Lenses with interchangeable mounts were developed primarily to solve the inventory management problems of the photo equipment retailers of the late 50s.
After Asahi launched their “Pentax” single lens reflex camera with interchangeable lenses in 1957, German and Japanese camera makers jumped on the band wagon and started releasing their own lines of SLR bodies and lenses.
They formed two camps – vendors like Mamiya, Petri, Ricoh, Fujica, Chinon, Yashica followed the example of Asahi and Praktica and adopted the 42mm “universal” screw mount – with the promise of inter compatibility between brands. On the other hand, Canon, Exacta, Leica, Minolta, Miranda, Nikon, Topcon and a few others brands each decided to develop their own proprietary bayonet mount.
Those were the early days of the SLR, and the pace of progress was fast. Manufacturers had to revise their lens mounts every few years, in order to support new features such as automatic aperture preselection, full aperture metering and various exposure automatism implementations.
Imagine the nightmare for a retailer – having to stock expensive lenses for each variant of each of those mounts.
There was an opportunity for an inventive manufacturer to produce a line of universal lenses designed to be fitted with the lens mount adapter needed by the customer at the last minute, in the store, when he was ready to buy. The retailer could serve almost any customer need with only one copy of each universal lens, and one lens mount adapter per camera brand.
Of course, the photographer buying one of those “universal” lenses could also play Lego himself – and use his lens with camera bodies of different manufacturers (if he happened to be transitioning from one camera brand to another one, for instance).
Tamron is widely credited for being the first to market such a solution in the late 50s (with their T mount lenses), but Soligor and Vivitar also adopted the T mount and developed their own lines of lenses.
In order to keep up with the increasing complexity of the lens mounts, they regularly launched new lines of adapters and matching lenses : Tamron with the Adaptamatic (in 1969), Adaptall (in 1973) and the Adaptall 2 (in 1979), Soligor and Vivitar with the T4 and the TX system.
The progressive generalization of automatic cameras with multiple auto-exposure modes made the lens mounts much more complex and delicate. The growing use of electronics and the auto-focus revolution of the mid 80s presented technical challenges of increasing difficulty that could not be overcome at a reasonable cost. And the concentration of the auto-focus SLR market into a handful of players (Canon, Minolta, Nikon and Pentax) made inventory management easier for the retailers. As a result, the interchangeable lens mount system was gradually abandoned by its manufacturers in the 90s.
Today, does it make sense for a photographer using manual focus SLRs to buy interchangeable mount lenses ?
- Canon and Nikon users should not be too concerned: their cameras were often used by professional photographers who had to invest in a large set of good lenses to stay competitive. Today, Canon FD and Nikon F lenses are abundant (and therefore comparatively cheap) on the second hand market, in any focal length.
- but photographers using cameras of other manufacturers are not that lucky: the original buyers of those cameras were primarily amateurs, and the 50mm standard and the 135mm tele-objective seem to be the only lenses that they bought 40 years ago. They are the only ones easy to find on the second hand market today. When an OEM wide angle or a short tele-objective lens shows up on eBay, its price rapidly reaches insane levels.
- For those photographers using cameras from second or third tier manufacturers, Tamron or Vivitar lenses are an interesting alternative: the interchangeable lens mounts are still easy to find and cheap (some of them New Old Stock), and the lenses are more abundant and not as expensive as most OEM lenses.
- Zoom lenses from the 70s and early eighties generally have a bad reputation, and those with interchangeable lens mounts are not better than the rest. But some prime lenses from Tamron are very well regarded, and constitute interesting purchases on their own merit (the Tamron 90mm f/2.5 Macro lens in particular)
- Users of digital mirrorless cameras have an extra option – some vendors propose direct Adaptall to mirrorless adapters (for the most common mirrorless mounts: Sony, Fujifilm and Micro 4/3). Since mirrorless cameras don’t need to control the aperture of the lens to operate in some of their automatic modes, the adapter does not need to provide any linkage between the camera’s mount and the lens. It can be extremely simple – and cheap.
Sources:
https://en.wikipedia.org/wiki/T-mount
http://www.tremyfoel.co.uk/photography/Adaptall/TamronAdaptallInfo.html
http://mattsclassiccameras.com/lenses/adaptall-2-system/
and specifically for the Fujica X bayonet (manual focus SLR bodies: ST-X and AX-1, AX-3, AX-5): tamron adaptall 2
https://www.photo.net/discuss/threads/t-mounts-t-t-2-t-4-tx.245015/
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