T-mount to L-Mount adapter compatibility

T-mount is the one entry in this matrix that is not really a camera mount at all. It is a lens-side interface — the M42 × 0.75 thread Tamron introduced in 1957 and standardised as T-2 in 1962 — with a fixed 55 mm spacing from the thread shoulder to the focal plane. The lens carries no bayonet of its own; it screws into a body-specific T-X adapter ring, and it is that ring which carries the camera mount. For an L-Mount body you fit a T-L ring: the lens threads into the front, the L bayonet sits on the back, and because the L-Mount flange is 20 mm the ring is built as a roughly 35 mm tube that makes up the difference. That leaves a full 35.0 mm of clearance, so infinity focus is never in doubt — the optics always sit at their designed 55 mm regardless of body. The L-Mount's wide 51.6 mm throat helps too, swallowing the bulky rear cells of a catadioptric lens without the optics fouling the ring. And here the one-lens-many-bodies economy goes a step further than usual: because L-Mount is a shared alliance standard, a single T-L ring is literally a one-ring-many-brands key.

What you actually mount is all long glass, because that is what T-mount has always been for. The Vivitar 500 mm f/8 Mirror and the Samyang 800 mm f/8 Mirror MC are catadioptric (mirror) lenses, astonishingly compact for their reach because the light path folds back on itself, and the Soligor 400 mm f/6.3 Tele is a conventional refractive long lens. None of them autofocuses; all three were built as budget reach for wildlife, the Moon and the Sun. L-Mount is a distinctive destination because it is not one company's mount but the L-Mount Alliance — the standard Leica, Panasonic and Sigma jointly back — so the exact same generic mechanical T-L ring from Fotodiox, K&F Concept or Gobe threads your mirror lenses onto a Panasonic Lumix S5 II or S1R II, a Sigma fp or fp L, and a Leica SL2 or SL3 without buying a different adapter for each. A photographer who owns bodies from two of those brands, or who rents across the alliance, gets the most mileage of any T destination from a single cheap ring — and that ring costs less than a memory card.

The verdict reads Mechanical · MF · no IS · Ap. ring, and every term is honest for this glass — with one nuance the badge cannot show. Focus is manual, set on the lens barrel and confirmed through the body's focus peaking and magnified live view, because there are no electrical contacts anywhere in a T-mount lens or its ring, so nothing passes EXIF, aperture commands or stabilisation data to the body. 'Ap. ring' is true of the refractive Soligor 400 mm f/6.3, which carries a real preset diaphragm — dial the working f-stop on one ring, then a second ring stops down in a quick turn — but it is not true of the two mirror lenses. A catadioptric design has no iris at all: the Vivitar 500 mm and Samyang 800 mm are fixed at f/8, so you set exposure with shutter, ISO and screw-in or rear drop-in ND filters, and you accept the signature ring-shaped 'donut' highlights a mirror lens renders out of focus.

Stabilisation is available on the bodies that have it, but you have to ask for it — and on the L-Mount the answer is not uniform across the alliance, which is worth knowing before you buy. Panasonic's full-frame Lumix S bodies (S1, S1R, S5, S5 II, S1R II) and Leica's SL2, SL2-S and SL3 carry sensor-shift IBIS; you engage it with a manual lens by registering the focal length by hand in the body's stabiliser menu — 500 mm for the Vivitar, 800 mm for the Samyang — after which it helps tame shake, though at those lengths a monopod or tripod stays part of the kit. Sigma's fp and fp L, by contrast, have no in-body stabilisation at all and lean entirely on support (the original 2015 Leica SL likewise predates IBIS). Image circle is the easy part: all three lenses cover full-frame, so they shoot clean edge to edge on any of the alliance's full-frame bodies, while an APS-C L body — or a full-frame body shooting in its APS-C crop mode — reads the centre and applies a 1.5× crop, turning the Vivitar 500 mm into a 750 mm-equivalent and the Samyang 800 mm into a 1200 mm-equivalent.

The honest summary: T-mount → L-Mount is the budget-reach and amateur-astronomy route for anyone in the Leica–Panasonic–Sigma camp, not a precision-AF or cine path. Fit a generic mechanical T-L ring — and note that the very same ring serves a Panasonic Lumix S, a Sigma fp and a Leica SL, the rare T destination where one adapter spans three brands — focus by hand on the EVF, accept fixed f/8 and donut bokeh on the Vivitar 500 and Samyang 800 mirror lenses, reach for the Soligor 400's preset ring when you want a conventional rendering, and register the focal length in the stabiliser menu on an IBIS body (a Panasonic S or a Leica SL2/SL3) so it helps at the long end. And because T-mount is the de-facto standard for astronomy optics, the same T-L ring threads straight onto a telescope's focuser for prime-focus lunar, solar and deep-sky work — so one inexpensive ring serves both your mirror lenses and your scope across every body you own in the alliance.