Irix 150mm macro and 1.7x AF adapter.
Posted 30/03/2023 - 21:21
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I have the 11mm which has the same issue with its mount. However the Pentaxforums test of the later 45mm has a picture of the mount which shows Irix have now added the missing long slot. Whether Irix are now fitting this updated mount to the earlier lenses I've no idea.
Steve
Steve
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2584 posts
16 years
South Dorset
The current K-mount on a lens has a long slot running along part of the inner edge of the mount face. It is needed to accommodate a tab (stop down coupler) on whatever is to be attached to the lens (camera, tube etc.). The Irix does not have that slot. The 1.7 AF adapter does have the tab. The lack of a slot prevents the adapter attaching to the lens. The tab does not protrude very far into the slot so the adapter almost attaches to the Irix, but 'almost' is enough to stop the bayonet from engaging. I confirmed it with an old set of extension tubes. A tube with the tab does not attach to the Irix, a tube without the tab (removed for another reason) does attach.
What is somewhat annoying is that the slot is only needed for back-compatibility with cameras and attachments that pre-date the 'crippled K-mount' which was introduced on late film cameras (removing the the stop-down coupling tab is what 'crippled' the mount, aperture then had to be set on the camera rather than lens). The Irix will therefore attach to any Pentax digital camera plus the later film cameras but not to the earlier film cameras and associated equipment such as the 1.7x AF adapter. So the Irix does attach to my digital cameras and film *ist but not to the film P30. And just for completeness, the Pentax 1.4 TC does not have a stop-down coupler tab so does attach to the Irix.
If I were bold and competent, I might try to remove the tab from the 1.7x AF adapter. But I am neither so the adapter remains unmolested and will never be attached to the Irix.
Steve