佳能FD镜头也没有必要为“锁定”环上的M4 / 3适配器
Jiānéng FD jìngtóu yě méiyǒu bìyào wèi “suǒdìng” huán shàng de M4/ 3 shì pèiqì

:-)

In some cases there is not much to do. For instance if you want to create a shift lens, than on the wide side the best you can use is the Sigma 12-24. That works, but on MFT it's equivalent to ca. 24-50 and sometimes you want wider than that. In that field there is nothing anymore what has aperture ring. The closest you can get is to use a "G" lens with adapter on EOS <--> MFT shift adapter. That would be satisfactory... would be such adapter made with brains. Unfortunately it was made by people who never tried how it works.

@LPowell: I do not understand, why you did use lock ring on FD... FD lens have nice aperture ring don't they?
I did see adapters with extra iris and own aperture ring for EF / EOS (not FD). I wouldn't use any because the iris is not where it was designed, it's a poor man's solution. Proper would be to have an MFT <--> EOS adapter with electronic data transmission for the aperture control. Depending on the transfer protocoll which I am absolutely not familiar with - it could be just not worth to do or maybe not even possible in a small package. So we probably stuck with manual aperture control the way it is in these lock rings.

@LPowell
I have no problems with my fotga adapter. In lock position on the adapter the aperture works normally. In open position it remains wide open. It's easy to see if the aperture is fully functional or not.

Do not have the 1.2 Zuiko, all I did hear the Canon 1.2 SSC is better. In general, the Canon-s seem to generate a lot of praise. The Fujinon 1.2 is probably also good, just it's rare and very-very difficult to get outside of the German area. You probably can pick up at any German flea market it easily - or you need to convince the German eBay seller to send you that lens. There is a lot of confusion because both Fuji and Cosina/Tomioka are marketed usually as "Porst". One is in AX mount, the other in M42 or K. One is 50mm, the other is 55mm. I believe, Fuji is (much) better and (at this moment) much cheaper, too - but let's see. The pictures of the Tokina (see above) were made by Fuji, at 1:16 stop. The pictures of the Fuji

http://www.personal-view.com/talks/discussion/1600/50mm-11.2-fujinon-lens-ax-fujica-mount-on-panny-gh1...-its-possible.#Item_1

were made by micro-Nikkor.... 50mm macro. I did not care much about light, just put the camera next to the keyboard and the light is lousy. Under such conditions Fuji seem to be a better lens.... OK, you do not buy the 1:1.2 for the macro work but you are the judge.

Like my old radioactive Rokkor MC 58 1.2 nice bokeh and built like a tank.

I did gather several 1:1.2 lens and the Cosina / Tomioka / whatever is among them, in "Porst" alias. I did look briefly and it seem to be the worst but not sure yet. Other 1.2 lens I have

Canon FL
Canon SSC
Nikon 55mm
Porst Color Reflex (Fujinon) 50mm
the already mentioned Porst 55 mm made by Cosina

At one occasion (soon) will test them against each other.

@kazuo: I am VERY-VERY sceptic about Tomioka because it is a hype started by two German guys few years ago, they had some Tomioka lens to upload on the eBay and generated a bit of sales pitch. Now it grew into a cult - without respect to the fact, the original M42 Tomioka is merely GEOMETRICALLY a 1:1.2 lens. In order to fit into M42 the rear element was cut, making it probably 1:1.4 or even less. So it's most likely a 1:1.4 (or so) lens from the point of view of light throughput but 1:1.2 geometrically (more difficult to focus properly).

This is my guess only so far, want to test a specimen to verify.

Also to consider:

- in the lens test made in Germany somewhere in 80-s the Yashica ML 1.2 wasn't very exiting (that's the successor of Tomioka) - the Canon SSC and Canon FD was quite better.
- it looks for me, that not the tail did wiggle the dog, but the other way. I.e. the Tomioka 1.2 design may came from Cosina originally to Yashica/Tomioka, not the other way. The later Cosina lens still used that design for a while... while Yashica / Contax at one point rather preferred the German way.

The Cosina lens later were mostly sold in German market as Revue or Porst. Porst seem to be later (has "1:22") but that does not mean, it would be better. Or maybe my specimen is lousy or maybe I was not precise enough while testing. After receiving most of my lens, they go for CLA here. It's cheap (ca. $15 - $30) but takes a while, I completely over-loaded the poor repair guy. Once these went through the CLA will tell more...

I'm a fanboy of the Pentax SMC 1.4. Very nice cinema lens. And real inexpensive.

Nobody mentioned the Revuenon 55mm f1.2, also known by many other names (Porst, Cosina, Rikonon but they all point back to the legendary Tomioka @ M42 mount.)

I just acquired the lens and been shooting with it. I like it very much, its has its own swirly character, especially the bokeh, which is actually very much in the vein of the Nokton f0.95 wide open (think lemon shaped points of light).

Interestingly, if you trace the history of the Revuenon, you will find it was at one point manufactured by Cosina (maybe still is, am not sure). Incidentally, the Revuenon has the same lens elements and build as the Cosina 55mm f1,2, and many people argue they are the same lenses.

Fantastic lens, makes a great pair with the Nokton 0.95

The 50mm 1.2 Nikkor is a great lens for center sharpness.

Also try the Rokkor "X" "MD" late model (orange letters, 49mm filter) 50mm f/1.4. I have quite a few Rokkors and this is my sharpest Rokkor in that range. Some of the models are substantially more resistant to age, and so test netter, Even so, you will see big variations in older lenses. Also look at the 50mm macro.