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[OM] Re: (Double OT-Walt, do not read!) (Only for those with weak morals

Subject: [OM] Re: (Double OT-Walt, do not read!) (Only for those with weak morals.) EOS adapter with focus conformation chip
From: Moose <olymoose@xxxxxxxxx>
Date: Wed, 09 Aug 2006 14:29:20 -0700
Johnny Johnson wrote:
> ..........
> I ordered one of the Contax/EOS adapters and it arrived today.  It 
> came from Hong Kong, was well packaged and the fit and finish is very 
> good.  The camera sees the lens as being f2.0 so the high precision 
> sensors should be being used.  I gave it a focus test with a Contax 
> 50/1.4 lens and a target distance of ~three feet.  Starting at close 
> focus when the conformation light indicates focus the lens is 
> actually front focusing by about 1 1/2".  In contrast, starting at 
> far focus results in a front focusing error of 3/4".  In both cases 
> the target was out of the depth of field.
> .........
>
> I've read a few reports from people that were happy with their 
> adapter but more reports from folks that were experiencing problems 
> like mine.  So, if you decide to order one of these be aware that it 
> may not work as well as you hoped.
>   
Thanks for the info. A bit of a bummer, but life is still good.

Bye the bye, did you do this at full aperture? Or at least f2.8 or above 
actual lens aperture when focusing? Sounds like you did from your comments.

Perhaps setting it to tell the body it is f2.0 is causing some trouble 
with the high precision sensors? I did some testing with the Tamron 
90/2.8 AF in macro range on a copy stand and the focus confirmation was 
quite accurate, on a par with manual focus with good light, high 
contrast subject and no rush. So I wonder why it would not work in this 
situation.

Perhaps the camera is using the maximum aperture info to set something 
about its expectations about the image it is focusing on. It's obvious 
that telling it the lens is f2 and asking it to focus with the lens 
actually at f5.6 is unlikely to work, as the DOF of the image the sensor 
has to work with is too deep.

Maybe I'll get one later when they are down to $25. :-)

Moose

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