[Skodadriver]

I received a TOKUNON 135mm F3.2 lens bought at auction and listed as a Pentax mount. Unfortunately it is smaller than a Pentax K mount (and the registration distance may not be the same, it seems to project a little further than a K mount T-mount).
Can someone let me know what camera mount this is? The removable mount screws on but it is not M42
I swapped the internals of a T-mount that I had in K mount and tried the lens and optically it seems fine, where it is locked at 1.7 m on the focus ring is about how far I had to be to get focus.


The focus barrel is locked solid and the aperture ring is intermittently very stiff, would this be a grease problem?

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Last edited by Skodadriver; 01-20-2019 at 04:54 AM.

[Not a Number]

It looks like the adapter is just a T-mount. If so I doesn't matter what the bayonet is for.

You said your K-mount T-adapter fits? Does the adapter from the lens fit on your other T-mount lenses?

An intermittent stiff aperture rings (looks like a pre-set lens) would most likely mean the grease is dried out.

A locked focusing ring is not a good sign. Maybe put the lens out in the sun for a few minutes to warm up and see if it loosens a bit. I'd send the lens back unless it was sold as is or the locked focus was noted in the listing.

[BigMackCam]

My best guess would be that the lens is T-mount, requiring an adapter to the relevant camera. The adapter that came with the lens looks, to me, like an Exacta mount. You'd need to replace that with a T-to-K-mount to use the lens on your Pentax camera.

The seized focus ring is most likely due to congealed / dried out lubrication. The diaphragm could be resistant due to congealed lubrication on the blades or elsewhere in the diaphragm mechanism. Sounds like it needs stripping down, cleaning and re-lubricating. Probably a relatively simple job, but rather time-consuming.

[Skodadriver]

My best guess would be that the lens is T-mount, requiring an adapter to the relevant camera. The adapter that came with the lens looks, to me, like an Exacta mount. You'd need to replace that with a T-to-K-mount to use the lens on your Pentax camera.

The seized focus ring is most likely due to congealed / dried out lubrication. The diaphragm could be resistant due to congealed lubrication on the blades or elsewhere in the diaphragm mechanism. Sounds like it needs stripping down, cleaning and re-lubricating. Probably a relatively simple job, but rather time-consuming.

Thank you, it certainly does look like an Exacta bayonet.
The lens has many blades so might be worth attempting to clean and re-grease, I have some JIS screwdrivers which I believe you recommended to me, however I have trembly hands and my eyesight is not the best, the tiny screws look like they might be easily lost. Still nothing ventured, nothing gained.

---------- Post added 07-18-18 at 01:05 PM ----------

It looks like the adapter is just a T-mount. If so I doesn't matter what the bayonet is for.

You said your K-mount T-adapter fits? Does the adapter from the lens fit on your other T-mount lenses?

An intermittent stiff aperture rings (looks like a pre-set lens) would most likely mean the grease is dried out.

A locked focusing ring is not a good sign. Maybe put the lens out in the sun for a few minutes to warm up and see if it loosens a bit. I'd send the lens back unless it was sold as is or the locked focus was noted in the listing.

The lens was listed as excellent but obviously is not. The seller has promised to refund the cost (minus P&P) so I am awaiting that.
I shall try leaving the lens in the sun, thank you for the suggestion.

[BigMackCam]

Thank you, it certainly does look like an Exacta bayonet.

You're welcome

The lens has many blades so might be worth attempting to clean and re-grease, I have some JIS screwdrivers which I believe you recommended to me, however I have trembly hands and my eyesight is not the best, the tiny screws look like they might be easily lost. Still nothing ventured, nothing gained.

Regarding the trembling hands, it's not a regular problem for me, but it does happen sometimes. I'm not for one minute recommending self-medication (ahem!), but one small glass of wine on the evening you're going to do the job might work wonders. It does for me on those rare occasions, and my Dad - who suffers from benign essential tremor - is rock steady after one Bacardi and Coke

Take it slowly... and have some containers ready for the screws and other small components (I use M39 or M42 rear lens caps). Do a little bit at a time, and take plenty of breaks. Take plenty of photos with your phone or a compact camera as you work, so you know how things looked before and after you've disassembled things. When you separate threaded sections, do it slowly and mark the points at which they separated on both components, using the edge of a flat-bladed screwdriver to carve a small notch into a non-visible area. When cleaning away the old grease, wooden cocktail sticks are perfect for getting deep-seated congealed lubricant out of threads. Use a toothbrush and washing up liquid with warm water to fully clean the threads after you've got the thick of the grease cleaned off.

Good luck!

[Not a Number]

I shall try leaving the lens in the sun, thank you for the suggestion.

Just long enough to feel warm to the touch. Don't bake it for hours. Warming up the grease will not be a permanent solution but will just allow you to see if the grease is hardened up or there is something more serious mechanically going on.