Minolta MC Rokkor Lenses

When Minolta introduced the SR-T101 in 1966 with built in metering through the lens (TTL) as an logical succession to the SR-7 which also had a built in meter, this might be seen today as a small step in the development of the SRL camera. But when the SR-7 had a meter that looked through an eye of the side of the camera, coincidence metering as it's called, the SR-T101 not only measured the light coming through the lens, the real evolution was that the metering took place with the aperture fully open.
Using other cameras with TTL metering, you would first have to stop down the lens to take a metering of the scene, then opening up the lens to focus accurately, otherwise the viewfinder is both dark and difficult to gauge the correct focus.
To enable this feature the lens must signal the set aperture to the camera to be able to compensate the light coming through the lens during fully open aperture, to the moment of exposure when the aperture closes down to working aperture. This is the MC or meter coupled lenses of the MC Rokkor line.

Minolta SR-T101 with MC Rokkor lenses 100mm/3.5, 58mm/1.4, 35mm/2.8 and 135mm/2.8

Most of the lenses of the MC Rokkor line was transformed from previous Auto Rokkor lenses, and the optical design was carried over with the addition of the MC tab to signal the aperture set on the lens.
In appearance the MC Rokkor line looked much like the previous third generation of the Auto Rokkor lenses, the most obvious difference was the chromed aperture ring of the MC Rokkor.

Early lenses from the MC Rokkor period with a Rokkor 100mm/4.0 to far right.

During the production of the MC Rokkor line some of the lenses was modified with new optical design and when that affected the size of the lens, it was also changed in appearance.
The most notable example was the MC Rokkor-SG 28mm 1:3.5 that was almost unchanged in appearance between Auto Rokkor and in its first MC Rokkor guise, and subsequently was remade in a new design, although still a -SG (7 glasses in 7 groups) design, the lens was much smaller thanks to a radical redesign made possible by new types of optical glass.

Standing side by side, the Auto W.Rokkor-SG 28mm/3.5 (right) and the MC W.Rokkor-SG 28mm/3.5 are almost identical.

The old MC W.Rokkor-SG 28mm/3.5 (left) is much larger when standing next to the new modified MC W.Rokkor-SG 28mm/3.5.

New lenses was added to the MC Rokkor line like the first Fisheye lens, the Rokkor 18mm 1:9.5 fullframe Fisheye and MC Tele Rokkor-QD 135mm 1:3.5 lens which suppleanted the older Rokkor-TC 135mm 1:4.0 tele lens for those looking for a more economical choice.

The early MC Rokkor 135mm lenses flanking the venerable 135mm/4.0 Rokkor.

Some time before 1970 the MC Rokkor line got a new slightly altered cosmetical appearance. The focusing grip of the second generation of MC had knuckled shaped knurles and was much wider, the first MC generation had longer focusing grip unless the barrel of the lens was short.

MC Rokkor 28mm/3.5 lenses of first and second generation showing the difference of focusing grip with the caractaristic knurled grip against the older appearance.

It is worth mentioning that Minolta that had been a forerunner in developing anti reflective coating of lens surfaces continually developed and enhanced the anti reflective properties of their coating of lenses. That technology made great strides too, but did not change dramatically with the introduction of each generation of lenses.

Second generation of MC Rokkor lenses with typical knuckle shaped focusing grip.

The MC Rokkor line was a high quality line of lenses from Minolta with high finish and technical standards. The MC Rokkor line placed Minolta at a technical refinement ahead of its main competition. It cannot be stretched enough that this level of technical development took years for Minolta's competitors to catch up to the same level of advancement.
In 1972 it was time for Minolta to launch the third and last major cosmetic change of the MC Rokkor lenses, the rubber clad MC Rokkor, often referred to as the MC Rokkor-X lenses.

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