Pekka Buttler, 07/2025
This lens has also been on a JAPB walk-around. If you’re interested in imagery and impressions, please refer to that walk-around.
Specifications
The table below summarizes the lens’ key specifications (measurements based on pictured sample):
| Brand: | Pentacon | Lens name | auto 2.8/100 |
| Focal length(s) 1 | 100 mm | Angle-of-view 2 | 24 ° |
| Maximum Aperture | f/2.8 | In Production | 1970–1975 |
| Lens mount (this lens) | M42 | Other lens mounts | Exakta (RTL variant) |
| Length 3 | 57,7 mm | Diameter 4 | 63,4 mm |
| Filter ring diameter | 49 mm | Weight | 282 grams |
| Lens element count | 5 | Lens group count | 4 |
| Aperture blades (S/R/C) 5 | 6 S | Focus throw | 330 ° |
| Minimum focusing distance (measured) | 105 cms | Maximum magnification (measured) | 1:8,4 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
| Aperture mechanism type | Automatic | Aperture click stops 6 | 2.8•4•5.6•8•11•16•22 |
Further notes:
• This lens is optically the same lens as the Meyer-Optik Görlitz Orestor 100/2.8.
• The MOG Orestor 100/2.8 was introduced in the late 1960s and after the state-directed merger of Meyer-Optik Görlitz into VEB Pentacon, the lens continued to be sold as the Pentacon 100/2.8
• There were four version of the Pentacon 100 mm f/2.8. See more under ‘versions‘
History of Pentacon
There is little doubt that Germany was once world leader in the designing of cameras, lenses, and pretty much anything else photography related. Moreover, within Germany (pre-WWII Germany, to be precise), there was a region along the middle of the river Elbe and its tributary the Saale that would have earned the moniker Silica Valley. Just like the modern Silicon Valley, this area was a powerhouse of innovation within the still nascent photo-optic industry, housing both a plethora of camera makers, lens makers, and other, supporting industries. Optics was a booming industry, and even wars did little to change the industry’s growth trajectory.
But after the Second World War and the ensuing uneasy peace between the Western Allies and the Soviet Union, Silica Valley – residing in the modern German states of Thuringia and Saxony – ended up in the Soviet Zone of control, that – as tensions between erstwhile allies grew – developed into the ‘German Democratic Republic’ or East Germany – a Soviet satellite state directly juxtaposed to the ‘German Federal Republic’ or West Germany.
The Soviet-inspired East German system had no love lost for private enterprise (which was seen as tantamount to a rentier-class exploiting the proletariat), nor for companies competing for customers (which was seen as a woefully inefficient method for allocating scarce resources). Hence, most enterprises were quickly nationalised, and competing companies were continuously being forcibly merged with their erstwhile competitors. One result of this policy was the 1964 founding of VEB Pentacon Dresden (VEB = Volkseigener Betrieb ≈ Peoples’ own enterprise).
VEB Pentacon was founded through the merger of
• VEB Kinowerke Dresden (formerly VEB Zeiss Ikon),
• VEB Kamera-Werke Niedersedlitz (previously Kamera-Werkstätten Charles A. Noble),
• VEB Welta-Kamera-Werk Freital (incl. VEB Reflekta-Kamerawerk Tharandt),
• VEB Altissa-Camera-Werk Dresden,
• VEB Aspecta Dresden.
As a result, the central planners in East Berlin had merged the majority (Ihagee, makers of the Exakta were left alone, for now) of East German camera makers into one giant company. The resulting Pentacon (the name is a portmanteau of ‘Pentaprism’ and ‘Contax’) however focused solely on manufacturing cameras, and instead sourced their lenses from East German lens makers (mainly Carl Zeiss Jena and Meyer-Optik).
But with the success – both domestic and international – of Pentacon cameras, especially the Praktica line of SLRs, Berlin seems to have considered tighter co-ordination to have been the the next order of business. Hence, in 1968 VEB Feinoptishes Werk Görlitz (which had managed to keep branding their lenses ‘Meyer-Optik’ even though such singling out of one person (Hugo Meyer) was against the Soviet creed) and Ihagee were merged into Pentacon, making the resulting Pentacon a fully vertically integrated colossus (or, in soviet parlance, a combine.).
During the next two years, lenses previously having been branded Meyer-Optik Görlitz, started leaving their factory carrying the brand ‘Pentacon’ 7. Meyer-Optik had made some shrewd operational and design decisions, and in the post-war environment, characterised strongly by the proliferation of various SLR’s and other cameras (read: strong demand for lenses), MOG was having a field-day. Especially in the 1960s – just prior to the merger – Meyer-Optik was very prolific in coming up with new, cutting edge designs, so when Pentacon ‘took over’ Meyer’s lens catalogue, Pentacon was able to offer a broad range of cameras as well as lenses characterised by a very good bang/buck ratio.
While the merger worked wonders for Pentacon, the same can not be said for Pentacon lens designing. After having made immense progress in the 60s, Meyer/Pentacon lens design stagnated throughout the 70s and 80s. That is not to say that the lens lineup stayed unchanged, but that changes were either focused on minor recomputations of existing designs, economically driven simplification of lens mechanics, increased use of plastics, gradual adoption of better coatings and adoption of the Praktica B mount. It is sad to say that in the 20+ years after the Pentacon-Meyer merger, only one new lenses was introduced and only two lenses were given a major design tweak.
While I don’t want to give the impression that Pentacon lenses are generally sub-par (they were not, especially not when considering price), I am immensely saddened by the lost potential, especially considering the strides Japanese manufacturers were taking during that time. From Meyer having been at the forefront of innovation in the mid 1960s, Pentacon in the mid 1980s was increasingly the choice of only budget-conscious or ideologically inclined consumers.
Versions
The preceding MOG Orestor 100/2.8 was introduced in two versions: a preset aperture (with click stops) version (M42 or Exakta), and a version with automatic aperture, with stop-down button. This automatic aperture variant could be either of the M42 auto (m42 with stop-down pin) and M42 electric (three electric contacts for communicating aperture setting and stop-down pin).
After Pentacon took over the MOG lens catalogue the M42 versions remained in the lineup, but the preset Exakta was discontinued. Instead, the Pentacon 100/2.8 exists with a mount designed to be used with the Exakta RTL 1000.
In short: the following (mechanically distinct) versions exist (which have identical optics):
• Pentacon 100/2.8 M42 automatic
• Pentacon 100/2.8 M42 electric
• Pentacon 100/2.8 Exakta RTL 1000
Finally, there might be some samples of a Pentacon 100/2.8 M42 Preset (these would have been remaining stocks of Orestor 100/2.8 preset parts being sold off in the midst of the rebadging).
There are at least two cosmetic variants of the Pentacon 100/2.8:
• One version with broad zebra stripes on the aperture ring and with the background for aperture values in silver (but otherwise black)
• One all-black version (pictured sample)
Adapting
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.
Footnotes
- 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’. ↩︎
- 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 ↩︎ - Length is given from the mount flange to the front of lens at infinity. ↩︎
- Diameter excludes protrusions such as rabbit ears or stop-down levers. ↩︎
- S=straight; R=rounded; C=(almost)circular at all apertures. ↩︎
- Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎
- • Pentacon 29/2.8 = Meyer-Optik 29/2.8 Orestegon
• Pentacon 30/3.5 = Meyer-Optik 30/3.5 Lydith
• Pentacon 50/1.8 = Meyer-Optik 50/1.8 Oreston
• Pentacon 100/2.8 = Meyer-Optik 100/2.8 Orestor
• Pentacon 135/2.8 = Meyer-Optik 135/2.8 Orestor
• Pentacon 200/4 (preset) = Meyer-Optik 200/4 Orestegor
• Pentacon 300/4 = Meyer-Optik 300/4 Orestegor
• Pentacon 500/5.6 = Meyer-Optik 500/5.6 Orestegor ↩︎