[Dean31]

I have bought one of these lenses and it doesn't fit my Pentax Kx. I'm having trouble finding what mount this lens is so I can buy an adapter for it. Does anyone know what mount I need for this lens to fit my Kx? In lens review section I saw where someone said I need a 2x teleconverter with Kx mount. Is there another option?

I have the Tokina make from about 1983 if that helps. If it turns out this lens isn't worth finding an adapter for, that's ok too....all input apprecited.

Thanks!

[Adam]

You should post a picture of the lens mount and we'll be able to tell you.

If it doesn't fit your camera, though, you should probably return it and get one with a K mount (that's what the Pentax-compatible mount is called) instead.

[RioRico]

Vivitar (and Tokina) sold lenses for many different mounts so the brand names don't help in identifying a lens. Yes, we need pictures of the mount. Unless it's an M42 screwmount lens, you probably won't want (or even find!) any adapters. Optical adapters exist for some mounts but they will reduce image quality. Such adapters act as short telextenders; they increase the focal length and shrink the maximum aperture. They also may cost more than the lens is worth. But we need to see pictures before we can offer any meaningful advice.

[Dean31]

Thanks Adam/Rico....I can seemingly get it to fit on, but it doesn't turn and lock at all. I'll look silly if there is a locking mechanism or something I need to open/close to get it to snap, but o well, that's why I'm here

1st time user a Flickr link, I have three pics of the mount posted. vivitar_mount | Flickr - Photo Sharing!

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Last edited by Dean31; 12-03-2011 at 01:38 PM. Reason: Adding Rico to edit

[RioRico]

1st time user a Flickr link, I have three pics of the mount posted. vivitar_mount | Flickr - Photo Sharing!

That is an Olympus OM mount. The giveaway is the existence of pushbuttons on the sides of the lens base -- one is lock-release, the other is aperture stop-down. An OM lens is very easy to modify for Pentax PK mount if you don't mind using a Dremel metal-cutting blade. I've chopped a few.

But that lens is on the heavy side. I am reluctant (paranoid) to chop long heavy lenses. Possibilities:

1) Make the Dremel cuts and hope the mount remains secure.
2) Replace the base plate with either a PK-M42 adapter or the base from a PK lens.
3) Sell the OM lens and find a PK version. They are neither rare nor costly.

I recommend #3. Unless you need some lens-modding practice, it's not really worth screwing around with. Cheers!

[Dean31]

To use the dremel modification method....I cut off the lock-release pushbutton that is protruding? I assume this is what is preventing the lens from turning into place? (I realize it won't lock on if I do this).

[RioRico]

To use the dremel modification method....I cut off the lock-release pushbutton that is protruding? I assume this is what is preventing the lens from turning into place? (I realize it won't lock on if I do this).

NO! The problem with OM (and similar C/Y) mounts is that the bayonet flags are just a smidge too thick to fit under the PK mount lugs. I use the Dremel blade to shave away a little of the flag metal, to taper the flags so they WILL force-fit. I then cut a small slot in the lens base for the PK locking pin to engage, for a more secure fit.

The OM lock-release button is not in the way of anything. The OM stop-down button is another matter. As-is, a modded OM lens would only work on the PK camera with the lens aperture wide open. Two options here: 1) unscrew the lens base, remove the stop-down button, and jam its spring to hold the iris closed to whatever aperture setting you use. Or 2), jam the button down -- a bit of metal tape works.

With the bayonet flags tapered, the locking slot cut, and the stop-down button taped down, the lens can still be used on OM cameras -- just remove the tape! This is about as non-destructive a mod as I can devise.

I have a few posts here dealing with such lens mods. I need to compile them into an article, yes I do. But heed this: Before trying any lens-chopping, buy a set of ultra-cheap PK macro tubes, about US$7 shipped from China. The mount section serves as a great test-bed and inspection port. Set an OM or C/Y or Nikon or other lens on it, and you can see exactly what parts of the lens and mount foul each other, thus what and how much to cut.