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Manual focus only at minimum aperture?

 
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David



Joined: 03 Feb 2007
Posts: 3
Location: California

PostPosted: Sat Feb 03, 2007 7:27 pm    Post subject: Manual focus only at minimum aperture? Reply with quote

I have just become acquainted with these conversions and have joined this forum to try and understand more about the result. Is it true that one can only manually focus the 24-85 and 70-300 lenses at their minimum apertures? Obviously it is much easier to achieve precise focus with the lense opened up rather than stopped down. Excuse my lack of experience with the operations of digital cameras as I am still shooting film with my Contax N camera.
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MomoInu



Joined: 15 Aug 2006
Posts: 68
Location: Santa Fe, NM

PostPosted: Sat Feb 03, 2007 7:57 pm    Post subject: Reply with quote

Huh? I'm not sure what you mean. When converted to the Canon EF mount, these lenses will work just like any Canon lens on a Canon camera -- and just like they did on your Contax N1. It will be all auto-aperture and auto focus. All of which will occur at maximum (wide-open) aperture. The camera will stop the lens down to the correct aperture for exposure only when you press the shutter.
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David



Joined: 03 Feb 2007
Posts: 3
Location: California

PostPosted: Sat Feb 03, 2007 8:21 pm    Post subject: Reply with quote

My question originates from reading the General Questions section of this website. Under the topic Usage there is a reference to the necessity for the lens to be set at minimum aperture for manual focusing. I took this to mean that the lens must be stopped down completely in order to manually focus. Are you saying that the lens will remain at maximum aperture regardless of the setting on the aperture ring prior to actually snapping the shutter? I guess I'm also asking if the Canon digital cameras will allow full manual operation, setting both the shutter speed and f stop manually, and whether in this instance the lens will remain fully open, or will the iris close to the setting of the aperture ring? Thank you for taking the time to respond.
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conurus
Site Admin


Joined: 15 Aug 2006
Posts: 795
Location: Vancouver, Canada

PostPosted: Sat Feb 03, 2007 8:25 pm    Post subject: Reply with quote

Hi David,

The aperture of a converted lens is always controlled by the camera body. As a result, the aperture ring of the lens becomes useless. On the other hand, most Contax N-mount lenses do not have an AF/MF switch. Therefore, I am reusing that ring as AF/MF control. That aperture ring never decides the real aperture.

In the beginning, I thought of using the maximum aperture instead to designate manual focus. I did not do so because some lenses started at f/3.5, and it would have been only 1/2 stop to go from MF to AF for those lenses if I had gone that route. I wanted the UI of all lenses to feel the same, hence the decision.

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David



Joined: 03 Feb 2007
Posts: 3
Location: California

PostPosted: Sat Feb 03, 2007 9:45 pm    Post subject: Reply with quote

I see now. Thanks for the explanation. Now I suppose it's just a question of when to make the film to digital switch.
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mOnAmis



Joined: 14 Sep 2006
Posts: 29

PostPosted: Sun Feb 04, 2007 9:42 am    Post subject: Reply with quote

You might lament the loss of functionality of the aperture ring; its one of the things that make the Contax lenses what they are, BUT having the ability to switch from AF to MF without taking your eye away from the viewfinder is an unexpected bonus.

I'm sure conurus would have given us a working aperture ring if they could but its just not possible with Canon cameras.

My biggest gripe here and its nothing to do with the conversion, is that the front wheel on my 5D works in the opposite direction to what I expect. The aperture goes down when i expect it to go up!

Having got 4 lenses converted it is a real joy to be able to use them on a modern DSLR WITH the prospect of being able to upgrade the body when the time comes and keep the Zeiss glass.
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