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03-31-2009, 10:08 PM   #1
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Old F@rt Syndrom (lens mod)

I just gotta share this one - the older folks will understand.

I have a like-new Sears/Minolta 50/1.8 macro and a Tamron Adaptall ring for a P/K-RI mount that I acquired with some other stuff. Seemed like a good rainy day project to perform a "sex-change operation" and build a Pentax-mount macro lens.

Disassembled the lens. Fabricated a linkage to convert the Minolta auto aperture function to an M42 manual equivalent. Lathe turned the fairly robust barrel/spacer to the right length to achieve focus to infinity (I usually don't bother if it's intended as a close-focus project but everything was just going so 'right' for a change).

Turned the Adaptall ring to the perfect dimensions for a concentric fit. Tested the combination for fit and focus and discovered I needed to take just a few thousands more off the front face to set the perfect focal range.

Two an' a half hours of work and ready for final assembly and . . . I discovered in my mindless zen-like state I'd just turned the Pentax bayonet ring off the 'good' side of the adapter!

Ahhh, but those l'il brass curly-cues were coming off the tip of the parting tool so 'purdy'. Instead of facing off a few thousands of an inch I'd removed almost a 1/4 inch of heavy brass and never paid a thought to the fact that what I was doin' was completely bass-ackwards.

Damn, now I've got to scrounge up another P/K-RI adapter ring or cannibalize a defunct lens before I forget where I put all those l'il bitty screws.

H2

04-01-2009, 01:13 AM   #2
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Note to self: don't send any repair work to pacerr...
04-01-2009, 06:40 AM   #3
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Any photos of the lens surgery / post-mortem?
04-01-2009, 02:53 PM   #4
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QuoteOriginally posted by pacerr Quote
I just gotta share this one - the older folks will understand.

I have a like-new Sears/Minolta 50/1.8 macro and a Tamron Adaptall ring for a P/K-RI mount that I acquired with some other stuff. Seemed like a good rainy day project to perform a "sex-change operation" and build a Pentax-mount macro lens.

Disassembled the lens. Fabricated a linkage to convert the Minolta auto aperture function to an M42 manual equivalent. Lathe turned the fairly robust barrel/spacer to the right length to achieve focus to infinity (I usually don't bother if it's intended as a close-focus project but everything was just going so 'right' for a change).

Turned the Adaptall ring to the perfect dimensions for a concentric fit. Tested the combination for fit and focus and discovered I needed to take just a few thousands more off the front face to set the perfect focal range.

Two an' a half hours of work and ready for final assembly and . . . I discovered in my mindless zen-like state I'd just turned the Pentax bayonet ring off the 'good' side of the adapter!

Ahhh, but those l'il brass curly-cues were coming off the tip of the parting tool so 'purdy'. Instead of facing off a few thousands of an inch I'd removed almost a 1/4 inch of heavy brass and never paid a thought to the fact that what I was doin' was completely bass-ackwards.

Damn, now I've got to scrounge up another P/K-RI adapter ring or cannibalize a defunct lens before I forget where I put all those l'il bitty screws.

H2
Sounds like something I would do.

04-01-2009, 05:58 PM   #5
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QuoteOriginally posted by emr Quote
Any photos of the lens surgery / post-mortem?
I haven't posted photos of such projects 'cause there's some things that shouldn't be attempted without adult supervision (as my own projects sometimes prove) but if someone's seriously interested I'd provide descriptions and photos of a few things that have turned out well.

At the moment, I'm also workin' on a *my-pod* and converting a bellows focus rack into a simple pano-correction platform.

'OregonJim' has the right perspective - I make myself sign a 'hold harmless' agreement before all projects that require so much as a cleaning swab these days.

H2

edit: Added pix of pano-head below

Last edited by pacerr; 04-03-2009 at 12:38 PM.
04-01-2009, 06:17 PM   #6
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QuoteOriginally posted by pacerr Quote
At the moment, I'm also workin' on a *my-pod* and converting a bellows focus rack into a simple pano-correction platform.
H2
I like the bellows-rack-to-pano-platform idea. I was thinking of making a pano platform out of various bits of wood, but now you've got me rethinking it. Maybe I'll pick up one of those cheap Chinese bellows I see on eBay all the time...
04-02-2009, 06:33 AM   #7
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Focus racks

QuoteOriginally posted by OregonJim Quote
Maybe I'll pick up one of those cheap Chinese bellows I see on eBay all the time...
Look for one of the discontinued, major brand labels instead. There's some good deals on top of the line slide copier/bellows sets for discontinued mounts. This particular set even came like new with a nice 50mm Minolta lens for $18 two years ago. (How many people are going to wear out a slide copier/bellows unit anyway?!)

Remember, all you need is the focusing rack, not the bellows (although I've grafted bellows lens mounts with no problem). A robust aluminum angle bracket will eventually provide portrait-orientation but at the moment landscape format is adequate. Just experiment with the rack adjustment and mark or record the proper offset for each focal length. Old Vivitar 28/2.5 and SMC 50/1.7 primes keeps things simple for me.

Years ago I simply epoxied a lens to a bellows unit for a quick-fix lab setup rather than mess with the mount.
04-02-2009, 02:53 PM   #8
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"Measure twice, cut once"

But who the hell am I to dish out advice?

( Been there, knackered that up as well )

04-02-2009, 11:27 PM   #9
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04-03-2009, 06:58 AM   #10
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QuoteOriginally posted by pacerr Quote
At the moment, I'm also workin' on a *my-pod* and converting a bellows focus rack into a simple pano-correction platform.
Sorry if I'm a bit dense - maybe it's insufficient (sleep+coffee+imagination) - but what's a "pano-correction platform" and what do simple vs complex ones look like?

[/me nukes cup of water, spoons in powdered caffeine crap + cocoa, hopes...]
04-03-2009, 07:00 AM   #11
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QuoteOriginally posted by RioRico Quote
Sorry if I'm a bit dense - maybe it's insufficient (sleep+coffee+imagination) - but what's a "pano-correction platform" and what do simple vs complex ones look like?

[/me nukes cup of water, spoons in powdered caffeine crap + cocoa, hopes...]
It goes between tripod & camera to allow you rotate about the center of the lens. Makes for more accurate panoramas.
04-03-2009, 11:43 AM   #12
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Pano-head project

OK, here's the more-or-less finished project: uses the focusing rack from a Minolta slide-copier/bellows unit (acquired cheap on ebayy) and a fabricated bracket to accommodate vertical format.

The camera can be continuously adjusted forward or backward to set the pivot point for most any lens when used for panoramic sets. Of course it also serves as a focus rack for macro shots. A stiff cardboard strip with rack settings for each lens as determined by experiment serves to set the adjustment for panos.

About $20 total invested. Plus ONLY a coupl'a hours fabricating the vertical bracket - the measure many, cut once worked for a change on this one.
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04-03-2009, 04:54 PM   #13
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QuoteOriginally posted by RioRico Quote
...what's a "pano-correction platform"...?
QuoteOriginally posted by OregonJim Quote
It goes between tripod & camera to allow you rotate about the center of the lens. Makes for more accurate panoramas.
Ah, right. Now I remember. I use a slotted flat flash bracket for that.

[/me slaps forehead, jars eyeballs loose, wonders where brain has gone]
04-03-2009, 08:18 PM   #14
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QuoteOriginally posted by pacerr Quote
OK, here's the more-or-less finished project: uses the focusing rack from a Minolta slide-copier/bellows unit (acquired cheap on ebayy) and a fabricated bracket to accommodate vertical format.

The camera can be continuously adjusted forward or backward to set the pivot point for most any lens when used for panoramic sets. Of course it also serves as a focus rack for macro shots. A stiff cardboard strip with rack settings for each lens as determined by experiment serves to set the adjustment for panos.

About $20 total invested. Plus ONLY a coupl'a hours fabricating the vertical bracket - the measure many, cut once worked for a change on this one.
I like it! Thanks for the picture! Looks like something even I could handle...
04-03-2009, 10:38 PM   #15
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OJ - No doubt - just don' let me catch ya biddin' against me on the cheap macro racks on ecbay in the future! (Damn, now I've let the cat out 'a the bag.)

(...there's supposed to be a winkie-face here! I just don't use 'em. )

H2
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