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Sigma lens mount and PK

 
 
Luigi de Guzman
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      02-12-2004
Is there any truth to the rumour that the Sigma SA mount is in fact a
Pentax PK mount? or at least that the two are somehow inter-operable?


I've been lurking on Pentax-discuss, and I found this thread, or
fragment of one:

http://www.mail-archive.com/pentax-d...msg163488.html

In any event, this is pretty big. If it'll take manual-focus pentax
lenses, I'd snap up a reasonably-priced SD-9....

-Luigi
 
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John Bean
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      02-12-2004
On Wed, 11 Feb 2004 23:21:06 -0500, Luigi de Guzman wrote:

> Is there any truth to the rumour that the Sigma SA mount is in fact a
> Pentax PK mount? or at least that the two are somehow inter-operable?
>
>
> I've been lurking on Pentax-discuss, and I found this thread, or
> fragment of one:
>
> http://www.mail-archive.com/pentax-d...msg163488.html
>
> In any event, this is pretty big. If it'll take manual-focus pentax
> lenses, I'd snap up a reasonably-priced SD-9....


Not as simple as that. The SA is similar to PK - but not the same - and the
register distance is different. There are no mechanical couplings on the
SA, and the stopdown lever on a PK lens prevents it from being mounted.

However, a purpose-made adaptor for M42 is available from
http://www.d-shell.net allowing screw mount Pentax lenses to be used in a
manual-everything sort of way. Works very well.

--
John Bean

I tried to wrestle my inner demons once...
but they used to many illegal holds (Amanda McAllister)
 
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Luigi de Guzman
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      02-12-2004
On Thu, 12 Feb 2004 09:06:30 +0000, John Bean <(E-Mail Removed)>
wrote:

>On Wed, 11 Feb 2004 23:21:06 -0500, Luigi de Guzman wrote:
>
>> Is there any truth to the rumour that the Sigma SA mount is in fact a
>> Pentax PK mount? or at least that the two are somehow inter-operable?
>>
>>
>> I've been lurking on Pentax-discuss, and I found this thread, or
>> fragment of one:
>>
>> http://www.mail-archive.com/pentax-d...msg163488.html
>>
>> In any event, this is pretty big. If it'll take manual-focus pentax
>> lenses, I'd snap up a reasonably-priced SD-9....

>
>Not as simple as that. The SA is similar to PK - but not the same - and the
>register distance is different. There are no mechanical couplings on the
>SA, and the stopdown lever on a PK lens prevents it from being mounted.
>
>However, a purpose-made adaptor for M42 is available from
>http://www.d-shell.net allowing screw mount Pentax lenses to be used in a
>manual-everything sort of way. Works very well.


Well drat. It's such a pity that such an interesting sensor should be
wasted in a body that supports a lens line with no lenses faster than
~f/2.

Looks like I'd better keep filling up the piggybank for a *istD, or to
jump ship to Canon.

-Luigi

www.livejournal.com/users/ouij

occasional photos (comments always welcome), rantings, ravings.

 
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Jupiter
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      02-15-2004
I can also recomment the d-shell M42 adapter. A bit expensive but
very well made and comes with an M42/L39 adapter sleeve.

The SA mount is very similar to the PK mount, but has been stated the
body can't accept the mechanical diaphragm actuator. A Pentax-K
T-mount adapter WILL fit but doesn't lock. The locking groove on the
PK mount is exactly in the same position as the sprung pin on the SA
body and I suspect drilling through the groove to make a hole will
enable it to lock. I've just taken the mount off the back of a faulty
PK lens and with the d-shell adapter as a template intend to convert
it to Sigma-SA. The 3 bayonet flanges start in the same position but
2 are slightly longer than the Sigma version. A matter of grinding
them down to the appropriate length. That will then go on the back of
my Sigma 600mm mirror lens which currently has a Contax mount. Exact
registration's not so much of a problem with them as they tend to
focus past infinity anyway (apparently to accommodate thermal
expansion and contraction).

I use my SD-9 on a PK microscope adapter with no problem at all. It's
hardly likely to spin itself off that but I wouldn't trust a lens on
it without a proper lock.

The procedure (per d-shell) with a manual lens mounted is to set the
camera to aperture priority, select an aperture of f5.6 on the camera,
set the aperture on the lens to whatever you want and the camera will
select the appropriate shutter speed. This technique works fine,
regardless of whether you're using a manual lens alone, tubes, macro
bellows, lens reversed or body on a microscope adapter. Mirror lockup
also helps in these circumstances.

I'm not getting into the silly Canon/Sigma argument. I'm perfectly
happy with the camera and with the d-shell adapter it's become a
specialist macro/micro tool.




On Wed, 11 Feb 2004 23:21:06 -0500, Luigi de Guzman
<(E-Mail Removed)> wrote:

>Is there any truth to the rumour that the Sigma SA mount is in fact a
>Pentax PK mount? or at least that the two are somehow inter-operable?
>
>
>I've been lurking on Pentax-discuss, and I found this thread, or
>fragment of one:
>
>http://www.mail-archive.com/pentax-d...msg163488.html
>
>In any event, this is pretty big. If it'll take manual-focus pentax
>lenses, I'd snap up a reasonably-priced SD-9....
>
>-Luigi


 
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