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Re: [OM] Was: mount mod; Now M42-to-4/3 Adapter Thickness

Subject: Re: [OM] Was: mount mod; Now M42-to-4/3 Adapter Thickness
From: "Jim Nichols" <jhnichols@xxxxxxxxxxxxx>
Date: Mon, 22 Aug 2011 15:24:14 -0500
Chris,

I think my statement caused some confusion.  It was poorly crafted, to say 
the least.

The lens that I referred to is a Leica-R Summicron 50/2, and must use a 
Leica-R to 4/3 adapter, so it won't work with the M42 adapter.  What I found 
with this lens is that the most distant object I can find comes into focus 
before the focusing index reaches the infinity mark.  I have to back off 
from the infinity stop to get it in focus.  This is the lens I used to see 
what an "infinity" image would resolve with my camera.

I compared the previous image, made with a Pentax Takumar 55/1.8 lens and my 
M42 adapter, to the Summicron image, and, at a distance, I find little 
difference.  As Chuck pointed out, it appears that the earlier image was 
made at a smaller aperture, because the foreground was sharper.

Jim Nichols
Tullahoma, TN USA
----- Original Message ----- 
From: "Chris Trask" <christrask@xxxxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Monday, August 22, 2011 2:58 PM
Subject: Re: [OM] Was: mount mod; Now M42-to-4/3 Adapter Thickness


> >
>> It had been a rough morning, Chuck, and I just didn't write it down.  My
>> point is, that I would seldom use a large aperture when shooting at
>> infinity, so the technical point about the thickness of the adapter is
> more
>> academic than useful.
>>
>> I appreciate your concern for the details, but I think I will let this 
>> one
>> slide by.  Thanks.
>>
>
>    Whoa, don't do that.  When I did my OOF test earlier I had the aperture
> set to f/22, so I suspect now that if I had opened it up to f/6.8 I would
> have seen OOF objects even closer.  I will keep that in mind when I redo
> that test after the thin M42/OM adapter arrives.
>
>    But now I have an additional question: You said earlier that the one
> lens you used would focus beyond infinity.  Do you still have that excess
> focusing available with the M42/OM adapter, or are you now just short of 
> it?
> If you had sufficient excess focusing travel on the lens, that would 
> explain
> why you are able to obtain infinity focusing with the thicker adapter.
>
>    The 400mm f/6.8 lens I've been testing has no focusing beyond the
> infinity mark, so any adverse thickness in the adapter would prevent me 
> from
> focusing at infinity.
>
> Chris
>
> -- 
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