Pekka Buttler, 03/2024
Specifications
The table below summarizes the lens’ key specifications (measurements based on pictured, last version of the lens):
| Brand: | Tokyo Kogaku (Topcon) | Lens name | RE. Auto-Topcor 1:2.8 f=100mm |
| Focal length(s)1 | 100 mm | Angle-of-view2 | 24,4 ° |
| Maximum Aperture | f/2.8 | In Production | 1965–1977 |
| Lens mount (this lens) | Topcon/Exakta | Generation | RE. Auto-TOPCOR3 |
| Length4 | 54,1 mm | Diameter5 | 63,1 mm |
| Filter ring diameter | 49 mm | Weight | 277 grams |
| Lens element count | 5 | Lens group count | 3 |
| Aperture blades (S/R/C)6 | 6 S | Focus throw | 270 ° |
| Minimum focusing distance | 1,2 m | Maximum magnification | 1:9,9 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
Further notes:
• In an era when most lenses were uniformly black (and when even silver rings were going out of fashion), Topcon went in the opposite direction in the styling of their Topcon RE. Auto-TOPCOR series of lenses. These lenses were initially matte silver, with black rubber grips giving a contrast. However, after the 1971 introduction of the Super D, Topcon also started offering its lenses in black.
• Alike most Topcon RE. Auto-TOPCOR lenses of its era, this lens sports a chromed bayonet for attaching a lens hood as well as filter threads.
• The filter threads do not rotate on focusing.
• The aperture ring offers half-stop clicks throughout the range.
Versions and variations
This 100 mm f/2.8 Topcon lens was the dedicated portrait lens for the Topcon RE system until the 1970 introduction of the Topcon 85 mm f/1.8. The later lens was however always more expensive, leading to this lens remaining popular until the demise of the system. After the 1977 downgrading of the Topcon RE system, this lens was not replaced with another design.
The earliest samples of the 100 mm f/2.8 reported their focal length in centimetres. It is unclear when exactly this changed.
During the 12 years this lens remained in production it was manufactured in silver (from 1965) and in black from (1972). I have found nothing to indicate that there would exist any optically significant variations.
History of Topcon
Unless you know your camera lore, you might not know that Topcon was once – between 1957 and 1976 – one of the foremost camera companies in the world.
You can read more details in the Topcon company profile.
Adapting
When intending to adapt Topcon/Exakta lenses keep in mind that most Topcon/Exakta lenses have control pins in the lens flange that vanilla Exakta lenses do not have. Hence, there is a theoretical possibility to that some old-time Exakta adapters have been manufactured that do not accommodate these pins. When procuring an adapter, make sure that it explicitly is compatible with Topcon lenses, or visually inspect the adapter regarding whether it makes room for the Topcon control pins.
With that caveat, the following applies to all Topcon/Exakta mount lenses.
This lens cannot be used natively on any current SLR or dSLRs. To use it in its native environment, you will need a Topcon RE Super film body or one of the subsequent Topcon cameras with the Topcon Exakta mount. While these were never produced in immense numbers, they seem to have stood the test of time reasonably well, and can still be found in perfectly serviceable condition.
Thanks to being a fully manual lens (manual aperture, manual focus), the lens can be adapted to all mirrorless cameras using a suitable ‘dumb adapter’. Moreover, due to the popularity of the Exakta mount, special adapters (helicoid adapters, tilt/shift adapters) are readily available.
Using Exakta mount lenses on dSLRs can also be an easy option, depending on the marque of 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 Topcon/Exakta lenses perfectly using a simple adapter ring.
• Minolta / Sony A dSLRs, Pentax K and Nikon F mount dSLRs do not have a short enough flange focal distance to enable reaching infinity focus without an adapter that uses corrective optics.
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 ↩︎ - See more about Topcon lens generations in Topcon Company profile. ↩︎
- 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. ↩︎