A bit of history

1964: Leica is diversifying into SLRs

Leica, primarily known for its rangefinder cameras, also produced SLRs from 1964 with the Leicaflex until 2002 with the Leica R9.

While the lenses of these SLRs don’t have the same reputation as the rangefinder models, they are nonetheless excellent.

Personally, I prefer the « R » SLR to the « M » rangefinder for its close-up photography capabilities (very practical for photographing flowers, for example).

The lenses are not interchangeable between the brands, as the two devices have their own mounts.

In the 1960s and 70s, Leica faced difficulties: rangefinders were selling less than SLRs.

Leica’s first SLR cameras: the Leicaflex series. A mixed success.

An attempt was made in 1964 with the Leicaflex, but the camera failed to gain traction amidst the already well-established Nikon F and Spotmatic cameras.

In the early 1970s, Leica struggled to make the latest iteration of the Leicaflex, the SL2, profitable.

An alliance with Minolta to move forward

To overcome these difficulties, the decision was made to partner with Minolta in order to reduce development costs.

End of the Leicaflex mechanical era, start of the « R » electronical era

The Leicaflex where beautiful mechanical cameras (it only require a battery for the posemeter). With the R3, Leica evolves and use a more precise electronical shutter and adds an automatic aperture priority mode.

The « sister cameras »: Leica R3 and Minolta XE-1 (alias XE or XE-7)

In 1976, this partnership resulted into two « sister cameras »: the Leica R3 Electronic and Minolta XE-1 (also known as XE or XE-7).

A shape regression for the R3 comparing to the Leicaflex

As a consequence of these changes and compromises of the collaboration, the R3 was less refined and consistent regarding the shape and handling than the Leicaflex cameras.

The design of the XE-1 is more coherent than that the R3 one.

The shared parts

The shutter developed by Leitz and Copal, which allowed for a reduction in the camera’s size, is shared.

The same is true for the film advance mechanism, made of plastic, and the chassis, which I imagine was designed by Minolta (I haven’t found any information on this, but I presume so given the materials used and the chassis’s shape, which contrasts sharply with Leicaflex cameras).

The cameras do not share any other parts.

Many parts specific to each cameras

Leica being synonymous with high-end, the R3 is technologically more advanced than the XE-1.

I can’t go into more detail because the only parts of a camera I actually use are the shutter and the film advance mechanism.

In short, the R3 offers better light metering and greater viewing comfort than the XE-1.

A successful collaboration

Leica achieved sufficient success with the R3 to move forward. The collaboration with Minolta continued with the R4 and Minolta XD-7.

Leica resumed developing alone its SLR cameras in the mid-1980s with the leica R5.

Sources :
http://www.summilux.net/materiel/Leicaflex
http://www.summilux.net/materiel/Leica-R3