I don't think it was due to lack of machining skill. I think it was due to
not realizing the thickness matters ... use the same thickness for all
cameras, just change the locking pin etc.
I don't think a 0.001" error was the problem. The why (accepting that the
error was more than .001) is simply that as the lens focus ring is turned
the spacing between the elements changes. If the registration is off, the
spacing would never be correct between the film and all of the element
groups. If there aren't any floating elements then, the labeled range would
be off but the lens would work ... just as a bellows mounted lens has no
problems.
Jeff Keller
-----Original Message-----
From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
Subject: Re: [OM] Changing lens mount
I've read that same stuff and simply don't understand it. What is
inaccurate? Even a guy with a simple lathe in a machine shop can turn
an adapter that's accurate to within 0.001". If the thickness of the
adapter is off by +/- 0.001" how does that translate to terrible
results? Or is it not the thickness of the adapter but whether the two
faces are plano-parallel?
Chuck Norcutt
On 12/4/2010 5:12 PM, Jeff Keller wrote:
> If the lens has floating elements to compensate for close focusing, an
error
> in register distance can degrade the performance significantly. 16-9
tested
> a Nikon lens with a cheap adapter and got terrible results. When they got
an
> accurate adapter the performance was dramatically better.
>
> Jeff Keller
>
> -----Original Message-----
> From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
> Subject: Re: [OM] Changing lens mount
>
> To clarify, if the register distance of the adapted lens is shorter than
> that of the body being adapted to you can never reach infinity without
> inserting an optical element (which acts like a low power
> tele-converter). But you could use such a setup as a macro lens
> provided you don't mind not being able to focus further than a meter or
> two or three. However, even if the register distance of the lens is
> longer than that of the body it must be enough longer to accommodate the
> thickness of an adapter. One millimeter or thereabouts is probably
> about the practical minimum. The has to be enough metal for strength.
>
> Chuck Norcutt
>
> On 12/3/2010 3:43 PM, Andrew Fildes wrote:
>> No, but it means that you may not achieve infinity focus.
>> And as most lenses move a lot at the close end but not much at the long
> end, you may miss inf. by quite a lot.
>> Andrew Fildes
>> afildes@xxxxxxxxxxxxx
>>
>>
>>
>> On 04/12/2010, at 7:24 AM, AS wrote:
>>
>>> The differences in register are very small....sometimes a mm or less,
> what difference does that make? Does this affect the ability to focus?
>>
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