September 23, 2014, 02:56:08 AM

Author Topic: Canon 5D3: How to find / calculate / figure out the Group in which a Lens is in?  (Read 2354 times)

John Thomas

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Hi,

In 5DMk3's manual (see pages 78-84), Canon divides the lenses in 9 groups based on how many Dual Cross-Type (if any), Cross-Type and Horizontal AF points a lens can exploit from the total of 61 AF points available.

The charts there are very nice, also the VIewfinder's blinking feature for the Horizontal AF points is ok, but how do I know in which group a lens belongs to, and I mean especially a lens which I do not own yet, a lens which I intend to purchase?

Of course, I mean lenses which aren't mentioned in the tables from the manual, either because are not from Canon either because are newer.

(For the nit-pickers: the aperture isn't sufficient to determine the group. For example there are f/2.8 lenses in groups A, B, C, D, E)

TIA

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3kramd5

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5D3, 5D2, 40D; Various lenses

JerryKnight

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Take a look at this, pages 37-39:

http://downloads.canon.com/CDLC/EOS_1DX_AF_Guide_CDLC.pdf

Good link, but if you get a "referral denied" message, just highlight your browser's address bar and hit enter to load it without the browser sending referral information... I didn't check to see if the browser refresh button works, but it might.

John Thomas

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Thanks a lot for the info and your intention (seriously) but, in fact, is the same info from the 5DMk3 manual. The problem is that, while there are some hints about aperture, macro and such, there isn't a clear rule to distinguish the groups between them. There doc is formulated with "Most large-aperture lenses...", "Some lenses..." etc., hence one can only guess a new lens in which group will be.

For example the EF 24-70 f/2.8 is in Group B while EF 24-70 f//2.8 II is in Group A. Why? And how can I figure it out?

A concrete question: The last Tamron 24-70 f/2.8 VC in which group is in? A certain Sigma f/2.8 lens? Tokina? (in few years) a new Canon lens?

This is my problem.

Ok, the best solution would be to have the AF engine render exactly the types in the ViewFinder (ie. including the Dual Cross-Type points) and someone publish them.

But thanks a lot anyway.


neuroanatomist

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For example the EF 24-70 f/2.8 is in Group B while EF 24-70 f//2.8 II is in Group A. Why? And how can I figure it out?

A concrete question: The last Tamron 24-70 f/2.8 VC in which group is in? A certain Sigma f/2.8 lens? Tokina? (in few years) a new Canon lens?

Group B lenses except for the 24-70mm are all f/2.8 primes of 28mm and wider - faster primes and all other zooms are in group A.  The 24-70 II follows the 'rule'.  Macro lenses break the rule because of the apparent aperture decrease with close focusing. 

No idea on the 3rd party lenses - they reverse engineer and 'spoof' the AF system (which has resulted in problems for Tokina and Sigma lenses in the past).  Those will have to be empirically determined. 
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Z

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I can't help but think the 24-70 f/2.8 was demoted to group B to encourage sales for the mark II. I doubt it, but the motive is there.

neuroanatomist

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I can't help but think the 24-70 f/2.8 was demoted to group B to encourage sales for the mark II. I doubt it, but the motive is there.

I might buy that if it was the only L lens in the group.  Rather, I think it might have something to do with the reverse zoom design, which the 24-70 II does not share.
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h4ldol

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Good link, but if you get a "referral denied" message, just highlight your browser's address bar and hit enter to load it without the browser sending referral information...

Thanks, it works now.

John Thomas

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For example the EF 24-70 f/2.8 is in Group B while EF 24-70 f//2.8 II is in Group A. Why? And how can I figure it out?

A concrete question: The last Tamron 24-70 f/2.8 VC in which group is in? A certain Sigma f/2.8 lens? Tokina? (in few years) a new Canon lens?

(snip) ....Those will have to be empirically determined.


Yes, this is the gist of the problem. And (AFAIK) we cannot. By pressing the AF chooser (the right-upper corner button) we can conclude for some groups only, based on the fact that for these groups the layout of the Horizontal AF points (which are blinking) is different.

But what can we do for the groups in which only the Double-Cross points are different?

...and now I'm thinking that, being an event / photo journalism / sports AF system, exactly these points can make the difference....

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