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Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 25
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 09, 2006 - 07:06 am: | 
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It's Saturday, toil&torment in the tinkerer's den, and I'm puzzled.
After reading half the internet library on after-market-third-party-zoom-lenses I bought two obviously identical scrappy lenses hoping to get one of them going again, but they turned out to be as different as porcupines and hedgehogs. They are both "Exakta", with a "k", 28-200 mm zooms. My idea to swap the PK bayonet of the lens in better shape and replace it for the MC/MD mount of the junker cannot be put into practice because the sockets are not interchangeable: although the aperture activating pins have the same shape and size and would match, the lenses slightly differ in diamter, number and make-up of screws; one has plastic (grrr!) tubes and frame, whereas there are metal parts on the other.
I learned that names of lenses are meaningless and superficial similarity is an empty promise.
Please help me to unveil the mysteries of the lens conjurers!
Is my basic assumption right that just the sockets of the same batch of a type of lenses are different? How can I be sure to get appropriate spares to turn the better (metal) zoom into a lens to fit MC/MD ? Is another junker off ebay my last chance to finish this project? How can I tell plastic from metal in a photo on the PC screen in order not to pick a lemon again? W. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 26
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 15, 2006 - 04:20 am: |
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After one week's time it is perhaps the right time to ask again: a company producing lenses certainly did not produce as many different types of 28-200mm zoom lenses as there are (or were) camera mounts. That is what makes me think lenses as such, that is bodies and glass elements, are identical and just mounts (bayonets, threads) are different.
Does anybody know if these usually fixed mounts (Pentax, for example) can be removed and then be replaced by one fitting other cameras (say Minolta) ? |
Henry
Moderator
Username: Henry
Post Number: 23
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 15, 2006 - 07:55 am: |
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I can answer about Kino Optics...ie. Kiron lenses. They are definitely exchangeable. I have done it. However, it isn't simply swapping mounts. The internal linkage must also be exchanged.
Henry |
Henry
Moderator
Username: Henry
Post Number: 24
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 15, 2006 - 08:29 am: |
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Opps Werner,
I didn't read your fist post until reading and answering your second post. I thought you were talking about, say, turning a Kiron Pentax mount into an Olympus mount, as I did a couple years ago combining two Kirons. What you are asking about is swapping mounts on dissimilar brand lenses.
I have actually done this kind of lens hacking several times. Mostly I've taken Pentax screw mounts off 3rd party lenses with nasty optics and put then on Exakta mount lenses with great glass. Making very nice (and very cheap) glass for my Spotmatics. The trick is getting the back focus distances the same. Being old Exakta mount lenses there were no aperture pins to fool with. You'll be doing stop down metering on your Minolta also.
You have a list of back focus distances I trust? |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 27
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, September 15, 2006 - 11:13 am: |
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Hi Henry,
your answers are both helpful, and the lenses I am trying to mingle together are just branded "Exakta", this is to say they have got nothing to do with Ihagee or Dresden or anything similar. They are both of Japanese origin, and meanwhile I have seen technically identical but differently branded specimen with all sorts of mounts. I will watch out for a metal-bodied junker with an SR, MC or MD bayonet mount and cannibalize it for the parts needed.
Back focus distance on the one I am going to restore is adjustable, having realized this when inspecting it was what on the one hand made me think that there was one single lens design for many different mounts and on the other hand inspired me to begin the whole operation, W. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 61
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, September 16, 2006 - 03:06 pm: |
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It's possible that the lenses were not made by the same company, or perhaps were from different time periods and so represented different versions of the lens. I think that in most cases, third party lenses were made with as many interchangeable parts as possible to keep costs down, so lenses from the same factory and date should be easy to swap - in a few, the mount (though not intended to be user-interchangeable) actually bayonets off of the lens. However, with a name like "Exakta", they may have shopped around for the best price and bought from more than one maker. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 30
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, September 17, 2006 - 03:18 pm: |
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Thank you Rick, meanwhile I have realized that it is more difficult to find the suitable type of lens for parts, no matter whether it is named "Vivitar", "Exakta" or whatever, than to reassemble those parts to match with a certain type of camera. The optically and mechanically better ones are hard to find.
Another result of my search is that the younger a lens is, the more plastic the makers used; some of the lenses from the nineties are very cheaply made inside and can be considered crap. Obviously these makers didn't care about their reputation and were only interested in selling as much as possible knowing that the (manually operated non-digital) SLR hype was ebbing away. |
Dgillette4
Tinkerer
Username: Dgillette4
Post Number: 1
Registered: 04-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, April 18, 2007 - 11:41 am: |
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Hi Werner: I have adaptded lenses for other cameras but used them as presets, I had to mill the mount to focus, I'm sure there are a lot of tamron adaptall lenses oudt there, they were pretty good optically..Don |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 118
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 19, 2007 - 01:19 am: |
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Hi Dgillette4, have solved that problem in pretty much the same way you suggest, thank you for your input on the matter, W. |
John_shriver
Tinkerer
Username: John_shriver
Post Number: 11
Registered: 12-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 20, 2007 - 06:52 pm: |
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Interchangable mounts for Exacta were made in T-mount (properly T-2), T-4, Tamron Adaptamatic, Tamron Adaptall, and Komura Unidapter. Maybe more than that. Find the interchangeable mount (you may need to buy a lens to get the more unusual ones), and then you can use all the matching lenses.
Oh, Sigma Y-S lenses can be used on Exakta with a T-mount, you will need to add a shim to hold the iris closed. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 205
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, October 16, 2007 - 03:46 am: |
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Meanwhile I have completed this project. I had to learn Exakta does not mean Exakta, or anything else.
The 1980's all-metal "Exakta" 28-200 zoom was marketed under different names, I have seen slightly different looking variants in all sorts of mounts (mainly PK though) and it was most probably made by Cosina (which doesn't mean anything either).
On my specimen it was possible to take off the PK bayonet components and replace them by Minolta SR/MD fitting parts. (Reqiures the removal of a depth-of-field cover ring, losening of six setscrews, chrome or mat black). A possibly gummed-up aperture module is easily accessible: #1: name ring removal, it is only glued on. #2: unscrewing the front lens group - round holes, not the long notches, these are for the front glass! #3: second lens group removal - this time it's the two-notched retainer ring, the round holes are for the front glass of that lens group. # 4: removal of two teflon coated guide screws - aperture module incl. the third lens group comes out as a whole through the front. The last lens group can be unscrewed from behind, and that is it. Further dismantling is only necessary for regreasing the heliciol or the macro facility (at the long end of the range).
Wide end infinity/flange distance adjustment is done by means of a turnable distance ring and the above mentioned six setscrews inside the mount, telefocus adjustment is done by turning the front lens group against a "sandwich" of three wavy spring collars.
I know of even a CZJ licensed version of this lens (saw one with a Canon mount). While this one (3.8/5.6 28-200) is a fine solid state lens of some optical performance, the newer all lightweight plastic version is not only optically different 3.5/5.6 28-200 but also mechanically very flimsily constructed crap. |
Wernerjb
Tinkerer
Username: Wernerjb
Post Number: 206
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, October 18, 2007 - 05:07 am: |
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Addendum: When hacking lenses and merging parts from two sources into one good user one has to be careful not to install inadequate components that do fit but won't work.
On some SLR bodies the aperture ring of the lenses has to be turned to the right for opening and vice versa. On cameras with open diaphragm TTL metering when shooting the fully automatic aperture blades will be activated and then move in the same manner. It is therefore not possible to swap the aperture module between lenses that were designed to fit either MD or PK, for instance. Even if the blades move when taking a picture, they will move in the wrong direction and will, for example, open more when they are supposed to stop down. This means only those shots taken midway, with say f8, are correctly exposed. Despite this testing the aperture function by hand will not so easily reveal what is wrong. In my case a test film helped to unveil that mystery. |
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