I hear you but I think those problems are solved by looking for highly
rated sellers on ebay as well as asking here about other's sales experience.
Chuck Norcutt
On 12/5/2010 12:16 PM, Jeff Keller wrote:
> Badly built may not mean poorly machined. It may just be a case of taking
> their "standard design" and putting different locking tabs etc on it. The
> thickness could be way off as in the pictures I linked. Both were sold as
> Nikon to EOS adapters, and sort of worked, but the generic Chinese adapter
> was way off on its thickness.
>
> A soft corner could be caused by the adapter bayonet being the wrong depth.
> When the lens is mounted on the camera the lens could tilt down until the
> bayonet tabs finally caught the mounting flange. Many DSLRs have a prism
> housing that hangs out over the lens. It may not be obvious the lens isn't
> being held in the correct position.
>
> Keep in mind that there are millions of tiny anonymous manufacturers in
> China. Antifreeze in foodstuffs, toxic medicines: a lack of knowledge, a
> desire for a quick profit, no due diligence, anonymously produced can cause
> dramatic failures.
>
> Jeff Keller
>
> -----Original Message-----
> From: Chuck Norcutt [mailto:chucknorcutt@xxxxxxxxxxxxxxxx]
> Sent: Sunday, December 05, 2010 6:08 AM
> To: Olympus Camera Discussion
> Subject: Re: [OM] Changing lens mount
>
> I'm still having difficulty accepting this except in the case of
> extraordinarily badly built adapters. To put a corner out of focus the
> two faces of the adapter would have to be out of parallel by a
> ridiculously large amount by even the loosest standards of machining.
>
> To illustrate the point consider the notion of "depth of focus" as
> opposed to "depth of field". Depth of field equates to near and far
> focus points in front of the lens. The term depth of focus used to be
> used synonymous with depth of field but as it is now used equates to the
> position of the image plane of those near and far points on the image
> side of the lens.
>
> Now consider your wide angle lens. As an example I'll give you a 24/2.8
> focused at 15 meters (my guess at the distance to the porch as used in
> the test shots at 16:9). Using typical 35mm parameters for depth of
> field at f/8 the near focus point is at 1.9 meters and the far focus
> point is at infinity. On the image side of the lens the depth of focus
> is 0.54mm or 0.022". To cause notable differences in focus in one
> corner of the lens the two faces of the adapter would have to be out of
> parallel by so much as to probably be visible to the eye let alone a
> micrometer. Even wide open and focused only at one meter the depth of
> focus is still 0.003".
>
> I have three cheap ebay OM to EOS adapters. They work just fine except
> that two of them won't mount a couple of my non-Zuiko OM mount lenses
> although all Zuikos mount just fine. I've seen no problems with
> infinity focus and, although I haven't put a micrometer to them there is
> certainly no visually obvious difference in parallelism of the two
> mounting faces.
>
> Are you sure the FM forum correspondents aren't shills for CameraQuest?
> :-)
>
> Chuck Norcutt
>
>
>
>
> On 12/4/2010 11:51 PM, usher99@xxxxxxx wrote:
>> Perhaps stating the obvious but WA's are particularly
>> susceptible to adapter issues. Have seen several examples on FM alt
>> lens forum whereby
>> one side of an image was not sharp due to an uneven adapter. Never have
>> seen a complaint about a Cameraquest one, though may be overkill for
>> many applications.
>> Mike
>>
>>
>>
>> Looks like significantly more than 0.002" in the case of the 16-9.net
>> test:
>> http://www.16-9.net/lens_tests/15mm_2/sigma1224vnikon15f.html
>>
>> picture of adapters:
>> http://www.16-9.net/lens_tests/nikon_adaptors.jpg
>>
>> Jeff Keller
>>
>>
>>
>>
--
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