Your point about a too thin adapter is well taken. But my point is that
you have no grounds to suspect the adapter is too thin just because
infinity focus is indicated at 3 meters. Even a moderately large print
taken at 3 meters focusing distance would show infinity well in focus.
If it can't be shown on an enlarged print one is certainly not able to
see it on the focusing screen no matter how good it is.
The best way to tell the accuracy of the adapter is to measure its
thickness with a micrometer or good quality caliper. For OM to EOS (46
vs 44mm) the adapter should be exactly 2mm thick.
Dr. Focus
Piers Hemy wrote:
> Quite so, Doctor, but it isn't just a question of DoF at the 3m setting.
> There's the usability factor too. With a too-thin adapter, there is a
> tendency to set the lens to focus beyond infinity, with the result that the
> effective DoF for earthly subject is much reduced. And with super wide
> angle lenses, it can be very difficult to spot that on the focusing screen.
> But I don't have any experience with a 5D, so it may not be as much of a
> problem as I had with an 8mm on an E-1 (even wider angle, even smaller
> screen).
>
> Buzz Lightyear
>
> -----Original Message-----
> From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
> Sent: 22 January 2009 13:36
> To: Olympus Camera Discussion
> Subject: Re: [OM] OM-5D, part II, Winter Pear Orchard
>
> The hyperfocal distance of an 18mm lens at f/3.5 (wide open) is only 2.8
> meters. Infinity is certainly already in focus at 3 meters... as is
> everything back to 1.5 meters. Not to worry about the adapter.
>
> Dr. Focus
>
>
>
> Piers Hemy wrote:
>> If the 8mm focuses at infinity when the lens shows 3m, I think you
>> need a thicker adaptor, not a thinner adapter.
>>
>> Piers
>>
>> -----Original Message-----
>> From: iwert bernakiewicz [mailto:zuikooh@xxxxxxxxx]
>> Sent: 22 January 2009 11:01
>> To: Olympus Camera Discussion
>> Subject: Re: [OM] OM-5D, part II, Winter Pear Orchard
>>
>> --snip
>>
>> The 18mm is very critical in focussing, I think the focussing ring on
>> my copy is a bit off maybe, being the 3m mark is already infinity. It
>> might as well be the adapter, I have ordered a second one which should
>> be thinner (adapter that is).
>>
>> --snip
>>
> --
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