Forgot Password
Pentax Camera Forums Home
 

Reply
Show Printable Version Search this Thread
01-16-2009, 08:58 AM   #1
Veteran Member
ytterbium's Avatar

Join Date: Jan 2008
Posts: 1,076
SMC Takumar 55/1.8 Odd pin.

Just received my Takumar. After having a brief look at it, realized i couldn't flip the aperture switch from A to M. When having a closer look, saw an odd pin, i have not seen on any other of my m42 lenses (seen in attached picture).
As i found out, by pushing it fully in, it allows aperture setting to be changed to manual. When releasing pin, switch can be moved to auto, but then it is locked again.
When mounted on digital camera using adapter, the adapter pushes it, as m42 camera mount would do, so then the A/M switch operation is as usual.

How exactly it is called. Could not find much in Google, since most results referred to stop down pin, only this:
What purpose has it?
Is there anything i must know when using lens with such a pin?
Such as, the pin can stuck in screws on a real m42 body (since the adapter is flat, but my Zenit-E has screws on its mount surface), as in here:
http://flickr.com/photos/noorhilmi/2772729834/

Btw, fantastic lens... as i don't shoot (photograph) people much couldn't justify 300$ just for a AF screw and new, plastic body. Since i lowed how my F50/1.7 performed, had to get something similar. So got this for 40$, and i love it.


Last edited by ytterbium; 05-11-2009 at 11:10 AM.
01-16-2009, 09:22 AM   #2
Veteran Member
Mike Cash's Avatar

Join Date: Jan 2007
Location: Japan
Photos: Gallery
Posts: 6,952
As best I can figure out, the purpose is to lock the switch in the auto position on the three Spotmatic bodies which are capable of open-aperture metering. That's just a guess, though. It may do the same on all Spotmatics with light meters for all I know.
01-16-2009, 09:28 AM   #3
Veteran Member
ytterbium's Avatar

Join Date: Jan 2008
Posts: 1,076
Original Poster
This means, there must be a gap on the mount on those bodies, to release the pin, when lens is mounted. Also it must have smooth transition, to not lock that pin. And no screws, as in here:
http://www.pacificrimcamera.com/images/110150.jpg
Wonder if it can be removed/locked down..
01-16-2009, 09:39 AM   #4
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,399
my 35mm F2 is the same, and it prevents going back into auto mode if not mounted on a body.

01-16-2009, 09:40 AM - 1 Like   #5
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,846
The pin is there to reduce the price of these lenses on eBay. You'll see an auction describing an SMC Takumar lens as being perfect except for the A/M switch being stuck on A. Bid in these lenses, because many others will skip them.

The pin was introduced when Pentax introduced cameras with open aperture metering, like the K mount does today. Those cameras (Spotmatic F, ES, ESII) have a slightly modified mount with an extra machined ledge that incorporates this pin, allowing it to stay extended. Once the new user switches his lens to Auto, the switch stays locked in Auto, and the camera can use open aperture metering. If the lens is used on an older camera, the pin will be pressed in and the lens will work like older lenses. I think the number of users who would complain about a stuck A/M switch would equal the number of users complaining about defective open-apeture metering, but that's what Pentax chose.

The pin is mostly an obstruction today, catching people off guard. Sometimes you'll see that pin removed, not worth it IMO. I've seen them stuck in by corrosion or dirt.
01-16-2009, 09:49 AM   #6
Veteran Member
troyz's Avatar

Join Date: May 2008
Posts: 389
QuoteOriginally posted by ytterbium Quote
This means, there must be a gap on the mount on those bodies, to release the pin, when lens is mounted. Also it must have smooth transition, to not lock that pin.
Taka a look at:

Screwmounts

There's a groove machined into the lens mount next to the threads on the spotmatic II that prevents actuation of the camera type sensor pin.
01-16-2009, 09:54 AM   #7
Veteran Member
ytterbium's Avatar

Join Date: Jan 2008
Posts: 1,076
Original Poster
Thankyou all very much, then it seems that there is nothing more to it than that.
So ill just try to remove it, so it can be safely mounted on my Zenit-E. Just hope this lens has a simple mount attachment (not like F50/1.7 ejecting contact pins in random directions upon mount removal).
01-16-2009, 09:58 AM   #8
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,399
QuoteOriginally posted by ytterbium Quote
Thankyou all very much, then it seems that there is nothing more to it than that.
So ill just try to remove it, so it can be safely mounted on my Zenit-E. Just hope this lens has a simple mount attachment (not like F50/1.7 ejecting contact pins in random directions upon mount removal).
why go to that trouble, just put the lens cap back on to put it in auto

01-16-2009, 10:08 AM   #9
Veteran Member
Nesster's Avatar

Join Date: Oct 2006
Location: NJ USA
Photos: Gallery
Posts: 13,047
FWIW ~ I've mounted SMC Takumars on a variety of cameras and adaptors, never with any problems with things getting stuck: SP1000, Fuji ST605, Yash Electro-X, all K mount cameras with either Bower or Pentax adapters, the Pentax M42 bellows, Vivitar extension tubes.

I did think one of the 50/1.4's I got via goodwill was broken until I found this pin. It's easy enough to push it in with a fingernail when the lens isn't mounted. When it is, on anything but the particular Pentax cameras with open aperture metering, there's no issue (see above list) with moving between M and A.

I would bet the lens is safe on the Zenit. Breaking the mount IMHO reduces the value and usability of the lens. I wouldn't touch it.
01-16-2009, 10:21 AM   #10
Veteran Member
ytterbium's Avatar

Join Date: Jan 2008
Posts: 1,076
Original Poster
Have you used soviet stuff.. well it is made to brake itself, or break something that comes close to it..
As for pushing with fingernail, when in M setting, it doesnt stay in. So if i push it in, switch to M, the pin still stays out and when i will mount it on my Zenit, it will stuck in first screw it meets close enough.
I've modified stop-down pins, to stay in pushed position (add a ring around it, wich keeps it inside), i bet the same or similar can be done to this one, without any damage or actual part removal from lens.
01-16-2009, 10:24 AM   #11
Pentaxian
Just1MoreDave's Avatar

Join Date: Feb 2007
Location: Aurora, CO
Photos: Gallery | Albums
Posts: 4,846
QuoteOriginally posted by ytterbium Quote
Thankyou all very much, then it seems that there is nothing more to it than that.
So ill just try to remove it, so it can be safely mounted on my Zenit-E. Just hope this lens has a simple mount attachment (not like F50/1.7 ejecting contact pins in random directions upon mount removal).
The lens mount is very simple. It's solid aluminum. All you have to do is take everything else off, then there's the mount. I have pictures somewhere if you need help.

I would seriously consider super glue unless the lens has another issue to fix. Value is not that big an issue with a 55/1.8; usability is IMO improved since the pin is designed to get in your way. If you do take this lens apart, reglue the distance scale.
01-16-2009, 10:46 AM   #12
Veteran Member
ytterbium's Avatar

Join Date: Jan 2008
Posts: 1,076
Original Poster
Btw, since talkng about mounts... for AF Trap and correct exposure, it is suggested, to sand off some paint on lens over the A/* contact. But that contact is recessed into mount so i dont see, plain paint removal shorting it to mount, or it is enough to short any of the pins, for this to work?
01-16-2009, 11:17 AM   #13
Pentaxian
Lowell Goudge's Avatar

Join Date: Jan 2007
Location: Toronto
Photos: Gallery | Albums
Posts: 15,399
QuoteOriginally posted by ytterbium Quote
Btw, since talkng about mounts... for AF Trap and correct exposure, it is suggested, to sand off some paint on lens over the A/* contact. But that contact is recessed into mount so i dont see, plain paint removal shorting it to mount, or it is enough to short any of the pins, for this to work?
it's not the A pin, but the focus information pin, at the last position away from the lens locking pin.

This will allow focus indication and trap focusing, IF the mount is wide enough to cover the pin.
01-16-2009, 03:38 PM   #14
Veteran Member
Mike Cash's Avatar

Join Date: Jan 2007
Location: Japan
Photos: Gallery
Posts: 6,952
The 55/1.8 doesn't cover the pins anyway, so there is no point to sanding the mount.
01-17-2009, 01:39 PM   #15
Veteran Member
ytterbium's Avatar

Join Date: Jan 2008
Posts: 1,076
Original Poster
QuoteOriginally posted by Lowell Goudge Quote
it's not the A pin, but the focus information pin, at the last position away from the lens locking pin.

This will allow focus indication and trap focusing, IF the mount is wide enough to cover the pin.
Wierd, i recall reading somewhere it was the A/* pin. I even tested, shorting it with a screwdriver, and the Trap AF started working as well as metering too.
And is it safe to short digital data pin?
Since A pin was designed to be shorted (when you put a lens with a ring in A position, it shorts it), but Data pin might have some larger current limit available, to supply lens electronics. But theoretically it should be designed to be shorted too, because it happens every time you're screwing your (even DA) lens on... unless there was a point in manual that you should turn the camera off, when changing lenses...was there (i haven't red all manual)?
Reply

Bookmarks
  • Submit Thread to Facebook Facebook
  • Submit Thread to Twitter Twitter
  • Submit Thread to Digg Digg
Tags - Make this thread easier to find by adding keywords to it!
adapter, aperture, body, camera, k-mount, m42, pentax lens, pin, screws, slr lens, smc takumar, switch, takumar
Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
SMC Takumar VS Super-Multi-Coated Takumar 50/1.4 RolloR Pentax SLR Lens Discussion 5 05-08-2010 06:38 AM
Super Takumar vs SMC Takumar Coatings drewdlephone Pentax SLR Lens Discussion 20 12-31-2009 04:40 PM
have you ever compared the Takumar 85mm 1,9 with the SMC Takumar 1,8??? 1,8 & 1,4? beegee Pentax SLR Lens Discussion 5 02-14-2009 07:31 PM



All times are GMT -7. The time now is 12:29 AM. | See also: NikonForums.com, CanonForums.com part of our network of photo forums!
  • Red (Default)
  • Green
  • Gray
  • Dark
  • Dark Yellow
  • Dark Blue
  • Old Red
  • Old Green
  • Old Gray
  • Dial-Up Style
Hello! It's great to see you back on the forum! Have you considered joining the community?
register
Creating a FREE ACCOUNT takes under a minute, removes ads, and lets you post! [Dismiss]
Top