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02-22-2013, 09:53 AM   #1
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To Deglass or Not? PKA macro teleconverter

I recently acquired a Magnicon 3X Macro Auto Teleconverter. There isn't much info out there about teleconverters, except that most should be avoided, especially the 3X ones. There is even less info out there about macro focusing ones of an older era. In fact when I first looked to buy the item, I missed that it was a macro TC.

My interest was that it has A contacts and so I thought about converting it to a single extension tube with A contacts by taking out the glass. It would be a big one, as it is about twice the size of a A50/2 lens. Before I start tinkering too much, I thought I'd just throw this thread to the group and see if anyone had any thoughts/suggestions/advice (which can include trying to sell the thing to someone who knows less that I did as it may be that no good will come from trying to use or modify it).

Some additional questions (this thread started life in another forum, but got no replies so I'm trying it here in extended form)?

Does anyone know if this sort of macro TC was designed primarily or only for 50mm lenses?

Has anyone delgassed a TC and then rebuilt it?

Any thoughts on how best to use this thing? My current choice of A/F lenses include a A50/2, A28/2.8, A35-105/3.5 and F50/1.7 (I'm ignoring anything slower or m42 mount that I have. I'm hoping to pick up a A50/1.7 or 1.4, but not sure when that will happen.

02-22-2013, 10:28 AM   #2
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QuoteOriginally posted by MSL Quote
Has anyone delgassed a TC and then rebuilt it?
Some TCs are very easy to deglass, with no need to disassemble anything; the rings holding the elements simply screw out. In my experience, the ones that aren't easy aren't worth trying. If the ring holding the lens elements has some kind of slot for a lens wrench it is probably the former. If not, probably the latter.

I gather a macro TC has a focusing helicoid? Does the whole thing extend/retract or is the movement internal? In the former case removing the glass would get you an A-type helicoid extension tube, very cool.

I think you're right that these were generally designed for 50mm lenses, at least in that they would get you to 1:1 magnification with a 50.
02-22-2013, 10:31 AM   #3
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QuoteOriginally posted by baro-nite Quote
I gather a macro TC has a focusing helicoid? Does the whole thing extend/retract or is the movement internal? In the former case removing the glass would get you an A-type helicoid extension tube, very cool.
Unfortunately, the former - all the movement is internal.

I didn't mention before, but if the best option is to deglass destructively, I'd certainly consider that option. What little I could find out about 3X converters in general is that they were all 4 element rather than 7, and so of poorer quality. Losing three stops doesn't help much either.
02-22-2013, 10:36 AM   #4
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For an easy conversion look for KAR (Ricoh type) 2x TCs, made under a variety of brands but probably all the same unit. Easiest if you get one that doesn't have anodized (black) mounting plates.

02-22-2013, 10:38 AM   #5
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QuoteOriginally posted by baro-nite Quote
For an easy conversion look for KAR (Ricoh type) 2x TCs, made under a variety of brands but probably all the same unit. Easiest if you get one that doesn't have anodized (black) mounting plates.

Will do. Just spotted a local sale for a Vivitar 2x KA which I might grab.

This particular one is listed as a 3 X Macro Auto Tele Converter Multi-Coated KR - it has the A contacts and if it has the Ricoh pin, it is not an offensive one.
02-22-2013, 10:44 AM   #6
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You are losing 3 stops with this converter so even if it's used with fast 50's you will be shooting in the dark. Anything slower than f2.8 would be more or less unusable with this TC. Still, I think it will be fun to fool around with this TC, never mind the image degradation. I think it was designed to be "Tele" converter but losing 3 stops on a typical telephoto lens of the same era makes these TC impractical. And, what would be the purpose of putting it on a fast 50, just to turn it into a very slow 150 with noticeable image degradation? This TC's contemporary mid telephoto lenses were faster with decent IQ, I don't think there is any practical reason to keep it as a TC.

I would go ahead and turn it into a macro extension tube or if you want the smaller 2x extension instead, please pm me and we can arrange a trade.
02-22-2013, 11:04 AM   #7
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Today's new and used marketplace has a good selection of relatively low-cost prime lenses with very good macro performance; lenses that weren't available a few decades ago when macro converters were popular accessories. Consequently the value and utility of those converters is very low now.

IMO, if you feel you have good use for an AE/AF capable macro extension tube converted from one of the older teleconverters you'd be justified in modifying any but the most highly rated newer units such as the Pz-AF 1.4, AFA 1.7 or the new Kenko or Vivitar items.

I've converted four older, fixed power PK/A capable units (including an Adaptall 2x tube) and find them very convenient and effective. However, I haven't modified a PK/A Vivitar 2x Variable Macro unit as it still has excellent utility with older 35-50mm SMC M- and A-class lenses.

Other than esthetics, I've found no value in modifying older PK tele-converters compared to using conventional extension rings and the TC conversions do weigh significantly more.

H2
02-22-2013, 11:05 AM   #8
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Did you try it out, to see how it actually performs with a fast 50?
You can get extension tube packages pretty cheap on ebay these days, don't see why you would go through the trouble of deglassing. Do the contacts really make such a big difference?

02-22-2013, 11:18 AM   #9
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TC and focusing Macro-TC, in general, do not make good extension tubes or focusing helicoids.

The problem with de-glassing is the lens element mounts block part of the light path, causing vignette.
02-22-2013, 11:37 AM   #10
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QuoteOriginally posted by rhodopsin Quote
The problem with de-glassing is the lens element mounts block part of the light path, causing vignette.
I've never found this to be the case, and I've done quite a lot of shooting with these.
02-22-2013, 11:39 AM   #11
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QuoteOriginally posted by Na Horuk Quote
You can get extension tube packages pretty cheap on ebay these days, don't see why you would go through the trouble of deglassing. Do the contacts really make such a big difference?
They give you a lot more flexibility to focus wide open and then not have to tinker with the green button before shooting. I tend to find I shoot with my m42 extension tubes more than my PK ones because I find I can throw the A/M switch on the lens without disturbing my grip, more so than with the PK tubes and needing to tweak the camera. That said, I also don't use the PK tubes as much because the set I bought had a broken segment and as it was the smallest one, it cut down on the usefulness of the set considerably.




QuoteOriginally posted by rhodopsin Quote
TC and focusing Macro-TC, in general, do not make good extension tubes or focusing helicoids. The problem with de-glassing is the lens element mounts block part of the light path, causing vignette.
I did wonder about that. One reason I'm proceeding slowly, and may just try to sell the item rather than tinker with it.
02-22-2013, 11:40 AM   #12
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QuoteOriginally posted by baro-nite Quote
I've never found this to be the case, and I've done quite a lot of shooting with these.
Also reassuring to hear. Although I've just looked at this TC next to my Vivitar AT-22 tubes and I can see that the optical path will be a lot narrower.

Thanks for the ongoing input as the lack of any response to my original thread was most discouraging.

Last edited by MSL; 02-22-2013 at 01:04 PM.
02-22-2013, 01:00 PM   #13
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QuoteOriginally posted by baro-nite Quote
I've never found this to be the case, and I've done quite a lot of shooting with these.
Likewise, there is no vignetting, just gets darker as more extension is added on.
02-22-2013, 02:12 PM   #14
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QuoteOriginally posted by rhodopsin Quote
The problem with de-glassing is the lens element mounts block part of the light path, causing vignette.
Not so -- not even when used on FF / film body.
02-22-2013, 10:21 PM   #15
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QuoteOriginally posted by MSL Quote
I recently acquired a Magnicon 3X Macro Auto Teleconverter. There isn't much info out there about teleconverters, except that most should be avoided, especially the 3X ones. There is even less info out there about macro focusing ones of an older era. In fact when I first looked to buy the item, I missed that it was a macro TC.

My interest was that it has A contacts and so I thought about converting it to a single extension tube with A contacts by taking out the glass. It would be a big one, as it is about twice the size of a A50/2 lens. Before I start tinkering too much, I thought I'd just throw this thread to the group and see if anyone had any thoughts/suggestions/advice (which can include trying to sell the thing to someone who knows less that I did as it may be that no good will come from trying to use or modify it).

Some additional questions (this thread started life in another forum, but got no replies so I'm trying it here in extended form)?

Does anyone know if this sort of macro TC was designed primarily or only for 50mm lenses?

Has anyone delgassed a TC and then rebuilt it?

Any thoughts on how best to use this thing? My current choice of A/F lenses include a A50/2, A28/2.8, A35-105/3.5 and F50/1.7 (I'm ignoring anything slower or m42 mount that I have. I'm hoping to pick up a A50/1.7 or 1.4, but not sure when that will happen.
I've deglazed the Vivitar 2x Macro Convertor. You can remove some of the lenses before running across ones that have been press fitted from either side. As I have two more of these I smashed the lenses sending glass into the mechanism which I don't recommend. I have a friend with an Ultrasonic Cleaner that should be able to remove any pieces I've missed but I haven't done this yet.

I can say the 2x stunned me when testing as there was no visible image degradation using it.
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