Why won’t my Pentax K-mount to Canon EF adapter lock onto my Pentax lenses?
Asked 2/25/2015
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2 answers
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I’m trying to use older Pentax K-mount lenses on a Canon Rebel T2i with a PK-to-EF adapter. My Pentax 50mm f/2 and Vivitar 28mm f/2.8 both mount normally on a Pentax K1000, but the adapter will not rotate fully into place on either lens. It starts to engage, then binds before the retaining spring can click over the ridge and lock. I’ve aligned the dots and tried pressing the spring, but it still won’t seat. Is there a trick to mounting these adapters, or is the adapter likely defective or out of spec?
Originally by Photography Stack Exchange contributor. Source · Licensed CC BY-SA 4.0
Photography Stack Exchange contributor
11y ago
2 Answers
4
Did you see the following review on the Amazon page for the product you linked to?
As noted by other people who have bought this adapter, there are issues with its ability to securely mount the Pentax lens. After doing some cross-referencing with similar adapters, it is obvious that the retaining spring is on wrong! Someone had one job to do…. Spring needs to be taken off, bent back in the opposite direction and reinstalled with the slot in the spring toward the camera
Originally by user4859. Source · Licensed CC BY-SA 4.0
user4859
11y ago
0
Generated from our catalog & community — verify before relying on it.
If both lenses mount correctly on the Pentax K1000, the problem is most likely the adapter, not your lenses or technique.
From the community replies, these PK-to-EF adapters can have a misinstalled or misaligned retaining spring. A common issue is that the spring is fitted the wrong way, or positioned slightly too far so it jams before the adapter can rotate and lock. Pentax-compatible bayonet flange dimensions can also vary slightly between lenses, so a poorly toleranced adapter may bind on some or all lenses.
What to check:
- Inspect the retaining spring orientation; it may be reversed.
- If the spring is adjustable with screws/slots, loosen and reposition it slightly.
- If the adapter still jams on multiple lenses, it is likely defective or out of spec.
Since both of your lenses fit the Pentax body, a good adapter should mount without forcing. Don’t keep twisting hard, since that can damage the lens mount. The practical fix is to return or replace the adapter with a better-made PK-to-EF adapter.
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UniqueBot
AI11y ago
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