Data sheet: Tamron 28-50 mm f/3.5–4.5 CF MACRO BBAR MC (adaptall-2)

Pekka Buttler, 11/2026

Specifications

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

Brand:	Tamron	Lens name	1:3.5-4.5 28-50mm CF MACRO BBAR MC
Focal length(s) 1	28-50 mm	Angle-of-view 2	75°–47°
Maximum Aperture	f/3.5–4.5	In Production	1980–82
Lens mounts (native)	Tamron Adaptall	Other lens mounts	See article on Adaptall
Length 3	51,0 mm (with Nikon F adapter)	Diameter 4	64,7 mm
Filter ring diameter	52 mm	Weight	258 grams (without adapter) 315 grams (with Nikon F adapter)
Lens element count	9	Lens group count	9
Aperture blades (S/R/C) 5	5 S	Focus throw	100 ° (at 28 mm) 300 ° (at 50 mm)
Minimum focusing distance (measured)	63 cms @ 28mm 26 cms @50 mm	Maximum magnification (measured)	1: 20,7 @28mm 1:4,3 @50 mm
Has manual aperture ring	YES	Has manual focus ring	YES
Aperture mechanism type	Automatic	Aperture click stops (on preset ring) 6	3.5-4•5.6•8•11•16-22

Further notes:
• This lens was designed to use the Tamron Adaptall2 intermediate mount
• Tamron has always had its own coding scheme for lens designs. This coding scheme is extremely useful to discern between two (or more) lenses that have the same mainline specifications (focal length and maximum aperture). According to the Tamron coding scheme, this lens is “Model 07A”.
• When Tamron introduced the Adaptall-2 variant of its intermediate mount, they also introduced a ‘premium’ line of more pro-oriented lenses under the ‘SP’ (Superior Performance) acronym.
• Also, from the very start of the Adaptall-2 line, Tamron introduced two wide zooms: one 24–48 mm lens in the SP line, and this 28–50 mm less ambitious design.
• For some reason this lens was discontinued after only two years and not directly replaced with another design.

• The lens uses Tamron’s CF MARCO operating logic (CF stands for ‘Continuous focusing’), meaning that as you rotate the focus ring to focus closer, this will also change the focal length setting to make sure that you can zoom as close as you want.
• Hence also the lens has a relatively modest MFD at the 28 mm (wide-angle) focal length setting, moving towards a more ambitious 26 cm MFD at the 50 mm (standard setting). (In practice the effective focal length at the MFD setting is close to 40 mm)

• The focus ring is narrow but luckily quite grippy. The zoom ring is very narrow but has small ‘wings’ – partially to improve grip, partially to aid in finding the zoom ring without needing to stop looking through it.
• The aperture ring is narrow, but somewhat manageable.
• The lens’ filter threads rotate when focusing.

Versions and variants

Likely in part due to the short production run, there seems to be only one variant of this Tamron lens.

Adapting

Given that this lens uses an intermediate mount, there are several ways to go, depending on what your intention is

If you intend to adapt your Tamron Adaptall lens to a dSLR…

There are original Tamron Adaptall adapters to both Pentax K and Nikon F (Ai) available. These adapters allow you to use the tamron Adaptall lens as if it was a native (manual focus) lens (including aperture and aperture priority exposure automation). There are also modern adapters available from several adapter manufacturers, but – in general – these adapters are dumb adapters and do not allow aperture control.

If your dSLR is a Canon EF or Sony/Minolta A and Four thirds camera, you can get an aftermarket dumb adapter, but will have to manually control aperture.

To film SLRs?
You’re in luck, because there used to be Adaptall/Adaptall-2 adapters made for pretty much every mainstream SLR system available before the mid-70s, (including at least⁷: Canon FD*, Contax/Yashica*, Fujica X†, Konica AR*, M42 (several variants⁸), Mamiya Z°, Minolta SR*, Miranda°, Nikon F° (Pre-Ai and Ai), Olympus OM*, Pentax K (K° and A† versions), Praktica B†, Rollei QBM° and Topcon RE° (Exakta). What you need to do is head to your favourite online classifieds platform and procure an adapter (adapters for dSLR mounts are still available new).

Notes:
* Available both as Adaptall 1 and 2 (with different features)
° Available only as Adaptall 1
† Available only as Adaptall 2

To Mirrorless
If you already have a number of adapters from the typical SLR mounts to your mirrorless camera (e.g. Canon FD / M42 / Nikon F / Olympus OM / Pentax K …) your best choice is to either:

• get an original Tamron adapter from Adaptall to whatever your most favoured SLR era lens mount is or
• get a modern Tamron adapter to mirrorless adapter from one of the contemporary adapter manufacturers (K&F Concept seems to offer dumb adapters for Adaptall to most mirrorless mounts)

Of these, the earlier option is likely to be cheaper and the later less finicky.

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. Numbers equal aperture values on aperture ring; • intermediate click; – no intermediate click. ↩︎
7. This list will only contain adapters that we at JAPB have witnessed.  ↩︎
8. There were both adaptall adapters to vanilla M42 mounts as well as some of the M42 variants (such as Fujica M42, Mamiya M42, Praktica electronic M42). For details, see the JAPB article on the m42 mount. ↩︎