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07-07-2011, 12:34 PM   #16
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De nada. Yes, the other methods require replacing the base, so the lens can only be used on the new mount. Contax- Yashica C/Y mount lenses can be modified in exactly the same way, except that the aperture is spring-loaded shut, so there is no need to tape or jam an aperture button or flag. And C/Y lenses so modified can also be used on their original cameras also. Many good OM and C/Y lenses are available, cheap; this is an easy way to expand our collections!


Last edited by RioRico; 08-13-2011 at 08:20 PM.
08-13-2011, 08:04 PM   #17
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This mod looks easy enough. My reason for bumping the thread back up is that today was our town wide garage sale day. I came across couple of Zuiko lenses, a 50/1.8 and a 100-200/5 zoom for $3 for the pair. They appear to be in perfect condition. The lady tossed the camera because the shutter broke. I also snagged a Chinon CS in excellent condition with a 55/1.7 that I immediately tried out on my K10D and the shots looked pretty good. I'll pick up a battery at Radio Shack for the camera's light meter and run a roll of film through it. Along with a few other goodies like a camera bag and a bunch of filters, I spent $10 total. I'll spend more for the Dremel tool as the work looks a little fine for my Snap-On air die grinder.
08-13-2011, 08:26 PM   #18
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Yeah, some Dremel #426 metal-cutting blades (maybe US$12 for a batch of 5) are well worth having for any lens mods. The Zuiko 50/1.8 is common and good and and an easy target. I'm not sure about the zoom. I'm hesitant to put modded lenses weighing over 500g onto a PK mount. But if it's lighter, no problem. Good luck!
08-14-2011, 06:19 AM   #19
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What kind of aperture control do you get with the original olympus mount? Can the camera control the aperture at all? I have 2 that I have converted. One is an f.zuiko 50mm 1.8. It is just pinned wide open (no aperture control) using a m42 adapter. I found that the counter sink that I bent in the adapter with a punch pushed the mount out far enough it gave me just past infinity.

I also just got a vivitar series 1 70-210 3.5 ver 2. The aperture ring works like an adapted m42 lens (turn the ring only, no way to quick stop down and no camera control). Would a modding the olympus mount work better?
I got the vivitar dirt cheap and did an impatient rush job. In the end it came out very good but ugly. The m42 adapter was too big around (at the time I didn't realize that I would have to space it out over .200" because the original adapter was .277" thick). I looked for the first 3 screw k mount I could steal off a lens and wound up sacrificing a very worn but functioning jcpeney 135mm 2.8 (got it for cost of shipping). As luck would have it, it fit perfect. I realized that it needed to be spaced out and got .200" using a 52mm-49mm step ring with groves cut for the screws to clear. That pushed it just past infinity (I could fine tune it by thinning the step ring but may not bother as it is close and does go past infinity). That gave me a solid mount but left nothing holding the aperture ring down (it could slide up and the detente ball would come out). I cut up the plastic liner from a filter case (seemed to fit perfectly over the aperture ring). It was too thick and split. ; realized my design flaw and made another that works perfectly (but is ugly).
I can post pics tonight if anyone wants (right now I'm going to be late for work).

08-14-2011, 09:31 AM   #20
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QuoteOriginally posted by ripit Quote
What kind of aperture control do you get with the original olympus mount? Can the camera control the aperture at all? I have 2 that I have converted. One is an f.zuiko 50mm 1.8. It is just pinned wide open (no aperture control) using a m42 adapter. I found that the counter sink that I bent in the adapter with a punch pushed the mount out far enough it gave me just past infinity.
With my trim-the-bayonet-flags mod, there is no camera-lens aperture linkage, no in-camera control of the aperture. The Olympus base has two opposing buttons, one for lens removal, the other for manual aperture stop-down. I tape-over the latter; but if you want the ability to meter wide-open and then manually stop-down, just leave the button as-is and press it when desired.

QuoteQuote:
I also just got a vivitar series 1 70-210 3.5 ver 2. The aperture ring works like an adapted m42 lens (turn the ring only, no way to quick stop down and no camera control). Would a modding the olympus mount work better?
I would not advise modding the big Vivitar zoom because of its weight. I am very hesitant to hang a modded lens weighing more than 500-600g off the lens mount, and that lens is in the neighborhood of 900g (my Ver.1 is 880g naked).
08-14-2011, 07:06 PM   #21
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Are you talking about being worried about using a modded Olympus mount on a heavy lens or any kind of modded mount? Taking measurements of an olympus mount and a pentax mount they seem to be pretty close and I would think that it would have good engagement. I still think it might make me a little nervous though.
I am in the process of trying to mod a nikon t4 adapter which makes me a lot more nervous (the vivitar 90-230mm that would be used with it is even bigger and heavier than the 70-210mm. Further, the engagement is only half, so in theory, if the lens got pushed all the way to one side, the lug on the other side could just slip out. I have a lens on the way that may have a tx-pk adapter on it so it may be a mute point (too bad I destroyed the nikon adapter, I could have sold it).
On a side note, I thought nikon mounts were supposed to be close and some would fit on tight? The one I am working on is requiring a huge amount of material removal to fit.

The vivitar 70-210 is already modded and I am comfortable it can take the weight. at first I was going to use an m42-pk adapter but thought it would be too big around to fit. Turns out it would need a spacer and the diameter of the adapter wouldn't matter. I would up using a mount off a donor lens. The flange is more than twice as thick as an m42 adapter, and its plated (maybe steel). It looks a lot tougher than a cheap Chinese thin soft aluminum adapter. I use the original screws and while it only had 3, they were about 1/2" long so they have about 1/4" thread engagement inside the lens. The original factory holes lined up perfectly with the new mount (I think the hole spacing was the same on both mounts). The spacer is a metal step ring. I had to add a spacer to hold the aperture ring down which is flimsy plastic, but it has nothing to do with the structure of the mount. It just holds the aperture ring down (ghetto white plastic till I find something better).
Here are pics
https://www.pentaxforums.com/forums/1614787-post150.html
here is an f.zuiko modded with an m42 adapter (I wouldn't trust it with much weight). second pic
https://www.pentaxforums.com/forums/1614767-post149.html
08-18-2011, 01:05 PM   #22
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guys, surely the registration distance for Pentax and Olympus is different...there are some really interesting lenses in the Olympus range

I recently discovered this guys unofficial Zuiko page, it opens up a new dimension of LBA opportunities:
http://www.star.ucl.ac.uk/~rwesson/esif/om-sif/lensgroup/21mmf2.htm

There is a 21mm f2 Olympus lens, which sounds pretty amazing. But when buying a lens for USD1000, I'd have thought its safer to get a matching body to go with it!
08-18-2011, 01:56 PM   #23
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QuoteOriginally posted by hoojammyflip Quote
guys, surely the registration distance for Pentax and Olympus is different...there are some really interesting lenses in the Olympus range

I recently discovered this guys unofficial Zuiko page, it opens up a new dimension of LBA opportunities:
http://www.star.ucl.ac.uk/~rwesson/esif/om-sif/lensgroup/21mmf2.htm

There is a 21mm f2 Olympus lens, which sounds pretty amazing. But when buying a lens for USD1000, I'd have thought its safer to get a matching body to go with it!
I haven't modified an olympus to fit yet (I have completely tore the olympus mount off and installed a pentax mount though). It theory though (assuming my brain is working in the right direction), the olympus mount is about a half a mm too far out (it would need to be mounted 1/2 mm closer to be where it needs to be). The effect is that you loose a bit of macro but you can focus past infinity. Other than loosing a bit of macro focus range, you still get a fully functional lens that will focus to infinity (and just past). I could have that backwards though.
I know if you replace the mount the .5mm isn't hard to deal with. Doing something like a minolta lens where the lens needs to be 2mm closer to the camera or canon that needs to be 3.5mm closer you get into trouble. You have to shorten the mount that much or you loose infinity focus.

08-18-2011, 02:56 PM   #24
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I knew I had picture of it somewhere. Seems I filed off more than I remember.
https://www.pentaxforums.com/forums/pentax-slr-lens-discussion/144255-lens-no...12-oclock.html
If you just want to skip to the pictures go to post 8 and 9.
08-18-2011, 04:21 PM   #25
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QuoteOriginally posted by hoojammyflip Quote
guys, surely the registration distance for Pentax and Olympus is different...
For simple lens mods, here's my table of registers:
44.7 mm - Exakta-Topcon bayonet
45.46mm - Pentax-Praktica, M42
45.5 mm - Petri, Contax-Yashica
46.0 mm - Olympus OM bayonet
46.5 mm - Nikon F-mount
To adapt Exakta lenses, I shave the adapter, not the lens. For Petri bayonets, I pull the old mount and glue-on a generic M42-PK adapter. For C/Y and OM, I taper the bayonet flags so they slide under the PK mount lugs. Nikons need a couple approaches: trim the aperture ring, or shim the base, or do nothing.

In practice with OM and Nikon, the register discrepancy Ain't No Big Thang. As ripit said, you lose a little up close and can focus past infinity. And there's a way to finesse that: with Nikon pre-AI, I put 1mm spacers under the lens base (washers on the retaining screws). I haven't tried that with an OM lens yet, haven't felt the need.

On C/Y and OM and NI lenses, I may cut a slot in the lens base for the PK locking pin to engage, for a more secure fit. And on all these where I've just trimmed the lens base, I don't try to mount a lens weighing over ~600g. If I had replaced the base with a wide-flange M42-PK adapter, with that adapter held down with 3-54 screws, I would have no qualms about mounting a heavier lens. Hasn't happened yet, though.
08-18-2011, 06:12 PM   #26
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@RioRico, do you think that 3 screws (actually in this case 4) would hold it well enough with an m42 adapter screwed on? I am talking removing the old mount and replacing it. my fear is the tiny screw heads ripping through the aluminum. my next lens is about 540 grams but I have heavier ones in line. The m42 adapter would be countersunk like seen here.
https://www.pentaxforums.com/forums/1507474-post8.html
I should be patient and wait a few weeks for the macro tube. I'm not though. I'm being impatient and want to do it tonight. I guess I could do it and upgrade later. It is a waste of money to do it twice but then again the challenge and fun of it counts for something. If it will hold, maybe the macro tube could be tried out on one of the heavier ones.
08-18-2011, 07:17 PM   #27
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QuoteOriginally posted by ripit Quote
@RioRico, do you think that 3 screws (actually in this case 4) would hold it well enough with an m42 adapter screwed on? I am talking removing the old mount and replacing it. my fear is the tiny screw heads ripping through the aluminum.
If you're worried about the strength of the wide flange of an M42-PK adapter, which indeed might be less than 1/3mm thick, then spend a buck more for a wide-flange M39-PK adapter, which is almost 2mm thick. It's quite strong, even with countersunk holes.
08-18-2011, 07:38 PM   #28
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QuoteOriginally posted by RioRico Quote
If you're worried about the strength of the wide flange of an M42-PK adapter, which indeed might be less than 1/3mm thick, then spend a buck more for a wide-flange M39-PK adapter, which is almost 2mm thick. It's quite strong, even with countersunk holes.
Thanks a lot for the info. ; hadn't really thought of trying other mounts. Are they all pretty standard at that thickness or do they very?
08-18-2011, 09:49 PM   #29
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QuoteOriginally posted by ripit Quote
Thanks a lot for the info. ; hadn't really thought of trying other mounts. Are they all pretty standard at that thickness or do they very?
I've just micrometer'd three M42-PK's from very different batches -- one black with smooth perimeter, one black with serrated perimeter, one chromed with smooth perimeter -- and they all look like 0.5mm. My M39-PK's are all from one batch and measure 2mm thick.

Another source of mounts, besides wrecked lenses: mount-reversal adapters. If you can tap the lens body throat to 49-52-55-58mm thread, these just screw right on.
08-19-2011, 10:00 AM   #30
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Those mount reversal adapters look to have promise. As the macro tubes are actually cheaper I'm going to try those first (I only found 1 seller for the reversal ring right now on ebay so I'll keep an eye out for cheap ones or maybe eventually just try one of those).
I got impatient last night and tried an m42 adapter. It didn't go so hot. I measured the head of the screw after the fact and it is .034" while the adapter is .040" so you can see how in some circumstances you cannot just cut it in. I drove the punch through the first time so indexed over a half inch and tried again. I got ones that look like they may barely work. With screws in a teleconverter wont attach but it looks like it just needs a little more. Tightening it down to the lens might help pull it down a little too (need to make a spacer first).
I guess some lenses have small screws/screw heads and some have big (I'm also guessing mine are bigger as the lenses are heavier and bigger).

I'm thinking either just cut it into a thicker mount like macro tubes or some of the adapters you have suggested, or drill a steel plate with an oversize impression of the detente, and grind down a punch to the right shape too rather than using standard square and tapered punches for use with m42 adapters. Maybe I could even give a little heat from a torch (might blow the heat treat if there is any though). Just having a proper die and punch setup might be enough.
I guess I got a little more experimenting to do.
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