Does focus shift differ between copies of the same lens?

Started Dec 18, 2012 | Discussions thread
SteveL54
Senior MemberPosts: 2,638
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Internal lens compensation for AF
In reply to Ryan Mack, Dec 19, 2012

Ryan Mack wrote:

I finally took some time to train myself to compensate for focus shift on my 50 1.4g and I was surprised how significant the shift was. I was wondering if other copies of the lens might have less shift or if this was just a property of the lens design.

Thanks, Ryan

Some lenses have internal adjustments to account for it's specific individual lens aberration's influence on focus shift and hence the phase detection AF.

See this post about the Best Focus Adjustment for the Canon EF 50mm f/1.8

http://forums.dpreview.com/forums/post/16995273

From that service manual:

"Correction set at 70% of maximum spherical aberration." "Correction varies with individual lens."

From the Nikon 18-70mm f/3.5-4.5G: A section entitled, "Aberration compensation data writing adjustment", describes the procedure and equipment to compensate the AF for individual lens aberrations.

Steve

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