?t=1103881

Zeiss is building non-OSS equipped lenses, but only up to 50mm. Sony initially intended only to include lenses at and above 50mm for OSS, as wider FL typically does not show a lot of sensitivity to camera shake. Their change to include OSS all the way down the 1018 is a pleasant surprise.

Because, in an OSS lens, a center (smallest point of lens) lens element is added that moves around, the lens has a 'deficiency' that relies on SW and HW algorithms to work together to mitigate lens movement. These algorithms are bound by FL and 'typical' hand movement. Either way, no matter how well implemented, an added lens element 'degrades' the lens optics. If not added, but a critical lens element, the entire lens is now more sensitive than without it.

As others pointed out - if you turn OSS off, you are not guaranteed that the lens is at its best, since the element is still in the light path, and may not be in the right position, nor be secured properly (floating).

Lastly, the trend is for lenses to include SW corrections for CA, aberrations, distortion. A company like Zeiss has long been making optically correct 'best' lenses, which work without such SW corrections. Lens designs are very tricky if they are optically 'best'. An OSS element most likely will defeat some of this 'best' qualities, resulting into a compromise of sorts.

Zeiss has said that they will NOT develop OSS lenses. I find it kind of odd, but this goes back to the discussion of IBIS versus OIS. On a Nex camera system, it means that Sony will only build "G" zoom lenses, and not "Zeiss" zoom lenses. Whereas on the Alpha SLT system Sony has lots of "Zeiss" zoom lenses (without OIS - the Alpha STL cameras have IBIS).

Regular handheld SEL18200 shot

Same SEL18200 handheld shot, moments before where OSS is moving the lens element (this is not a zoom-creatable effect)

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Cheers,
Henry

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