remove detents from OM lens

BetterSense · Apr 16, 2016

I want to make the aperture ring on my OM 50mm lens turn smoothly without detents.

Does anyone have any exploded views or knowledge of how these lenses are put together so I can get some idea where to start?

Ricardo Miranda · Apr 16, 2016

The question is why do you want to do that?
Please, don't answer if it involves the D word.
I just want to make you think twice before you destroy a perfectly good lens.

You should find what you need here: http://olympus.dementix.org/Hardware/olympus_hw.html
Good luck!

Sirius Glass · Apr 17, 2016

+1

Not the worst, but one of the worst DIY ideas that I have seen in a while.

MattKing · Apr 17, 2016

My guess is that the OP wants to use the lens with an adapter on a different sort of body, for video work.

The video lenses frequently have no detents on the aperture ring.

btaylor · Apr 17, 2016

Yes, removing f stop detents is a service some cinema lens shops provide. A problem with using still camera lenses on cinema cameras is the short focus throw among other things. But with a single cinema prime going for 5 to $30k each, one can see the attraction. Duclos does a good business with the conversions.

shutterfinger · Apr 17, 2016

The detent is usually a small steel ball on a spring that seats into a recess on the ring. Leaf shutters sometimes use a raised portion on a metal flange to mate with the recess on the plate. Detents can cause some intermediate stop positions from being usable as the detent will snap the aperture to the closest half stop or whole stop. If one is doing fine exposure computations then 1/6 to 1/3 stop adjustments are desirable but not accomplishable due to the detent. Shortening the spring a few thousands may achieve the desired result of an infinitely adjustable aperture with click stops that do not interfere with a 1/6 or smaller stop position close to the detent position.

baachitraka · Apr 17, 2016

Helios 44-2 lens.

No mods on Zuikos please.

BetterSense · Apr 17, 2016

The lens is indeed destined for an "alternative" application, but it's still an analog one. I'm making a motor-driven aperture, and I think the click stops will interfere. The main reason to use a Zuiko lens is that the aperture ring is on the front of the lens. Any other lens with an easily-turned aperture ring would also work; but I do need a body to go with it too and I happen to have a "parts" OM1.

Hilo · Apr 17, 2016

A very interesting lens without detents: the Zeiss Ultron 50/1.8 with concave front element. Comes with Icarex BM mount, or in M-42.

BetterSense · Apr 17, 2016

I also thought about enlarger lenses many of which have large and smooth aperture rings. However I need to mount them to a 35mm camera body somehow. Fixed focus would be ok, but still some kind of spacing would be required.

Hilo · Apr 17, 2016

There must be M39 to M42 adapters. So you could get any M39 (most are !) enlarging lens that has the possibility to go stepless.

After that there are many great (and inexpensive) M42 slr's to chose from

BetterSense · Apr 17, 2016

Yes but even with a thread adapter it will not work because enlarger lenses do not have focus mechanisms and it would be pure luck if they happened to be in focus on the adapter because the lenses are designed to go on something with a bellows.

baachitraka · Apr 17, 2016

You can try Helios 44-2 lens, which have two rings. One to pre-select the aperture and other to open and close it.

BetterSense · Apr 17, 2016

Does the aperture ring turn smoothly and easily, including when the aperture is "closed"?

baachitraka · Apr 17, 2016

There are two rings in 44-2. The one near to front element is aperture pre-selection and the other far from front element rotates freely, eventually closing and opening it.

John Koehrer · Apr 17, 2016

Remove the lens mount and aperture ring. The click ball is under the ring.

Bill Burk · Apr 17, 2016

BetterSense,

Yes a Helios "pre-set" ring turns very freely and is used to open for focusing and close for shooting. You set it at f/16 if you want and then your automatic actuator would meet very little resistance turning over the range of f/stops.

Have fun sounds interesting.

Bill Burk · Apr 17, 2016

John Koehrer said:
Remove the lens mount and aperture ring. The click ball is under the ring.

Are you sure? On an OM the aperture ring is on the front, the lens mount on the back...

monst · Apr 18, 2016

John Koehrer · Apr 18, 2016

Bill Burk said:
Are you sure? On an OM the aperture ring is on the front, the lens mount on the back...

AAARRRGGH. My mind went away for a while.
Thank you Bill.

BetterSense · Apr 19, 2016

monst said:

That looked really easy, but I hit a snag: I don't think the 50/1.8 comes apart that way. I have a G.Zuiko 50/1.4 like in the video, and you can see a couple notches in the threaded ring where a spanner wrench could be used to remove the ring. I was able to get that ring loose pretty easy with a rubber stopper. I also checked my 50/3.5 macro and my 135mm OM lens and they also had the ring with the notches in it, and they also all come loose with the rubber stopper. However, the lens I want to de-click is a very old and ugly 50/1.8 and it does NOT have the notches in the ring and it would not come loose. I don't think the ring is threaded at all since it doesn't have the spanner notches in it. It's still good news though because at least now I know I could buy an ugly 50/1.4 and de-click it pretty easily. I'm still puzzling over how the 50/1.8 actually comes apart now. It's ugly enough I could just disassemble it from the flange end just as a learning exercise.

monst · Apr 21, 2016

you probablty need a rubber bung type thing that just fits the ring with the writing on it, it should screw out with a good bit of grip.

darinwc · Apr 21, 2016

I think the notched ring is recessed around the name plate ring. But that's from memory. I will check tonight.

BetterSense · Apr 21, 2016

I tried the rubber bung. It worked on my 28mm, 135mm and 50/1.4. All those lenses have little notches on the ring with the white writing, like they were designed to fit a spanner wrench, and all of them came loose pretty easily. For some reason the 50/1.8 does not have the notches in the ring which makes me think the ring is not threaded like the other ones. And it doesn't come loose no matter how hard I crank with the rubber stopper.

darinwc · Apr 21, 2016

OK I just tried it. The name plate ring screws right out. There are notches for a spanner receded between the name ring and the filter threads. But it is better to use rubber friction to turn it.

remove detents from OM lens

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