Button on MC Lenses

I just picked up 28mm, 55mm, 135mm, and 200mm MC lenses with a SRT 101. The 28, 135, and 200 all have a silver "button" or "lever" on them. The fellow that I got them from, who had bought them when he bought his SRT 101 in the early 70's, couldn't remember what they did. I have several MC/MD lenses of assorted lengths, and none of them have this feature. I cannot figure out what they are for. I wonderd if they were a manual way to shut down to the set aperture on non-metered Minoltas, but they don't seem to do that.

The 55 and 135 have the typical symptoms of gummed up lube. Have any of you ever gotten inside one of these far enough to loosen them up? I got the lenses for nothing since they had the problem so am not out anything if I mess one up. And I might learn something in the process.

Hi John,
The buttons and levers are for stopping the lens down to the chosen aperture. They have the same function as the stop down (depth-of-field check) button on the camera. The lens needs to be mounted on the camera for this button or lever to work, because the lens aperture just goes to whatever it is set at without the camera to hold it open to maximum aperture for composition and focusing. I think the button is a holdover from the earlier SR-series cameras that didn't include the button on the camera, as I've never seen an SRT-series camera that didn't have the built-in one.
Best regards,
Mike

I put one of them on the camera and sure enough, it does just as you say. Thanks.

Good morning, John and UpNorthCyclist;

Yes, we old guys with the SR-2, SR-1, SR-3, and SR-7 cameras remember those levers on the side of the SR lenses back near the lens mounting flange. (The cameras are listed in order of appearance. That is not a mistake in the typing.)

Enjoy; Ralph, Latte Land, Washington

Hi again, John and Ralph,

Ralph, you are dating yourself with your knowledge of the SRs - my first good camera was an SRT-102 bought new when I was, like, 24 years old - and I'm a geezer now...

John, since no one else has jumped in - I've disassembled a couple of junk MC lenses. The problem is, once you get to the heart of the matter (gunky aperture blades), with the ones that I've fooled around with, you've spoiled the calibration of the lens and it takes a fancy gizmo called a collimator (sp?) to make it right again. On some lenses, if you go in through the front (you need a lens/spanner wrench) you can get to the front of the blades but not the back. You can't clean and regrease the helical that way, either, which is usually where the grease that seperated over time, causing the problem, came from. Going in from the rear of the lens, you'll be dealing with a bunch of pesky springs and teeny things like the ball bearing on a micro-spring that clicks in the lens' f-stops. Eventually, you'll run into some screws that are glued in place - these secure the plate that locates the lens elements in relation to the helical, which determines where the lens focuses in relation to the film plane of the camera and the markings on the lens barrel. Once you move those, the lens is toast unless you have the means of redetermining the focal plane - hence the collimator. It may be possible to mark the original position of this plate somehow, but once you reassemble the lens, everything is going to have moved a bit and it probably won't be perfect.

The four lenses you describe - a great kit, by the way - are probably the most common ones that Minolta made in the SRT-101 era. Minolta made several grades in each of these lenses and as long as you aren't interested in the fastest grade they made they can be had for very reasonable prices and are still sharp, excellent lenses.

S-o-o-o, have fun disassembling them - I'm kind of a klutz so there's a good chance you'll have better results than I did!

Best regards,

Mike