Hello everyone, I've been interested in getting into some alt glass so obviously here's the place to ask questions. I was looking at some rokkor 58 1.2's and noticed varying model designations. Does anybody have any info?
Thanks, Dan.
There are 4 variations with respect to the naming:
Rokkor-PG
Rokkor-X PG
Rokkor
Rokkor-X
"X" denotes export lenses that were marketed in different places than the non-X. It does not denote anything "Xtra". According to Rokkorfiles.com "In line with Minolta’s practice of labeling products differently in different markets, the lenses were labeled “Rokkor-X” in the North American market, and “Rokkor” throughout the rest of the world. It is noted that apart from this minor cosmetic change there is no difference between the Rokkor and Rokkor-X version of the same lens. "
"PG" Denotes the lens formula of 7 elements in 5 groups.
First Letter (no. of groups): T=3; Q=4; P=5; H=6; S=7; O=8; N=9.
Second Letter (no. of elements): C=3; D=4; E=5; F=6; G=7; H=8; I=9; J=10; K=11; L=12.
The practice of including the lens formula was dropped in the third generation of Minolta MC mount lenses. Hence, this third generation would have the label "Rokkor" or "Rokkor-X" depending on what market it was destined for.
The older, all metal versions are all "Rokkor-PG" but there are also some rubber-gripped "Rokkor-PG", and some rubber-gripped "Rokkor-X PG". "Rokkor" and "Rokkor-X" are all rubber-gripped.
They are all multi-coated, right from the 200xxxx series right up to the last ones. I know this for a fact because my 200xxxx and 2 other 200xxxx copies that I have had all had green/blue, pink/purple and yellow coatings. The question is, which surfaces of which elements where multi-coated and how did that change over time? Nobody knows for sure.
The multicoating almost certainly changed over the years, but this is not correlated with serial numbers or body style as far as I can tell. Take any one of them and tilt it in the light and you'll see various colours. However, it is believed that coatings on the MC 2nd and 3rd generation lenses are generally better than those on the earlier 1st generation lenses. This is only a generalization because the coatings were undergoing continual development during this period, and accordingly the break from “old” coatings to “new” coatings was progressive, and it is actually likely that there were multiple improvements throughout this period.
One other notable difference is the presence of thorium (radioactive) glass in the first few runs. Lenses with serial numbers 200xxxx, 250xxxx, 255xxxx, and at least some of the 256xxxx have this. Lenses from 257xxxx through 27xxxxx series do not.
They are all excellent lenses (although there certainly is some sample variation after all this time), but the one I kept over many others is a 200xxxx Rokkor-PG.
The conversion process to EF mount is identical for all of them.
If you haven't been there - start with The Rokkor Files - rokkorfiles - for some nice gee whizz info - it's a good site. The Pros here will soon provide more than enough on this outstanding lens. I'm using one on a 5D without a modified mirror and just slightly, slightly under true infinity with a JB adapter and shaved lens rear housing.
they probably used lanthanum glass rather than thorium glass (which was abandoned/replaced long before Rokkors were built, generally) but the effect (reversible yellowing) is similar.
I am pretty sure that the 55/1.2 Zuiko lenses up to about sn 135,000 (with chrome front ring) have thorium containing elements. From about mid 1977, those with a black front ring, don't show any radioactivity. To my knowledge, it were the big optical glass manufacturers (Schott, Hoya), which have not used Thorium (but still Lanthanum, which is much less radioactive) in their production anymore from the mid 1970th, which forced the lens manufacturers to reformulate their lens designs (at least slightly).
From this timing, I expect that the early 58/1.2 Rokkor's have thorium containing glass, which causes the yellowing.
The following links (arbitrary selection) might be of interest:
cogitech wrote:
First Letter (no. of groups): T=3; Q=4; P=5; H=6; S=7; O=8; N=9.
Second Letter (no. of elements): C=3; D=4; E=5; F=6; G=7; H=8; I=9; J=10; K=11; L=12.
So this means the Rokkor TC has 3 lenses in 3 groups? Why does that not make any sense?
Yes, the early 1960's Rokkor TC's 135/4 and 100/4 had 3 elements, none of them glued together, which means each element represents one group. Makes sense to me.
As Laminin says, yes it makes sense. As another example, my current choice of 135mm lens has only 4 elements in 4 groups. The classic "Tessar" design is 4 elements in 3 groups, etc.
Laminin - thanks for the info. I had thought thorium glass discontinued back in the 50s-60s but maybe I am wrong on that. Lanthanum was used as the replacement, yes (though it too is probably discontinued now). the early rokkors did yellow. I have one of them (20016xx), but the good news is they can be cleared with UV. Optically I am not sure if the earlier ones are better - haven't done an exhaustive test on my 2 yet. (one early, one late) Modern Photography liked the later one better that they tested but that could be sample variation also. It was about the best 50ish 1.2 (wide open) they ever tested, fwiw. I'll post the tests soon.
Tessar and other small-element-count lenses can do quite well. they do have their limitations but within them they are surprisingly good.
Laminin wrote:
Yes, the early 1960's Rokkor TC's 135/4 and 100/4 had 3 elements, none of them glued together, which means each element represents one group. Makes sense to me.
Sorry... mental hang-up for me. I know it makes sense, but the idea of grouping things that are not grouped, doesn't make logical sense, semantically speaking.
Nevermind me... my brain is slowly turning to mush.
