I won't worry about the cheap adapter either, I did lots of lens testes on
over 30 OM Zuikos, never seen any problem from the adapter. If one has to
worry, worry about the lens itself. Check an example below for three lenses:
www.accura.com.hk/temp/Leica_M35_50_75.jpg
The field curvature is over 200 microns towards the edges.
C.H.Ling
----- Original Message -----
From: "Chuck Norcutt" <chucknorcutt@xxxxxxxxxxxxxxxx>
> For a 24mm lens at f/1.4 (if there is such an animal) the depth of focus
> for an object at 2 meters is 0.0933mm. Much smaller than the situation
> at f/11 but still 9 times larger than the 10 microns named as a critical
> value for lens adapter planarity in the article. I don't doubt Roger at
> LensRentals but I certainly don't understand what he's measuring. But
> since I've never seen the problem I guess I won't lose any sleep over it
> tonight. :-)
>
> Chuck Norcutt
>
>
> On 10/18/2013 6:01 PM, usher99@xxxxxxx wrote:
>> Dr. Focus writes:
>>>> As I was re-reading this it occurred to me to express the tolerances
>>>> here in another way. The depth of focus (the image side of depth of
>>>> field) is about 3/4mm or 75 times the stated required precision of 10
>>>> microns.
>>
>> Roger at Lensrentals did careful measurements on an optical bench at
>> F1.4 and I don't doubt the results.
>>
>> Recent comment on Ming Thein’s site that mentions: “Don’t think you can
>> get away with adaptors: the planarity of such adaptors is going to be
>> absolutely critical, especially with such short flange distances and
>> resolution numbers. You’ll actually be able to see the effects of a
>> cheap, out-of-plane adaptor – it looks a little like a tilt. (I know
>> this because I tried Hasselblad lenses on my D800E; none of the three
>> adaptors I obtained had sufficiently tight tolerances to avoid this
>> problem.)”
>>
>> He used expensive but 3rd party adapters--OEM might be better. The
>> adapters seem to induce a tilt and the physical large size of these for
>> these short registration distance cams
>> magnify the problem. Roger stated he is doing more experiments (in an
>> FM thread) with more adapters rotating every 30 deg or so to figure out
>> the issues.
>> That be said, as per Dr. Focus, stopped down a bit, shouldn't matter a
>> whole lot.
>> I hope some adapters will be more precisely engineered though.
>> Metabones already has a ver 111 adapter for Canyon EF to FF Sony with
>> probable AF and IS working.
>>
>> Adaptable Mike
--
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