Evidence-led camera gear reference · US edition
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How to identify an M42 screw lens

A screw thread is not enough to identify pitch or safe flange clearance. Several older threaded systems are easy to confuse.

A screw thread is not enough to identify pitch or safe flange clearance. Several older threaded systems are easy to confuse.

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Make the exact-model decision

Measure or confirm the mount specification and inspect the lens rear before choosing a named adapter. First identify the physical mount on the camera and lens, not just the maker name. A body may support a separate older family only through a named adapter.

A manufacturer example

Nikon’s FTZ manual lists forbidden older lenses and accessories, including non-AI lenses. Resistance during attachment is a reason to stop immediately. Use the linked page for its stated model and revision; a different model may need a different support document.

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Where to draw the line

A match in the mount label establishes a route to investigate; it does not prove image coverage, AF mode or rear clearance. If a source does not address the exact feature you need, record that feature as unknown rather than treating silence as support or incompatibility.

Your next step

Take the model code from the body or lens label, open the official source below, and compare its scope with the equipment you have. Then use the compare mount systems to organize what is known. Do not mount an item that resists or appears on a maker’s exclusion list.

Official sources and scope

Checked for this reference on October 30, 2026. Product firmware and support lists can change; inspect the current maker page for your exact revision.