Aetna Rokunar 300mm f5.6

[Scheimpflug]

Just picked this one up today, an Aetna Rokunar 300mm f5.6. It came to me with an inoperable aperture, a loose barrel, and no set screw in the tripod collar. But for once, the right mount!!

I've already fixed the aperture (a stuck stop-down mechanism), as well as the barrel (three loose set screws behind the tripod collar, accessible through the tripod socket).


I don't know anything about this lens, so I'll describe it. It has a built-in sliding lens hood that is quite large:


.. and it extends a considerable length when you focus it.




The close focus is quite close, somewhere in the range of 1 to 1.5m. It gives dim blueish reflections off of the front element, so I believe it is multi-coated, and it was made in Japan. The Nikon mount is permanent, and is not a T-mount.



With the lens and hood collapsed, it is the same length as my 30cm (300mm) Minolta TELE ROKKOR-QD, f/5.6, but the Minolta is narrower and noticeably lighter. The Aetna appears to have better coatings than the Minolta, and focuses much closer (1.5m vs 4.5m). The Minolta is a preset lens, while this Aetna is *not* a preset.


Other than that, I don't know anything, and the search is turning up results for much older Aetna lenses. Does anyone know anything about this particular model, or Aetna in general during this time period?

Thanks.

[luisalegria]

Aetna was a brand name used by a US importer that at one time also used other well-known trademarks either by themselves or in conjunction with Aetna - "Rokunar", "Coligon", etc.

Just about everything was sold under this brand/brands, so there is no way at all to tell what you have without a picture.

[ManualFocus-G]

That's a carbon copy of the Tamron Adaptamatic 300/5.6 and some of the earlier Adaptall 300/5.6 designs. So it's a Tamron basically!

[Scheimpflug]

[Scheimpflug]

[ManualFocus-G]

Several people here have seen good results with theirs, although my example was pretty crappy to be honest!

[luisalegria]

No, I didn't see your pictures, I don't know why. Perhaps my work internet settings are interfering. I do see Scheimpflugs pictures though.

I also have this Tamron. I find it excellent, its my favorite 300mm at the moment.

[mo]

Nice buy Scheimp! I have a 135 adaptamatic. You know pictures from this lens are expected!

[Scheimpflug]

[Scheimpflug]

[Scheimpflug]

[revers]

Nice surprise.

I am afraid it would be just too heavy on my G1, in fact the Vivitar Series 1 70-210/3.5 is.

[Scheimpflug]

[eccs19]

I've also got the Tamron version of this lens. Admittedly I was never really happy with it. I've not yet tried it on my K7. Maybe I'll have to give it another go. I did find it has really bad PF wide open, and I just didn't find it that sharp. Maybe I'll have better results on K7.

[revers]

"You have the v2 Tokina version of that lens, right? "

That is correct.

After seeing your shots it this thread I went out this morning & tried something similar. See my post Sears 80-200/4.0.

[Scheimpflug]

[ManualFocus-G]

[Scheimpflug]

[Scheimpflug]

I'm starting to think that perhaps this lens is NOT a direct copy of the Adaptamatic Auto Tamron... or any of the Tamron 300mm f5.6's for that matter. I've been comparing the versions, and mine just doesn't match up.


So here's mine, the Aetna Rokunar 300mm f5.6:



.. and now let's look at the Tamrons. First is the Auto Tamron, with the Adaptamatic mount, model 670Au:

http://www.adaptall-2.com/lenses/670Au.html
(edit: now http://www.adaptall-2.org/lenses/670Au.html)


followed by the early (transitional?) Adaptall version (posted on the forum here by member dab63, but not listed on adaptall-2.com):

http://forum.mflenses.com/silver-tamron-300mm-f-5-6-adapt-a-matic-or-adaptall-t23757.html


followed by the Adaptall version, model CT-300:

http://www.tamron.co.jp/data/old-lens/ct300.htm


followed by the Adaptall-2 SP version, model 54B:

http://www.adaptall-2.com/lenses/54B.html
(edit: now http://www.adaptall-2.org/lenses/54B.html)



Comparisons:

• The Aetna has the most visual similarity to the Auto Tamron.
  
• The presence of a tripod collar on the Aetna matches it with the Auto Tamron and the early Adaptall.
  
• The Aetna's focus/DOF "tree" is a diagonal fan-out style, matching the Adaptall version of the Tamron, but not the Auto Tamron or the early Adaptall.
  
• The Aetna has 62mm filter threads match the Auto Tamron and the early Adaptall, but not the Adaptall or Adaptall-2 SP models (58mm).
  
• The Aetna's focus grip moves away from the mount when focusing, which matches everything except the Adaptall-2 SP.
  
• The Aetna's close focus distance is around 1.5m, and the lowest marking on the focus ring is 1.7m. The minimum focus for the Auto Tamron is 2.5m, and remains 2.5m for the Adaptall version. The only Tamron with a closer close focus is the Adaptall-2 SP at 1.4m.
  
• The only Tamron to get consistent good reviews for optical quality is the Adaptall-2 SP.
  
• The Adaptamatic has 4 elements in 2 groups, the Adaptall has 4 elements in 4 groups, and the Adaptall-2 SP has 6 elements in 5 groups. Looking into my Aetna through the mount side under a bright light with the lens cap on the front, I can see 5 reflections and a possible tiny tiny sixth.

... So what do I have? Is this perhaps not a standard Tamron lens, but maybe a "clean-up" batch to make use of parts left over from other lens designs?

[ManualFocus-G]

Interesting. Please note though, there were at least two versions of the Auto Tamron (Adaptamatic). Mine looked very similar to yours with the same focusing barrel.

[luisalegria]

That Aetna looks like the Adaptamatic version indeed, and I would be surprised if it had a different optical layout, all the other important bits like the focusing helical and aperture mechanism are in exactly the same places as with the Adaptamatic. This all would be different with different glass. The differences vs the Adaptamatic are purely cosmetic. The Adaptall-style DOF scale is a case in point.

I bet this lens was yet another transitional type dating from the early 1970's, when the Adaptalls were coming in, made up possibly from existing bits but certainly from existing Adaptamatic tooling.

There were many undocumented variants it seems, especially those fixed mount types made for third parties. I even have lenses labelled by Taisei (Tamron) that have absolutely no relation to the "known" types.

As for performance - I have absolutely no complaints against my Adaptamatic, its one of those lenses that manages to almost focus itself.

[Scheimpflug]

Luis - what do you think about the large difference in the minimum focus distance? That is pretty much the only piece I can't explain as a cosmetic change...

[luisalegria]

I can't explain it either. I can only speculate. Possibly the helical in the basic Adaptamatic design of this lens has some additional travel available that is limited by a stop - not an unusual situation. For whatever reason - competitive feature bid against a rival maker ? - this one made for Aetna was given closer focus capability, maybe as simply as moving the stop and permitting some more rotation on the helical.

Whatever the explanation, the sum of all the features says "Tamron Adaptamatic" to me.

[visualopsins]

My copy, M42.

[Scheimpflug]

Thanks, visualopsins! That makes two... up until now, I had only know of mine, and I hadn't seen any like it on ebay or anywhere else.

There are some slight differences, such as the chrome trim around the grip on mine, and the fact that mine says "AETNA ROKUNAR" while yours says "AUTO ROKUNAR"... but otherwise they appear to be identical! And now, I know what kind of knob to look for for the tripod collar set-screw.

It is interesting how different the serial numbers are... 296xxx vs 693xxx.