VMLP 1: A Visual Guide to Minolta Lens Mounts—SR to A

This is the first Vintage Minolta Love Project (VMLP) post. To learn more about VLMP, read this.

Last year, I bid on a 35-105mm RMC Tokina lens intended for use with my recently-acquired Minolta X-570. There were plenty of pictures. When the lens arrived, I spent 10 minutes trying to attach it to my camera, but it wouldn’t fit. Looking closely at the lens, I found it had “k/pk” at the base—it was a Pentax lens!  

I went back to the site pics, and sure enough, it was the same lens. The listing said “Minolta MD,” but the pictures were for Pentax. It was only 9.00 and not worth returning, so I still have the lens. That’s when I decided to learn how each lens mount looked and avoid another buying incident. (It helped too; I almost bought a mislabeled Nikon lens for a lot more money). 

Minolta made a lot of 35mm lenses, and fortunately, there are sites that discuss them in all their glory (Minolta Lens Index). My interest in mounts moved beyond spotting errors to a fascination with Minolta’s design prowess when I became interested in manual focus cameras. That interest began as a historical curiosity and ended with me tracking down and buying the Minolta SR-2, the first Minolta 35mm SLR. The final push to learn more about Minolta lens mounts came from a 100-200mm 5.6 zoom lens an eBay seller threw into a lot just to get rid of it. It is an odd looking lens, a black and silver pipe that does not behave like my other lenses. After a lot of searching and asking questions on forums, I learned it was a preset lens from the 60s. Next, I bought six books that cover Minolta gear, and the quest was on!

The information and images presented here are the outcomes of my research. They illustrate the progress Minolta made from fully manual lenses to those that support metering and autofocus. This is a brief primer for those new to Minolta products. For more exhaustive information, see the suggested references at the end of the post.

SR Mount
The SR Mount, introduced in 1958 with the Minolta SR-2, used a bayonet design. According to JD Cooper (1), six lenses were available for the Minolta SR-2 in 1959 —three Auto Rokkors (35mm HG f2.8, 55mm PF f1.8, 100mm QE f3.5) and three manual preset lenses (Tele Rokkor 135mm PG f2.8, Tele Rokkor 180mm PF f2.5, Tele Rokkor 250 mm QF f4) that had the mount used for my 1965 100-200mm f5.6 preset zoom.

Metering was done using external devices, so the lens and camera were unaware of light conditions. The bayonet consists of three separate winged sections, one with a notch, which allows the lens to lock in place on the camera.

The Auto Rokkor lenses introduced with the SR-2 were referred to as “Automatic.” Here, automatic meant that the lens stopped down when the shutter fired, then reopened to full aperture when the film was advanced (1, 2, 3). The first time I used the SR-2, I forgot about this design feature and panicked when the viewfinder stayed so dark after the first shot.   

The Auto Rokkor 55mm 1.8, pictured here, is a later version of the one released with the initial group of lenses for the SR-2. In order to provide automatic operation, the lens has an aperture pin that contacts a lever inside the camera body. The aperture pin permits the camera to keep the aperture open to its maximum size until the shutter is fired. This was a major innovation in 1958. The image of the Auto Rokkor 1.8 shows the bayonet mount with the locking notch at the 12 o’clock position. The aperture pin is just below the notch. Cooper warns that some SR-1, SR-7, and SR-3 cameras cannot be used with some auto lenses produced early on for the SR-2 and SR-1 unless they have been adapted (3). I have not been able to determine what that means. It’s probably moot as I have yet to see an Auto Rokkor 55mm 1.8 with a serial number early enough for this advice to matter. 

Minolta also produced preset lenses (2).  Preset apertures have to be manually stopped down and reopened.  Here is my Zoom Rokkor 100-200mm f5.6. It has the bayonet mount but lacks the aperture pin.  

Meter Coupling — MC
When Minolta released the SR-T101 camera in 1966, it had a built-in light meter. As such, the lens design changed to communicate the lens aperture to the camera. It was accomplished by adding a small tab on the lens’ aperture ring (2). (In the image, it is the silver tab just above the notch in the bayonet wing).

The SR-T 101 also sported a new feature, a tab on its body that communicates the aperture to the camera’s meter. Minolta called this design change “Meter Coupling” (MC). This MC Rokkor 55mm 1.8 lens shows the MC tab at 1 o’clock position, and note the tab on the SR-T 101 body. The Minolta XK was the first Minolta to show the aperture in the viewfinder. 

Minimum Diaphragm — MD
The Minolta XD camera was another innovation first for Minolta. XD cameras offered both aperture priority and shutter priority operating modes (2). This flexibility required that the camera be able to know the minimum aperture available for shutter priority shooting. This “MD” or minimum diaphragm ability was added by placing a second tab on the lens (2), seen at about the 2 o’clock position on this MD Rokkok-X 50mm 1.4 lens. Like the SR-T family, XD camera bodies also have an additional tab that contacts the tab on an MD lens when the lens is set to its minimum aperture.  

A Mount
In 1985, Minolta introduced the Maxxum 7000, the first camera with body-integrated autofocus capability. Minolta shelved the SR mount and moved to the new “A” mount that provided the information required for accurate autofocusing and metering. This 35-70mm f4 lens shows the original A mount design. It is a bayonet design, and the lens has a screw at the 7 o’clock position, which engages the camera’s focusing motor (4). Five electrical contacts, seen at the top of the photo, match those in Maxxum camera bodies.  

ADI
The final change to the A mount lens architecture was the addition of three electrical contacts seen in this 75-300mm D lens. Lenses with eight contacts are referred to as “D” lenses as in Advanced Distance Integration (5). ADI was touted as a way of improving flash performance by providing more detailed information to the camera.

ADI flash and D lenses arrived with the Maxxum 7, Minolta’s technological marvel. One notable feature seen when using a Maxxum 7 with a D lens is the display of detailed depth of field and distance to subject information on the camera’s rear LCD. I love this feature!  

Well, that’s the tour! The info presented here is enough to allow anyone to quickly identify Minolta lenses by their metering and autofocusing features. I hope the information offered here helps both in understanding Minolta lens terminology and avoiding buying mistakes. Happy Minoltaing! (Yeah, it’s a word—or, at least it is now.)

  References
1. Cooper JD. The Minolta Manual, Verlan Books, NY, New York, 1959

2. Reynolds C. The Minolta Way: The Minolta SLR Photographer’s Companion. Focal Press, London, UK. 1979 

3. Cooper JD.  Official Minolta SR Manual: How To Use The SR-1, SR-7, And All Previous Models.  Universal Photo Books, New York, NY. 1965 

4. Shipman C. How to Select and Use Minolta Maxxum Cameras. HP Book, Los Angeles, CA 1989. 

5. “What is ADI Flash Metering?” Alpha Strobe Users Portal, https://alphastrobist.wordpress.com/what-is-adi-flash-metering/

Websites for additional lens information:
Manual Lenses
Subclub.org/minman
Henrik Robeck’s Minolta Site

Autofocus Lenses
Kurt Munger 
Dyxum