Pekka Buttler, 09/2026
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 TOPCOR 1:1.7 f=55mm |
| Focal length(s)1 | 55 mm | Angle-of-view2 | 43 ° |
| Maximum Aperture | f/1.8 | In Production | 1977–1978 |
| Lens mount (this lens) | Topcon/Exakta | Generation | RE TOPCOR3 |
| Length4 | 37,4 mm | Diameter5 | 62,5 mm |
| Filter ring diameter | 52 mm | Weight | 207 grams |
| Lens element count | 6 | Lens group count | 4 |
| Aperture blades (S/R/C)6 | 6 S | Focus throw | 170 ° |
| Minimum focusing distance (measured) | 59 cms | Maximum magnification (measured) | 1:9,0 |
| Has manual aperture ring | YES | Has Manual focus ring | YES |
| Aperture mechanism type | Automatic | Aperture click stops 7 | 1.7••2.8•4•5.6•8•11•16 |
Further notes:
• This is a late-era Topcon lens. It hails from an era when Topcon had already given up the fight and was merely trying to profit on its past fame.
• This lens (along with one zoom and a moderate range of primes) was launched alongside the Topcon RE 200 camera in 1977.
• This 55 mm f/1.7 (as well as the RE 200 camera and the other lenses in this series) are often stated to be manufactured by Cima Kogaku. While this is technically true, this is often stated to imply that Topcon was so ‘cheap’ that it even subcontracted its swansong system to some practically unknown Japanese OEM whereas Cima Kogaku seems to have been a Topcon spinoff.
• Being a Topcon RE-series lens it is fully compatible with every Topcon professional/prosumer camera from the 1963 RE Super to the 1978 RE300 (RE Super, RE-2, Super D, Super DM, RE200, RE300)
Versions and variations
This Topcon 55 mm f/1.7 RE TOPCOR lens is the nifty fifty for the late-era Topcon RE system and was often bundled with the Topcon RE200 and RE300 cameras. It is a fairly standard nifty fifty for its era, with the exception of its focal length (at 55 mm) being a bit longer than the 50 mm that had established itself as the industry standard by this time.
The lens’ optical design is not a remake of an earlier Topcon design, but seems to be slightly related to the Topcon HI Topcor 55 mm f/1.8 for the Topcon UV system [data sheet].
The lens was available in two variants that seem to be optically identical:
• The Topcon RE TOPCOR 55 mm f/1.7 for the Topcon/Exakta mount (this lens)
• The Topcon AM TOPCOR 55 mm f/1.7 for the Pentax K mount (sold with the Topcon RM300)
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. ↩︎
- Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎