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Re: [OM] M42 to OM 4/3 Adapters Revisited

Subject: Re: [OM] M42 to OM 4/3 Adapters Revisited
From: "Jim Nichols" <jhnichols@xxxxxxxxxxxxx>
Date: Sat, 3 Sep 2011 18:26:12 -0500
Chuck,

I think your original figures are correct.  I was just outside with my 
135/3.5 Takumar, and I checked its focus at infinity, and it seems to be 
correct with my adjusted adapter.

Jim Nichols
Tullahoma, TN USA
----- Original Message ----- 
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
To: "Olympus Camera Discussion" <olympus@xxxxxxxxxxxxxxxxx>
Sent: Saturday, September 03, 2011 5:09 PM
Subject: Re: [OM] M42 to OM 4/3 Adapters Revisited


> No wonder there's confusion.  According to one source I have the
> difference between 4/3 and M42 is 5.26mm.  According to another it's
> 6.79mm.  Both agree on the M42 spec but disagree on the 4/3 spec.
>
> Chuck Norcutt
>
>
> On 9/3/2011 12:33 PM, Chris Trask wrote:
>>>
>>>>
>>>>> It's now obvious that the problem has not been the thickness
>>>>> of the M42 mount plus adapter, but instead is an internal
>>>>> problem with the 400mm f/6.8 T4 lens.  Now I just need to
>>>>> find out how you adjust the infinity position of the focusing
>>>>> group inside the lens.  This is not a real problem as I also
>>>>> have the 400mm f/5.6 TX version, and it works just fine.
>>>>
>>>>
>>>> Someone else may want to correct me but I suspect you might
>>>> find a screw under the rubber of the focusing ring that controls
>>>> the position of the focusing ring and infinity stop relative to
>>>> the front lens group. Loosening the screw may allow turning one
>>>> relative to the other then retighten.
>>>>
>>>
>>>      The T4 lenses have machined aluminum control grips, but I will
>>> examine the focusing grip closely to see if there is a screw
>>> somewhere.
>>>
>>>      According to the parts list and breakdown drawing that I have
>>> for the later 400mm f/5.6 TX, there are three set screws at the
>>> bottom end of the focusing collar that are not concealed by the
>>> rubber grip.  And the focusing control stop appears to be a tab
>>> at the top end of that collar.  It's very likely that the T4 is
>>> similar in design.
>>>
>>
>>       Nope, but there's other screws everywhere.  I'll set that aside 
>> until I can find out for certain how to adjust it.
>>
>>       Looking at the TX/T4 to M42 to OM 4/3 combined adapters, I can now 
>> see that the proper thickness for the M42 to OM 4/3 adapter is somewhere 
>> between 6.0mm and 6.5mm, close to what you had calculated earlier.  Mine 
>> is 8.0mm, so I'll look around to see if I can find one of a more 
>> appropriate thickness that doesn't cause problems with the aperture pin.
>>
>> Chris
>>
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