The Minolta 40-80mm f/2.8 Gearbox Zoom; The Clockwork Lens



There have been giants within the earth in these days . . . They have been mighty males, males of renown.  Genesis 6:four

I’ve all the time been fascinated by the historical past of lenses. I write about it a lot. To me, probably the most fascinating gadgets are these made a few years in the past, with what we might think about wholly insufficient know-how, which did issues we will hardly reproduce immediately.

Not way back, I discovered of a lens I’d one way or the other missed, the Minolta MC Rokkor X 40-80mm f/2.eight zoom(1, 2, 3).  Let’s pay somewhat respect to the innovation of this lens. It’s an f2.eight zoom, however has an solely 55mm entrance component diameter, is about 10cm (four inches) lengthy, and weighs 560 grams (simply over a pound) regardless of being all-metal development. From many reviews and examples, it has wonderful picture high quality.

Additionally it is utterly distinctive (so far as I do know) in being the one zoom lens pushed by an exterior gearbox. There have been a number of telescoping zooms. The primary zoom, the Voigtlander Zoomar, used a sliding ring set on thick rods. Virtually all different zooms have used a rotating helicoid to maneuver the zoom teams.

However solely the Minolta put a mechanical field on the aspect of the lens to drive the focusing and zoom parts., 2016

Shifting the lever together with your thumb to zoom the lens, spinning the wheel together with your fingers focuses it, and shifting the metallic thumbscrew on the backside out and in, places the lens in macro mode., 2017

So once I received my arms on a replica of this distinctive lens, I had two questions. First, was it nearly as good as they are saying it was? Second, how the hell does that gearbox factor work? Fortunately, we had the capabilities to reply each questions.

Optical Testing

We didn’t have precisely the best lens mount for this lens however have been capable of make one thing work. At 40mm, although, the very edges of the check circle have been reduce off, however nonetheless, at 40mm and f/2.eight this can be a fairly spectacular efficiency for a 40-year-old zoom lens.

Olaf Optical Testing, 2017


At 80mm issues have been much less spectacular. This can be a 40-year previous lens, and issues might have occurred to it that affected efficiency, however additional checks confirmed no decentering or subject tilt. Nonetheless, it’s potential there’s a spacing error on the lengthy finish of the zoom vary.

Olaf Optical Testing, 2017


When we stopped right down to f/5.6 at 80mm, although, we have been fairly impressed once more. (This makes me assume it unlikely that there's any actual optical maladjustment right here, it cleans up too properly at f/5.6 to have a serious optical difficulty.)

Olaf Optical Testing, 2017


My abstract is it seems simply like an excellent movie zoom from the 70s can be anticipated to look. It’s fairly good on the broad finish, must be stopped down on the longer finish, however general is a really usable lens. To get that in such a small package deal with macro capabilities, properly, that’s spectacular.

Of Course, We’re Going to Take it Aside

Be affected person, although. We’ve by no means seen a lens even barely like this, so we have now completely no concept what we’re doing at present. Most days we have now a minimum of a obscure concept.

We had two hints, although. First, the lens is roofed in a pleasant leatherette, like a digital camera physique of the occasions. Leatherette is often there to cowl screws. Second, we might see some set screws across the barrel. You don’t see set screws in lenses as we speak fairly often, however whenever you do, properly, they should come out.

So We Began with the Apparent

We eliminated the three set screws across the rear barrel., 2017

We have been type of impressed with these 1970’s set screws. As my buddies from Boston would say, ‘they’re depraved sharp.’, 2017

With the set screws out, a rear ring, we’ll name it a make-up ring, got here off., 2017


With that out of the best way, we might see some actual screws beneath., 2017


Taking them out appeared a logical subsequent step., 2017

After eradicating these, Aaron might slide off the aperture management ring. We have been beginning to really feel a bit of assured now. That confidence, as you will notice, was completely misplaced., 2017


The aperture management meeting is fairly routine. There’s a comparatively lengthy slotted key that inserts into the aperture ring. You'll be able to see a spring beneath it and a counter spring on the opposite aspect., 2017

&, 2017

You might have observed the thick, brass spacing shim underneath the aperture ring. It’s in a location the place it might be an adjustment for infinity focus, however we aren’t sure given its thickness. It'd simply be a normal, non-variable spacer., 2017


Then We Got here to a Fork within the Disassembly Street

With the aperture management meeting off, there was a rear group protruding that seemed prefer it could possibly be eliminated., 2017


There was additionally a rear metallic plate that appeared prefer it was product of tarnished copper. There have been a few screws within the plate that appeared as if they needed to be eliminated. You might also discover the three black plugs within the plate. We weren’t positive what they have been, however assuming the shifting parts slid alongside some sort of rail, we thought that could possibly be the rail ends., 2017

Whereas we determined which strategy to go subsequent, we performed round with the gearbox a bit, as a result of with the rear of the lens barrel off you will get a pleasant, clear take a look at what the silver thumbscrew lever does. Turning it and pushing it in strikes the lens’ optical meeting ahead, principally like placing a built-in extension tube on the lens., 2017, 2017

This was accomplished by Minolta in 1975. It was executed once more in 2013 when Canon launched the 24-70mm f/4 IS Macro. (Mock me should you should, however the 24-70 f/four IS is the lens I exploit most.) Minolta, within the 1970s and 80s, was arguably probably the most progressive digital camera firm, with Nikon and Canon typically enjoying catch-up.

Anyway, after enjoying round with the Macro button and turning the main target knob and zoom lever some extra, we determined ‘neither of the above’ was the best choice and began taking out the screws from the mechanical field cowl. That is totally different for us as a result of in contrast to as we speak’s lenses, the screws have been slotted, not JIS. We needed to hunt round for a bit to seek out the best screwdriver., 2017

Eradicating the screws loosened the field, however it wasn’t going anyplace as a result of the zoom lever and focusing wheel have been nonetheless fastened in place.  The little bit of leatherette on prime of the focusing wheel appeared unlikely to only be ornamental., 2017

So we peeled it off., 2017


And positive sufficient, there have been some good huge screws underneath there., 2017

The main target lever lifted proper off as soon as these have been eliminated., 2017


After that, we might raise the mechanical housing off. Discover that the middle submit, which controls zoom, continues to be a part of the lens. The main target ring and macro thumbscrew mechanisms are a part of the housing we took off., 2017


Properly, How Do I Work This?

In the event you don’t like fascinating mechanics, you'll be able to skip this half. However we'll all assume much less of you in case you do.

Let’s begin with the case we simply eliminated, which accommodates the macro and focusing mechanisms, each of which transfer what, for lack of a greater time period; I'll name the Magic Slot (pink arrow) within the prime case. As an apart, I might very very similar to to purchase whoever designed this a beer. This, my pals, is a mechanical artwork of the very best order., 2016

I’m going to compress the pictures a bit to point out you ways issues work. First, once we transfer the lens from normal (thumbscrew out) to the macro (thumbscrew in) place, we transfer the highest aspect (within the image) of the lever ahead., 2017

If we rotate the focusing wheel, we transfer the decrease aspect of the lever ahead or backward. Closest focus is the picture on the left under, infinity give attention to the proper., 2017


For those who assume that’s somewhat complicated, perhaps displaying you what the Magic Slot does to the lens will assist. Or perhaps not.

The inexperienced arrow factors to the zoom stem, popping out of the sector towards you. The pink arrow is pointing to a heavy obligation brass publish coated with a white bumper, which I'll name the Golden Submit (as a result of regular lens phrases like helicoid and cams don’t work right here). The brass base of the golden publish slides up and down (within the image’s orientation, it will be side-to-side on the lens) the 2 aluminum rods. And the rods are related to the massive aluminum base plate you see under every part else., 2017


The Golden Publish inserts into the Magic Slot we confirmed you above. As we simply identified, the Magic Slot strikes ahead and backward if you flip the focusing ring. This strikes the Magic Submit and subsequently the aluminum baseplate, which is hooked up to the lens’ optical system ahead and backward too, focusing the lens.

The copper plate with the curved slots rotates if you flip the zoom lever. (Helicoid plate sounds ridiculous, and I attempt to not use ‘thingie’ in these posts, so I’m going with a copper plate.)

You'll be able to see the 2 cam screws on the shut ends of the slot within the footage above and under. These transfer the zoom parts when the copper plate rotates. Aaron’s forceps are pointing to one of many cams within the image under, proven with the lens zoomed about midway. We truthfully had assumed there was some sort of worm-gear driving the zoom mechanism, however that is similar to the slots you'd see within the rotating barrel of a traditional lens., 2017

On this place, you may also see a publish with a black bumper that's sticking up from the copper zoom plate inserting into the bottom of the Golden Publish.  There’s a closeup within the picture under., 2017

The place of the zoom slides the brass focusing submit from one aspect to the opposite alongside the rails. The focusing submit is sliding inside the Magic Slot, the place of which has been adjusted by the focusing ring and the macro thumbscrew. So the submit isn't solely sliding from side-to-side, however additionally it is shifting ahead and backward relying upon the place of the magic slot., 2017

So issues work this manner:

  1. The focusing ring (and the macro thumbscrew) transfer the Magic Slot in the direction of the entrance or again of the lens. Because the Golden Publish is within the Magic slot, your complete lens meeting strikes together with it, focusing the lens.
  2. When the zoom plate rotates, it strikes the 2 zoom parts additional and nearer from one another, zooming the lens.
  3. When the zoom plate rotates, it additionally slides the Golden Submit alongside the Magic Slot, readjusting its focus place.

That is an intense little mechanical pc. Altering the focal size mechanically modifications the main target to an applicable location. Some trendy lenses do one thing comparable, the place a collection of keys contained in the lens transfer the focusing group when the lens is zoomed. Others do it with digital programming within the lookup tables.

However that is easy and stylish. OK, perhaps it’s simply elegant. I’m fairly assured a variety of engineers wiped out loads of slide guidelines figuring all this out, however as soon as the calculations have been made, the mechanics make all of the corrections routinely and will maintain the lens pretty parfocal when zooming.

As an Afterthought, Let’s Take Aside the Lens

Clearly, I used to be most concerned with how the zoom and focus mechanisms labored on this lens, however so long as we’re right here, we'd as nicely take the damned factor aside. I might say we needed to wash and lubricate it, however you’d all know that’s a bald-faced lie. There have been screws not eliminated and that makes us a bit loopy.

Anyway, by rotating the zoom plate, Aaron might entry the screws that maintain the mechanical meeting to the lens., 2017

And take away it., 2017


With that off, we will see how the zoom teams transfer. Should you scroll again as much as one of many footage of the copper plate, you'll be able to see the 2 cams of their slots within the plate. With the pate eliminated you possibly can see how every of these parts strikes when the plate rotates., 2017, 2017


Now I might subsequent present you a dozen footage as we tried to, so as, take away the entrance ring, take away the copper ring from the again, take away the zooming cams. Properly, we tried all of these issues, however the lens didn’t disassemble. It rattled some however didn’t come aside., 2017


So subsequent we went with Aaron’s Second Rule of Disassembly: All leatherette have to be eliminated., 2017

This gave us entry to good, thick bolts that held a lot of the fastened parts in place. We eliminated these, in fact, which wasn’t, maybe, the most effective concept. (Truly it was our greatest concept, on the idea that it was our solely concept. It simply wasn’t a good suggestion.) When the primary bolt got here out, we heard the fairly sickening sound of a nut of some sort falling into the lens. This, my pals, was the purpose of no return. Now we needed to get the lens disassembled, even when that meant utilizing a round noticed.

Appearing like we have been cool with all this, as a result of individuals have been strolling via the restore area, we took out the remainder of the bolts, after which we have been capable of slide the entrance group part-way out of the lens. It was good to see, even at 40 years previous, there was a pleasant felt ring defending the insides of the lens from the outsides of the world., 2017


It will have been nicer to see the optical group simply slide proper out. However, in fact, like the whole lot else about this lens, issues weren’t as we anticipated. Our final obscure hope was that, with the entrance group partially out of the lens, some extra set screws have been uncovered., 2017

And after eradicating these, we might unscrew the entrance aspect from the remainder of the entrance group., 2017

And, as you could have observed within the image above, this created sufficient of a gap to allow us to drop the ‘nuts’ out of the lens. All eight of them., 2017


With the entrance group eliminated, we might see the remaining parts slide up and down on three comparatively thick rods (you possibly can see the ends within the picture under, and the rods themselves within the subsequent image)., 2017, 2017

However the rods run contained in the internal barrel. To get the outer barrel off, we nonetheless needed to take away the focusing cams from their parts. We ultimately completed this, utilizing a number of purposes of glue remover, warmth, and torque., 2017


Lastly, with these eliminated, we might slide the internal barrel out of the outer casing. These previous couple of footage characterize about an hour of time and a radical and full use of our full lexicon of unprintable phrases., 2017, 2017


This gave sufficient entry in order that Aaron might get a grip on the second factor and unscrew it., 2017

There have been a number of spacing shims beneath that second group, which is the one true optical adjustment we discovered on this lens., 2017

Now, with all the entrance optics eliminated, we have now an unobstructed view of the aperture blades. They appeared identical to aperture blades, and at this level, we have been glad to see one thing that seemed acquainted., 2017

We went to the again of the lens and eliminated the screws from the copper plate (nicely, copper wanting, I don’t assume it’s copper) on the again as a result of these have been the one screws left.  In fact, it will not come off over the rear factor., 2017

Pulling it again did expose the rear finish of the rods passing by means of the lens although, so we eliminated the set screws holding the rods in place., 2017

Then lastly discovered extra set screws on the entrance of the optical barrel, beneath the felt., 2017

With all of the set screws eliminated we might push the rods up from the again., 2017

And instantly we have been accomplished! With the rods moved up, the rear group slid proper out. On reflection, we might have carried out this rather a lot earlier and saved, nicely, time, sanity, and curse phrases., 2017

There was, in fact, yet one more set screw to take away., 2017


After eradicating that, the aperture meeting unscrewed from the rear group., 2017


And solely then might we take the rear group out from the copper plate., 2017

There was no cause to separate the rear group, so instantly our disassembly was full. (OK, you’re proper. There was no cause to separate any of these items, besides that’s what we do.), 2017

So What Did We Study At this time?

That there have been some slick engineers engaged on issues at Minolta again within the 1970s, considering means outdoors the field. This was a completely totally different means of creating a zoom.

I do not know why this didn’t catch on. It was smaller and in some ways easier than competing lenses. It was, maybe, too totally different. Or perhaps simply too troublesome to assemble and disassemble (though I’m sure there have been simpler methods to do it than our fumbling about). It may need been costlier to make. Or perhaps it was too pricey to maintain making one clockwork lens when the others all used routine zooming and focusing strategies.

Nevertheless it’s a powerful instance of some engineering gone wild, and I all the time love seeing designs which are outdoors of the field.


Roger Cicala and Aaron Closz

September, 2017


Addendum: As a result of many individuals have been nervous we wouldn’t be capable of get this basic lens again collectively once more: