Lenses

Minolta SR lenses NOT the same as MC/MD

OK, So everywhere we see the ads, mostly on eBay, where Minolta SR lenses (the ones called Auto Rokkor, with ‘W’ for wide or ‘Tele’ added on) are broadly equated to MD-Fit or something similar. Beware! This is not necessarily so!  The very early lenses do FIT ON the Minolta Bayonet, but DO NOT STOP DOWN to their minimum aperture. This has physical reasons, which I shall explain.

This means that the first series of these lenses attach correctly (the Minolta bayonet stayed the same until Auto-Focus came along) BUT the lenses only stop down on the later cameras to an aperture of around f8, no matter what you pre-set on the lens. This is due to the placement of the lever inside the cameras and lenses, that are, to put it simply, in different places! From f8 upwards in the direction of ‘more open’ I have found no limits and the restriction does NOT apply to fitting to Digital cameras with adapters that anyway don’t stop down, which is great news.

Take a look why: I have taken shots of an early SR1 (‘b’ series) from 1960 and compared it to the mount on the SRT* (in this case a 303) when the ‘MC’ notation was introduced. Note the placement of the lever at the bottom of the mount, that closes the lens down at exposure.

Firstly here, the back of an SRT/MC/MD Mount lens on the left compared with the early SR (Auto Rokkor without the MC/MD) mount lens on the right. You will note the difference in the placement of the Iris-Lever, although both are stopped down to f22. What you can’t see, is the range of travel of the lever for the lens on the right, which is almost the whole arc as drawn in. compared to the tiddly bit which is obvious in comparison on the left lens (physically limited by the slot it can move in axially – less than half of the arc); on the later Auto Rokkor lenses, from about 1960, the stop-down lever for the iris is the same as for the MC lenses and will work perfectly on later cameras – definitely any camera made after 1961.

Below the positions of the actuating levers inside the back of the mount on the cameras themselves can be seen. The SRT 303 is representative in its proportions of ALL manual Minolta mounts up until the introduction of the Auto Focus mount.

In this picture, the lens would be STOPPED DOWN, on the SRT using the button on the side of the mount and on this early SR (1959) by simply not cocking the shutter – fully automatic diaphragm came in 1961 when both the SR3 and SR1 got the modification. The difference in the position at maximum deflection is pretty obvious.

The same two cameras when the aperture is held open: Actually identical.

Here we have both cameras with the lens mounted and stopped down to f22. I think the difference speaks for itself. The picture speaks a thousand words?

The SRT manages just smaller than f8. This will happen to ALL Auto Rokkor lenses if mounted on SRT and later cameras (actually any Minolta after at the latest 1961, when the automatic diaphragm was introduced). The other way around, ANY Manual lens will work correctly on the earlier, pre-SRT cameras and of course with any of the Digitals, too – with an adapter.

So, it’s up to you, but buying the earlier lenses, with very few exceptions, is not better than a comparable MC or MD, despite being cheaper (mostly). Quite apart from the mentioned deficit in the usability on later cameras, for the most part the performance and definitely the coatings just doesn’t make it worthwhile – unless you have the very much earlier cameras! The thing to look out for to positively identify the first series of lenses is the flat ring on the back of the lens without the ‘window’ for the iris-coupling, as clearly shown in the pictures above. Another indicator, if not definitive, is the aperture-ring with the engraved yellow ‘LV’ values below the f-numbers. Some, however, even with these engravings also had the later mechanism 🙂

The SR-2 and both ‘a’ (first series with ‘lift-up’ shutter-speed dial) and ‘b’ versions of the SR-1 without the meter block all have the long-travel lever, but in 1960 alongside the introduction of the SR-3, there was also a ‘plain’ SR-1 (‘c’) without the block, but with the automatic diaphragm…

Vintage 135mm f2.8 with sticky Aperture Blades

This is one of the rarest lenses that I have had the pleasure to work on: a 1958 Minolta Auto Tele Rokkor with yellow LV engravings, apparently less than 2,000 ever made, to coincide with the release of the new SR2, Minolta’s first SLR in a long line, with loads of new features. I digress. The lens is a 7-lens construction and actually very good even by today’s standards. Not as clinically sharp as the much later 5- and 4-lensers, but still very nice.

This one is outside very pretty, the problem with it is that the iris had oil on it, making it rather sluggish. Not SO much of a problem, but definitely needed looking at to use it regularly.

Actually quite easy to dismantle (I never had one of these in my hands yet!) and the solution to the problem, largely due to the iris assembly being in the centre of the lens, was also simple enough.

There are a few things that can be done incorrectly regarding the order of dismantling – guess how I know – so it would be wise to stick to the order given as follows:

1: Undo the three black screws round the aperture ring. The one at this spot is the longest and belongs back here on reassembly. Inside the ring there are tiny balls that detent into the slots on the barrel (as can be seen on the picture) to give those snappy click-stops and to smooth the turning of the ring. Don’t lose them! A spot of grease will hold them on place for reassembly.

2) Remove the three silver screws around the barrel, which then can be easily pulled off the front.

3) The front lens element needs to be taken off next to access the blades. Do this CAREFULLY and with the PROPER TOOL, otherwise you risk scratching or damaging the ring, or MUCH WORSE, the lens, which if it is in good nick, will be almost impossible to replace in a hurry. If you have undone the grub screws by accident due to impatience or curiosity, you will now reap the reward by having a pile of separate (thankfully only six) aperture blades rattling around the inside! Oh Joy! Never mind. The construction is so simple and needs no explaining here, apart from to mention that a steady hand and a pair of nice pointy tweezers do come in handy 🙂

At this stage, you should be able to see the blades and what condition they are in. If they are only oily, then no further dismantling is necessary and they can simply be washed with a paintbrush dipped in some Methylated spirits or lighter fuel. While doing so, you can wiggle the stop-down lever thingy, to make the blades move open and closed, so they get a good rinsing. Be careful not to use too much meths and splash the rear lens from the inside. If you did, then you need to disassemble a bit more from the back (see further down) and wipe the lens properly using a moist lint-free cloth.

READ THIS FIRST BEFORE GOING ANY FURTHER: If you haven’t already done so, turn the whole assembly so that you are looking down the front at the blades. NOW, AFTER you have marked the position of the outside ring in the barrel, you can at last undo the grub screws and take out the inner ring holding the blades in. When you undo the grub screws, the outside ring could rotate, so mark it BEFORE you undo even one screw. The position of the outside of the ring is critical to the iris opening and therefore the exposure, so please don’t forget this.

Now you can remove the parts carefully with preferably copper tweezers (make your own!) and clean and inspect properly, prior to reassembly – with cotton gloves on, please: fingerprints on the blades are so unprofessional!

OK, so yours, like mine were not only oily, but one was a bit bent? I can only assume that someone else with good intentions tried to fix it years ago and oiled them for good measure, but was not very light handed with reassembly. It’s always only ONE blade that gets bent, the last one, since it has to be tucked under rest that are already in place – a bit like Escher’s endless staircase! You know how to do it, if you have ever closed a cardboard box by overlapping the ears on the lid: Same principle, if a bit smaller. It will be obvious when you get that far. Not much is needed to make the blades ‘sluggish’ due to the added friction and no amount of oil helps (it in fact makes it worse, as we now know).

This is what they look like when reassembled through the replaced front lens. Reassembly is simply the reverse of the dismantling job, not forgetting to place the long screw where it belongs. In this picture, you can just see the nick on the top screw slot on the lens-ring, where I slipped despite having the correct tool – the lens was VERY tight. I suspect that it was secured with Loctite or similar.

Here a bit closer, in focus and nice and clean!

So, just because we are curious and maybe because we spilled meths on the rear element, or to get at the mechanism and to be able to not only disassemble but also adjust, the rear end has to be taken off. There is actually no reason to NEED to disassemble further, as everything for the aperture blades can be accessed from the front, but since we got this far, here goes:

4) Remove the rear mount (4 screws)

5) Unscrew the tube and rectangular hole (!) around the rear lens and put them out of  harm’s way.

6) Now you can safely unwind the focus-ring and PLEASE note and mark the spot where it comes off the thread to realign it when reassembling. Time consuming if you forget and have to find the right spot by trial and error – there are lots of possible ways to start the thread (8, actually). Once off and with the simple barrel at the front removed (3 screws), this is what it looks like:

The red arrow shows where the end of the spring belongs when the rear end is reassembled – tucked INSIDE the front tube/barrel when replaced!

In the above picture, the stop-down-knob is around the back, hidden by the rear lens element in this shot, but this shows the arrangement of the spring on the lever which actually causes the iris to open and close. Its function will be obvious when you actually have it in your hand and actuate the stop-down. It also shows the rear element which can simply be unscrewed to clean.

Reassembly:

7) Put the blades back together carefully (especially the last one), arranging firstly the blades the only way that they fit – yes, there is only one way! – and then placing the front ring over them and aligning the pins on the blades in the slots/holes provided.

8) Line up the outer ring with the mark you made OR look for the bright-spots/ dents in the aluminium where the grub-screws originally were. You might have to turn the ring once or twice, since there are three possible positions 🙂 Replace the grub-screws and make sure that they pinch not too tight, but hold everything in place.

9) Now you can test the freedom of the blades by twiddling the stop-down-knob.

10) If all is OK, replace the front end complete with aperture-ring and lens as a reversal of the disassembly. If not, try again!

11) Fix the screw-thread for the focus in place and the front tube/barrel, not forgetting to tuck the little spring inside by the stop-down-thingy before securing the 3 screws.

12) Position the outer focus barrel to screw onto the inner thread in the right place to enable to focus full length without fouling the stop-down-lever (you marked the position, remember?). If not, it’s trial and error time, looking at the bottom of the thread-travel for the stop-down-button to sit where the swept cutout is in the front edge of the barrel.

13) Once you have managed that, replace the rest of the parts around the rear lens and the mount and you are done! (Oh, and you’re a HERO, too! Have a beer/coffee/tea/wine/lemonade/schnapps!)

Actually a lot simpler than it was to describe, so have a go. You can pick up a similar one of these lenses for not much more than a tenner (if you find one with the yellow numbers engraved, BUY IT, KEEP IT!) to practice on, so don’t be afraid. What I haven’t shown in pictures here is self explanatory when you are doing it ‘live’, so don’t be intimidated.

Have fun!