takumar 50mm 1.4 - aperture/focus "stuck"?

dharmaone · Joined: 07 Jun 2009 Posts: 5

Hi all,

I have a 50mm 1.4 super takumar that I really like.

However I think it could use a bit of attention - unless I'm shooting wide open, turning the focus clockwise ring also seems to open up the aperture - I have to slightly turn the focus back to get the aperture back to where it was set.

It's as if the aperture and the focus controls are somehow linked or "stuck" together when turning focus clockwise.

Anyone come across a similar issue before? Do I have to open up the lens to fix it?

Many thanks!

Lightshow · Joined: 04 Nov 2011 Posts: 3670 Location: Calgary

Sounds like something is wrong, does the aperture open and close easily by pressing the pin?
Sounds like the optical block is rotating when turning the focus ring, so something could be loose, so keep an eye out for loose screws etc...
Opening it up is easy, unscrew the name ring, 3 screws hold the filter ring, 3 more hold the optical block in, that will give you access to everything, there should be a lever on the optical block that works the aperture blades, it should move easily, on the body, pressing the pin should cause a lever to move inside, now what does rotating the focus ring do?

Pentax did make a few changes through the years, so my description may be off a bit.
Take pics every time you remove something, Post pics if you get lost or need advise,
all else fails I'd be willing to see what I can do, all you have to do is cover postage.
Good luck.

dharmaone · Joined: 07 Jun 2009 Posts: 5

Thanks for the tips lightshow, you are very kind. People like you are what the internet is all about!

I was feeling courageous tonight and took the lens apart. this guide was a big help - http://retinarescue.com/pentax50mmf1.4.html

Turns out there was a loose screw inside the lens, had to take the whole thing apart to get to it though!

My respect for the Japanese has doubled.. it's pretty clever how these things are put together

Now all I need to do is leave the lens in the sun for a week or so for the UV to get rid of the yellowing.

Should I be worried about the thorium? I have a feeling I'll be using this lens lot again now that it's fully working

Mike Deep · Joined: 25 Oct 2008 Posts: 316 Location: Upstate New York

I had a similar problem with my 8-element that was preventing me from using it. Any time the focus ring was turned, the aperture would open or close slightly.

I only got around to fixing it the other day, once I had the proper tools: a rubber name ring remover and spanner wrench. The instructions linked above are very useful and this is not a difficult lens to work on with the right tools.

Once the lens was completely apart, the problem was revealed to be the screws in the very last picture in those instructions: http://retinarescue.com/images/pentax509.jpg
All four had become loose and were allowing the barrel to have some back and forth play.

philslizzy · Joined: 07 Aug 2012 Posts: 4749 Location: Cheshire, England

I have the same problem with an M42 Meritar. Almost impossible to use as it is.