Sigma XQ Scalematic 135mm f/1.8 Manual Focus Portrait Lens
Offered here is an unusual Sigma XQ Scalematic 135mm f/1.8 manual-focus prime lens from the 1970s, fitted with an M42-thread T2 mount.
The combination of a 135mm focal length and very fast f/1.8 maximum aperture makes this a distinctive portrait lens, capable of producing shallow depth of field and strong background separation. It has the substantial metal construction associated with Sigma's XQ range and uses a large 77mm filter thread.
The lens was originally designed for Sigma's YS interchangeable mount system. Genuine YS mounts are now relatively difficult to find, so this example has been fitted with a T2 adapter carrying an M42 thread.
Mount and Aperture Operation
Because the fitted T2 mount does not reproduce the original Sigma YS automatic-diaphragm linkage, the aperture must be operated manually. A small shim has been fitted so that the aperture-actuating pin remains engaged and the diaphragm can be controlled from the aperture ring.
The aperture ring is somewhat rough in operation and can occasionally stick part-way through its travel. It can still be worked across the full aperture range with gentle manipulation, and the diaphragm itself opens and closes correctly.
Optical and Mechanical Condition
| Area | Condition |
|---|---|
| Front and rear glass | No scratches observed |
| Cleaning marks | None observed |
| Fungus | One very small central spot |
| Focus movement | Smooth in operation |
| Focus-ring grip | Original rubber or vinyl grip missing |
| Aperture ring | Occasionally stiff or notchy and may require gentle persuasion |
| Aperture blades | No oil observed |
| Diaphragm | Operating correctly |
| Filter thread | Undamaged |
The tiny fungus spot is disclosed for completeness. It is not expected to have any visible effect on photographs, but buyers should study the close-up images carefully and form their own judgement.
The missing focus-ring grip does not prevent use of the lens. A simple temporary grip can be improvised with suitable rubber bands, or a more permanent replacement could be fabricated by the buyer.
Use on Modern Cameras
Although supplied with an M42-thread T2 mount, this lens is likely to be of greatest interest to photographers adapting classic manual-focus lenses for use on modern digital cameras.
With the appropriate adapter, it may be used on many mirrorless systems including Sony E, Canon RF, Nikon Z, Fujifilm X, Micro Four Thirds and Leica L. It may also be adapted to DSLR systems, although some combinations, particularly Nikon F, may require an adapter containing corrective optics if infinity focus is required.
All focusing and aperture control will be manual, and buyers should confirm flange distance and adapter compatibility for their own camera before purchase.
Rendering and Practical Use
The Sigma XQ 135mm f/1.8 has developed a following among users of vintage manual-focus optics because of its unusually fast aperture, strong subject isolation and attractive portrait rendering.
As with many fast telephoto lenses of this period, contrast can be improved and flare reduced by using a deep 77mm lens hood. No hood is included.
The lens is not a perfect collector-grade example, but it remains a usable and unusual fast portrait lens with considerable character. It may suit portrait photography, low-light work, creative digital photography, video production and photographers experimenting with adapted vintage lenses.
Collecting Interest
This lens may also appeal to collectors of Sigma XQ equipment, Sigma YS interchangeable-mount lenses and 1970s Japanese photographic optics. The 135mm f/1.8 specification is unusual, and the lens represents an interesting stage in the development of fast third-party portrait lenses before autofocus became standard.
Please study all photographs carefully, as they form an important part of the description and show the glass, mount, missing focus grip and general cosmetic condition.