Pekka Buttler, 11/2022
The table below summarizes the lens’ key specifications (measurements based on pictured sample):
|Subfamily (if applicable)
|Filter ring diameter
|Lens element count
|Lens group count
|Aperture blades (S/R/C)5
|Minimum focusing distance
|Has manual aperture ring
|Has Manual focus ring
• The name Orestor identifies the lens as one of MOG’s later series (all MOG lenses post-1963 are named Orest-something).
• This 100 mm Orestor was the smaller sibling to the 135 mm f/2.8 Orestor [data sheet], that was similarly a Sonnar-type design.
• The introduction of the 100 mm Orestor marked the end of Meyer-Optik’s 100 mm f/2.8 Trioplan [data sheet].
• This Orestor was replaced in 1970 by the identical-specs Pentacon 100 mm f/2.8 (auto/electric), which however did not remain in production for long.
• For further notes on Meyer-Optik Görlitz and especially their naming logic, see the JAPB article on MOGnames (the company’s later history is summarised below).
History of Meyer-Optik Görlitz
The original Meyer-Optik Görlitz (not the modern company that has taken the classic company’s name) was founded in the town of Görlitz (modern-day Germany) by Hugo Meyer in 1896, and remained in existence until the state-directed merger into VEB Pentacon 1970. Due to its vicinity with the German camera and optics industries in Saxony (Dresden, etc.), Meyer-Optik was from an early stage heavily involved with manufacturing lenses for all kinds of cameras, but the company’s real golden age started with the advent of interchangeable lens cameras, where Meyer-Optik was uniquely placed to offer a cost-effective alternative to premium brands such as Carl Zeiss Jena.
Meyer-Optik was pronouncedly a camera lens manufacturer and never had serious ambitions for pursuing horizontal integration (diversifying into cameras and other photo gear). Instead, MOG pursued a vigorous strategy of seeking economies of scale, combined with never putting too many eggs in any basket – typically Meyer-Optik would choose which designs to put into production based on being able to cover as many platforms/mounts with one basic design. As a result, many early MOG designs were made available for a wide range of camera platforms. Later, as the number of alternative platforms diminished, that strategy had to go in favour of a strong focus on M42 and (to a somewhat lesser extent) Exakta. Even so, throughout the 60s, MOG vigorously pursued innovative designs and could by the end of the decade proudly offer a wide range of high-quality, cost effective designs.
When the lens maker Meyer-Optik was then merged with the camera maker Pentacon, it became obvious that the role the company (and its product portfolio) was intended to play was to aid Pentacon in its designs of gaining a significant global market share in the price-conscious consumer segment (and help bring hard currency to the G.D.R). Instead of focusing on continued optical innovation, the new overlords were more keen on redesigning lenses for greater economy and easier manufacture. As a result, the pace of optical innovation at MOG/Pentacon fell drastically, and very few new designs or significant redesigns were to be forthcoming in the next two decades.
However, the Meyer-Optik Oreston comes from what would later be known as the golden decade of Meyer-Optik. While the names Meyer-Optik and Oreston were soon to disappear from view, the design work done at Meyer-Optik would turn out to have an impactful legacy.
The 100 mm Orestor was introduced in two versions: a manual aperture (with click stops) version, and a version with automatic aperture, with stop-down button (pictured above). For Exakta only the manual aperture version was offered, whereas with an M42 mount there were three alternatives: manual aperture, M42 auto (m42 with stop-down pin) and M42 electric (three electric contacts for communicating aperture setting and stop-down pin).
All versions were initially (cosmetically) fully fledged Zebra lenses, but (as with all Meyer lenses in the late 60s) the number of zebra-ish elements declined as the 60s progressed.
Going forward from Meyer-Optik to Pentacon, the auto-version of the 100 mm Orestor would receive a new cosmetic, ‘Pentacon-esque’ look (the manual aperture version was scrapped).
n.B! The following applies this lens in either Exakta or M42 mount.
This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need an Exakta or M42-mount film body. Luckily there are a lot of those (especially in M42 mount) available.
Thanks to being a fully manual lens (manual aperture, manual focus), the lens can be adapted to all mirrorless cameras using a suitable adapter. Moreover, both Exakta and M42 lenses are so uncomplicated that a simple ‘dumb adapter’ will do the job perfectly. Moreover, due to the popularity of both mounts, special adapters (helicoid adapters, tilt/shift adapters) are readily available. Alternatively, one can choose to daisy-chain adapters (e.g. M42->Canon EF; Canon EF –> mirrorless) which also opens up a wide range of speed boosters .
Using m42 and Exakta lenses on dSLRs can also be an easy option, depending on which dSLR.
• Canon EF has the shortest flange focal distance among full-frame dSLR’s and Canon’s wide range of dSLRs are able to mount both M42 and Exakta lenses perfectly using a simple adapter ring.
• Minolta / Sony A dSLRs are likewise able to mount M42 lenses using a simple adapter ring, but for Exakta lenses, the difference in flange focal distances is not enough to enable reaching infinity focus without an adapter that uses corrective optics.
• Pentax K dSLRs are likewise able to use M42 lenses using a simple adapter ring, but for Exakta lenses an adapter that uses corrective optics would be needed to allow infinity focus.
• Nikon F dSLRs have a long flange focal distance, meaning that mounting either M42 or Exakta lenses needs an adapter that uses corrective optics to allow anything close to infinity focus.
1 Focal length is (unless stated otherwise) given in absolute terms, and not in Full-frame equivalent. For an understanding of whether the lens is wide/tele, see ‘Angle-of-view’.
2 Picture angle is given in degrees (based on manufacturers’ specs) 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.
4 Diameter excludes protrusions such as rabbit ears or stop-down levers.
5 S=straight; R=rounded; C=(almost)circular at all apertures.