I have an old Ricoh 35 mm SLR camera. It uses a Screw mount lens system as oppose to other 35mm cameras that adopted the Bayonet mount system otherwise know as T-mount. I am looking for a conversion ring that will allow my camera to accept T-mount lenses since there are not many Screw mount lenses out their anymore. I have looked on line and have found only converters that will allow me to use cameras with T-mounts to use screw mount lenses but nothing that will fit my needs. Am I wasting my time or are there converters out there that will meet my needs?

  • \$\begingroup\$ T-mount has 42mm x 0.75mm pitched threads. Your Ricoh probably uses the M42 mount, which has threads with a pitch of 1.0mm. T-mount adapters have a receiver on the front that accepts the 42mm x 0.75mm T-threads and a bayonet on the back that attaches to a specific bayonet mount system. \$\endgroup\$
    – Michael C
    Commented Jul 10, 2017 at 17:57
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    \$\begingroup\$ What specific Ricoh model do you have? \$\endgroup\$
    – Michael C
    Commented Jul 10, 2017 at 18:00
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    \$\begingroup\$ I'm voting to close this as unclear because of the T-mount confusion. I suspect as does @xiota that you mean "K-mount", but… maybe not? \$\endgroup\$
    – mattdm
    Commented Sep 5, 2018 at 13:34

1 Answer 1


M42 vs T-mount vs K-mount

It seems you may be confusing M42, T-mount, and bayonet mounts. Per comment by Michael Clark:

T-mount has 42mm x 0.75mm pitched threads. Your Ricoh probably uses the M42 mount, which has threads with a pitch of 1.0mm.

Ricoh switched to using the Pentax K-mount in 1977.

Ricoh Cameras

The following cameras use the M42 mount:

The following cameras use K-mount:

Adapting Lenses

For issues concerning the use of lens adapters, see Can I use lens brand X on interchangeable lens camera brand Y? In particular, Registration Distance / Flange Focal Distance will be a problem.

The M42 screw mount has a registration distance of 45.46mm. Most commonly-used modern mounts have a shorter registration distance. A notable exception is the Nikon F mount, which has a registration distance of 46.50mm.

While there is an adapter from F-mount to M42 (eBay/Amazon), it appears to not be thin enough to maintain infinity focus. An adapter with a corrective lens would be required.


Many old M42 lenses are available with various levels of quality or interesting characteristics. What do you hope to gain by seeking to use a new lens with an old body?


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