Pentax A SMC 1:2 50mm Quick Release Camera Lens SLR

[graham_powell1]

Hi!

 

I've just bough one of the above on Ebay, but I'm not sure exactly

what it is I have. The 'quick' release certainly seems to have little

to do with fixing it on a tripod. It consists of a standard smc pentax

A 1:2 50MM LENS which was fixed to a tube using a normal PK fit

coupling. The tube looks at first as though it may be an ordinary

macro tube, but on closer inspection it tapers off at the opposite end

to the PK coupling and ends with an M42 coupling. Hence, when fitted

together it can be screwed into an M42 camera. Yet it surely can't be

an M42 body to PK lens coupler, as these are said to be an

impossibility. Nevertheless, I've tried it on one of my SP1000s and

predictably it's totally out of focus - I haven't yet tried it as an

M42 macro as I simply don't believe this can possibly be the answer.

The final clue is a small conical 'knob' which sits near the top

towards the PK fit where it controls a single pin. As I've said, there

is nothing that suggests that it has anything to do with a tripod.

The lens alone was a great bargain for 8 pounds stirling - in perfect

condition. I think perhaps a lack of explanation put a lot of

potential bidders off.

Anyone have any ideas?

 

Many thanks.

 

Graham.

[unca mikey]

I have no earthly idea, but am intrigued by your description. Could you post a picture somewhere so we can see it?

[stemked]

"Yet it surely can't be an M42 body to PK lens coupler, as these are said to be an impossibility"

 

Not true. There is a teleconvertor made to use K-mount lenses on screw mount bodies. They are expensive and of questionable quality and value, but they do exist.

 

It sounds to me like someone descided to adapt his/her K-mounts to a screw mount body. Rather than a teleconvertor it sounds like they were using it for macro work. So it should still work it just won't focus all that far, certainly not out to infinity.

[graham_powell1]

I've tried using it as a macro now, but still it seems incapable of focussing on anything. It really has me puzzled, it's a well made piece of kit that doesn't have any apparent use. I wish I were able to post Ebay's picture of it here, but I fear that I would be in breach of copyright.

 

I'm afraid that I've kicked out Windows XP Pro and replaced it with Suse 9.3 Linux, which although much better for most projects, refuses to recognise my scanner.

 

As I find digital imaging a tedious bore (eventually it seems as though every part of life will 'have' to go through a computer) I don't need the computer for digital imaging. If I should be mistaken about my copyright concern, please let me know and I will upload Ebay's image.

[graham_powell1]

Problem solved! In desparation I decided to get in touch with the seller. Aparently 'it was removed from a broken CCTV camera, an old style fixed focus fixed position mount.' Why it was put on the end of a Pentax A 50mm lens I'm afraid has to remain a mystery. It's strange the way one end is PK and the other M42 anyway. Anybody know about CCTV cameras?

[tonyc]

Hi I do know that many CCTV cameras used M42 mounts (other mounts include 'C' mount, for example. It could be that due to the very small sensor (CMOS probably) in CCTV cameras (typicaly a third of an inch or smaller), and the depth that the sensor was positioned in the CCTV camera, the 50mm lens had to be positioned further away from the camera body than on a 35mm camera (distance from focal plane, for a useable portion of the lens's imaging circle to have been used. It is possible that a CCTV installer obtained this 50mm lens at a much cheaper price than a 'dedicated'CCTV lens, plus the low light capabiity of this lens would have been a bonus in a dark setting.

 

Pentax still lenses have seen greater use than one might expect in motion picture film cameras also. Regards, Tony.