Data sheet: A.Schacht Ulm Travelon 50 mm f/1.8 (M42)

Pekka Buttler, 01/2025

Specifications

The table below summarises the lens’ key specifications (measurements based on pictured sample):

Brand:	A.Schacht Ulm	Lens name	Praktica-S-Travelon 1:1,8/50 R
Focal length(s)1	50 mm	Angle-of-view2	47°
Maximum Aperture	f/1.8	In Production	1959–≈1970
Lens mount (this lens)	M42	Other lens mounts	Exakta
Length3	37,6 mm	Diameter4	59,1 mm
Filter ring diameter	49 mm	Weight	194 grams
Lens element count	6	Lens group count	4
Aperture blades (S/R/C)5	6 S	Focus throw	≈315 °
Minimum focusing distance	50 cm (measured)	Maximum magnification	1:8,0 (measured)
Has manual aperture ring	YES	Has Manual focus ring	YES
Aperture mechanism type	Auto/Manual6	Aperture click stops7	1.8-2•2.8•4•5.6•8•11•16•22

Further notes:
• This is a relatively late A.Schacht lens and also the fastest standard lens ever produced by A.Schacht.
• This M42 auto aperture lens has a M/A aperture mechanism switch and a pin in the mount used to facilitate aperture automation.
• This lens – alike most later-era A.Schacht lenses have a very Germanly over-engineered depth-of-field system, where the depth-of-field is illustrated by the light area between the red zones (between aperture and focus rings). That indicator is coupled to the aperture ring, hence the depth-of-field widens as the aperture is closed down – Natürlich. ⁸.
• At infinity the rearmost lens element intrudes relatively far back, and may collide with the mirror in some cameras.

Versions

There are two fundamentally different versions of the 50 mm f/1.8 Travelon: one for the Exakta mount and another for the M42 mount(s).

The Exakta mount version is an auto aperture variant with a ‘pod’ for aperture automation and pass-through (see the JAPB article on the Exakta mount).

Of the M42 mount versions there seem to be three different sub-variants of this lens:
• The ‘plain’ variant, named: “A.Schacht Ulm S-Travelon 1/1,8/50 R”
• The ‘Praktica’ variant, named “A.Schacht Ulm Praktica-S-Travelon 1/1,8/50 R” (this lens)
• The ‘Edixa’ variant, named “A.Schacht Ulm Edixa-S-Travelon A 1/1,8/50”

The reason for the Edixa and Praktica variants is that Edixa – in true West German fashion – used their own variant of the M42 mount (see discussion here) and that the ‘Praktica’ and ‘Edixa’ named variants existed to inform consumers of which camera the lens was intended for. To the best of my knowledge, the ‘plain’ version is identical to the ‘Praktica’ version.

For the sake of adapting the three M42 variants all work. With the ‘Edixa’ variant it is possible¹⁰ that one must use an adapter that does not interact with the stop-down pin to retain infinity focus.

The history of A.Schacht

The optics company A. Schacht was active from 1948 to 1967. It produced interchangeable lenses for several mounts including Exakta, Leica thread mount, M42 and Praktina. See more details in the A.Schacht company profile.

Adapting (vanilla M42 version)

If you want to natively mount this lens you need to find a functioning m42 mount film camera. Luckily that should be relatively easy as m42 bodies were produced in their millions and most of them lack features that are especially likely to have deteriorated to the point of making the entire camera inoperable.

Adapting this lens to a mirrorless, full-frame digital camera is a breeze thanks to the lens having full manual controls (aperture ring, focus ring). You simply need a dumb adapter from m42 to your mirrorless system (And set the lens in manual mode to be sure the aperture works as you intend).

Due to the medium flange focal distance used by the m42 mount (45,46 mm), whether you can adapt this lens to dSLR/SLR mounts depends on which dSLR mount: Canon EF, Four Thirds, Minolta/Sony A and Pentax K can mount m42 lenses using a simple adapter ring. Nikon F on the other hand is not as problem-free, and – to retain anything near infinity focus – the adapter will necessitate corrective optics. In all cases, your camera will work only in stop-down metering.

Footnotes

1. Focal length is (unless stated otherwise) given in absolute terms (not in Full-frame equivalent), and according to the manufacturer’s naming practice (which does not always reflect the lens’ actual field of view). For an understanding of whether the lens is wide/tele, see ‘Angle-of-view’. ↩︎
2. Picture angle is given in degrees and concerns the diagonal picture angle. Rule of thumb:
   > 90 ° ==> Ultra-wide-angle
   70–90 ° ==> Wide-angle
   50–70 ° ==> Moderate wide-angle
   40–50 ° ==> ‘Standard’ or ‘normal’ lens
   20–40 ° ==> Short tele lens
   10-20 ° ==> Tele lens
   5-10 ° ==> Long tele lens
   < 5 ° ==> Ultra-tele lens ↩︎
3. Length is given from the mount flange to the front of lens at infinity. Measured unless stated otherwise. ↩︎
4. Diameter excludes protrusions such as rabbit ears or stop-down levers. Measured unless stated otherwise. ↩︎
5. S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎
6. Alike many M42 lenses, this A.Schacht lens has a switch to choose between Manual and Auto aperture. ↩︎
7. Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎
8. Many lenses for the DKL-system also offer a similar arrangement. See e.g. this DKL lens ↩︎
9. I have found online accounts to this effect but cannot verify them. ↩︎