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aeronation
Joined: 31 Aug 2012 Posts: 7
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Posted: Fri Aug 31, 2012 6:37 pm Post subject: Contax N 24-85/3.5-5.6 wider than Canon 24-70 |
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Did anyone find that your Contax N 24-85 with EOS AF conversion got a wider angle in the full range? The 24mm looks like 21mm, and 85mm even got a wider angle than 70mm @ Canon 24-70L. If need to, I can post comparison photos later
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hungmo

Joined: 11 Jan 2010 Posts: 35 Location: Hong Kong
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Posted: Sun Sep 02, 2012 2:07 pm Post subject: |
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Surprise me...
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amhlee
Joined: 27 Nov 2007 Posts: 35
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Posted: Tue Sep 04, 2012 2:33 pm Post subject: |
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Pls post photo ....
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aeronation
Joined: 31 Aug 2012 Posts: 7
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aeronation
Joined: 31 Aug 2012 Posts: 7
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amhlee
Joined: 27 Nov 2007 Posts: 35
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Posted: Thu Sep 06, 2012 5:03 am Post subject: |
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Did you set it on a tripod ?
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aeronation
Joined: 31 Aug 2012 Posts: 7
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Posted: Thu Sep 06, 2012 2:51 pm Post subject: |
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All those photos are put on a tripod while capturing.
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lam

Joined: 27 Apr 2008 Posts: 127 Location: Bangkok Thailand
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Posted: Fri Sep 07, 2012 1:18 am Post subject: |
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Good news , thanks for nice comparison.
I used to wonder why my N24-85 was so wide @ 24mm and fit my requirement for wide view that no need to purchase 21/2.8 distagon .
_________________ A man called Nalahm. |
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conurus Site Admin

Joined: 15 Aug 2006 Posts: 795 Location: Vancouver, Canada
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Posted: Fri Sep 07, 2012 7:47 pm Post subject: |
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very interesting. Did you experience the same phenomenon for objects at infinity?
_________________ I am a bird and I uncovered the E, EF and N-mount communication protocols! |
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aeronation
Joined: 31 Aug 2012 Posts: 7
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Posted: Tue Sep 11, 2012 3:53 pm Post subject: |
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I haven't tried on the infinity focus yet, I'll give it a try over this weekend. Secondly, I just bought the 70-200 from you and received it today, and do some comparison also. Finding the Contax 70-200 @ 200mm, the field of view exactly the same as my Contax 135/2 CY prime. And I compare with my Canon 70-200mm, it is also indicate closely to 135mm. I'll post the result within this week.
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aeronation
Joined: 31 Aug 2012 Posts: 7
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aeronation
Joined: 31 Aug 2012 Posts: 7
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conurus Site Admin

Joined: 15 Aug 2006 Posts: 795 Location: Vancouver, Canada
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Posted: Thu Sep 13, 2012 5:26 am Post subject: |
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I am no expert in optics... but the object distance is measured from the front principal plane and the image distance is measured from the rear principal plane. Those planes depend on the optical formula and could reside anywhere in the lens - or even outside of the lens! In any case, very unlikely to be the location where you set your tripod. (But admittedly your test shots are taken at a long-enough focusing distance for this effect to be negligible.) Zeiss always publishes this data in their literature but Canon never publicly discloses these parameters.
Also many lenses with internal focus designs have focal length changes as you focus closer, which I think is the primary reason for the anomaly you are experiencing.
Those were the reasons I suggested testing at infinity, since at infinity both effects were eliminated.
_________________ I am a bird and I uncovered the E, EF and N-mount communication protocols! |
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