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Topics - teedidy

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Lenses / Canon 24-70 f/2.8L mkii Focus Shift
« on: March 22, 2013, 12:22:35 PM »
HI All,

I have just received my (2nd copy) Canon 24-70 f/2.8 mk II. Being a faithful CR follower and reading http://www.canonrumors.com/tech-articles/how-to-test-a-lens/ I begain from the top and followed ever step I could as best as I could. I also have Reikan Focal and ran through every testing option there was available. What I have found suprised me to the point I originally thought I had received the dreaded bad copy.

There is a definite focus shift on the 24-70 mk II. I have found that from f4 to f5.6 it starts to back focus severely  -5 afma vs +3 afma for f2.8 to f4 and +3 afma f5.8 on.

I am surprised there is not more information already out there on this.
I Found this on a competing forum  http://www.fredmiranda.com/forum/topic/1177402 very similar findings

I understand through research you can hold the DOF button down to get around this issue? But would that reduce effectiveness of the f2.8 cross focus points?

After a quick search it appears the Tamron 24-70 has a very similar focus shift issue. 
http://www.lenstip.com/340.5-Lens_review-Tamron_SP_24-70_mm_f_2.8_Di_VC_USD_Chromatic_and_spherical_aberration.html

Does anyone have any advice? At this point I don't know what to do?

Thank you for your time.

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