Data sheet: Feinmess Dresden Bonotar 105 mm f/4.5 V

Pekka Buttler, 03/2023

Specifications

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

Brand:	FEINMESS DRESDEN	Lens name	Bonotar 4.5/105 V
Focal length(s) 1	105 mm	Angle-of-view 2	23°
Maximum Aperture	f/4.5	In Production	1956–1959
Lens mounts	Exakta, m42, Praktina	Subfamily (if applicable)	—
Length 3	84,9 mm	Diameter 4	53,8 mm
Filter ring diameter	40,5 mm	Weight	166 grams
Lens element count	3	Lens group count	3
Aperture blades (S/R/C) 5	10 S	Focus throw	240 °
Minimum focusing distance	1,7 m	Maximum magnification	1:14
Has manual aperture ring	YES	Has Manual focus ring	YES
Aperture mechanism type	Manual	Aperture click stops	None (clickless)

Further notes:
• Feinmess (or Feinmeß) Dresden ⁶ is not a big name in lens manufacture. In fact, this 105 mm ‘Bonotar’ is the only interchangeable lens to ever be produced by the company (the literal meaning of the name Feinmeß is ‘fine/precise measure(ment)’)
• This lens is a triplet construction, originally designed for use in medium format folding cameras. For a 6×9 format camera a 105 mm f/4.5 is pretty much par for the course (for the 1950s).
• As folding cameras were passing out of favour, the lens was repurposed to act as an interchangeable lens. When used on a 35 mm film camera it becomes a short tele (and a not very bright at that), but it does mean that the Bonotar gets one hefty sweet spot advantage.
• Even so, the Bonotar was never intended to compete with the finest the East German optics industry had to offer. Instead it was from the beginning intended as a cheap, light tele ⁷ for the occasional user. For the entire time that it was produced, it was the cheapest lens available in East Germany.
• While only some thousands of Bonotars were manufactured, there are nevertheless three outwardly distinct versions:
• Version 1A: Broad focus ring and aperture ring grip, bare aluminum (silver-coloured)
• Version 1B: As version 1A, but entirely black
• Version 2: Narrow focus ring grip (8 mm) and narrow aperture ring (silver-coloured) [pictured lens]
• Interestingly all Bonotars were coated (the red letter V) and while those coatings are no match for modern coatings, they seem to help, especially when the sun is just outside the field.
• All Bonotars (for all mounts) were manual aperture lenses. The aperture changes as you turn the aperture ring, the aperture scale is is not evenly spaced, and the aperture ring is click less.

Adapting

(The discussion below will focus on adapting M42 and Exakta variants. For a discussion on adapting Praktina mount variants, see JAPB’s article on the Praktina 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 (or Praktina) mount film body. Luckily there are a lot of those (especially in M42 mount) available. When doing so, keep in mind that the lens has a manual aperture mechanism and a relatively dim maximum aperture ⁸.

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 for those photographers that use smaller than full-frame sensors.

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

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 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. ↩︎
6. While Feinmeß Dresden was not big in interchangeable lens manufacturing , it was a key supplier to the Dresden photo/optical industry. Interestingly, Feinmeß Dresden exists to this day. See details here. ↩︎
7. I think this is a bit of a ‘curiosum’ lens, hence I condone a level of frivolity in this data sheet. Here it comes: at 166 grams per 105 mm of focal length, I suspect this lens has the lowest ratio of weight-to-focal-length (1,58 g/mm) of any serially manufactured Full-frame SLR lens ever! ↩︎
8. I find it somewhat ironic that while the Feinmess Bonotar might have been a ‘dog’ of a lens in its day (manual aperture instead of preset or auto; low maximum aperture leading to an unavoidably dim viewfinder image), most of these handicaps are entirely eliminated when the lens is adapted to a moder mirrorless camera. ↩︎