I just got a MC Rokkor-PF 1:1.7 55mm on a SRT 101 and a MD Rokkor-X 1:1.7 50mm on a SRT 201. What are basic differences between these lenses other than the focal length?

There is a problem with the MC. Off the camera, the apperature stays at maximum when you turn the Apperature Ring to a smaller opening. On the camera, the Stop Down button will not close down the opening. I can get the opening to stop down only by removing the lens and moving the small lever on the back that couples with the stop down button.

Comparing the MD on both cameras, It looks like the 201 stops down when the button is pressed and opens back up when the button is released. The 101 appears to stop down and stay there until the stop down button is pressed again.

Good morning, John;

This is a followup or backup message to supplement the one also left under 35mm Cameras under the Equipment Forums. A quick synopsis of that message is: The 55mm lens needs repair. And, it is worth a repair.

Regarding the length of time to get a reply to a question given on this forum, one day is not really too bad. While there are many people here who do have experience with and knowledge of Minolta cameras, most of the people cannot monitor this forum due to their also having a day job. Unfortunately, supervisory and management types seem to feel that the people there should be concentrating on the tasks and goals of the organization, and not participating in forums of this type which they feel are basically recreational in nature.

Regarding the question about the differences in the two lenses, other than the focal lengths, they are really very similar in many ways. From the description you gave, the MC could be from 1969 to 1972, and the MD from 1973 to 1976. Both of them are 6 elements in 5 groups design. Both of them are in the old school of lens construction which includes mainly metallic construction materials. Their lens characteristics (resolution, contrast, flare resistance, color, et cetera) are fairly similar also. The main difference in the later lens is the slight change in the focal length to more closely conform to what most people feel that a "normal" lens should be (although I have differing thoughts on that very subject), and to adapt the lens mount to the two-tab configuration of the MD mount to allow it to work more conveniently with the Program Mode of the X-700 series of cameras. As you are using the lenses on two SR-T model camera bodies, this mount difference is of no consequence to those SR-T bodies. The SR-T bodies are looking only at the MC tab. Both of the lenses are of a similar vintage, and they are similar in performance. The coatings on the lens elements will also be similar, although the coatings on the MD lens could be incrementally better. Minolta had a practice of improving the lens coatings when the engineering staff were satisfied that they had a better coating, and they went to the improved coatings when it was expedient to do so. They did not wait until a "year end point" or a "model change" to implement the new coating process. It is quite possible that your lenses have exactly the same coatings if the 55mm is a late production and the 50mm is an early production in each series.

Again, I think it is worth considering having the 55mm MC lens aperture repaired.

Enjoy;

Ralph
Latte Land, Washington