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 From the very beginning of Minolta's SLR
lenses, you could see a two letter code after
the lens designation, for example Auto Tele
Rokkor-PF 1:2.0 f=100mm. This was a code
designating the optical design of the lens.
Lenses are put together by carefully selected
optical glass, finely grinded and polished to a
mathematically selected form and these
optical lens elements can either be
freestanding (with no contact with other lens elements) or grouped
together. The glass elements that are grouped in contact with each
other are cemented together by a special glass bonding material, a
sort of glass cement, at high temperatures.
Minolta choose to engrave the optical design by a
code system. To take a look at the chart of the
design of the above mentioned lens to the right:
The Auto Rokkor-PF lens had five groups of glass
elements with six glass elements in total. Two of
these glasses was cemented together.
The code is composed by two letters; the first
letter designating the number of groups, and the second the
number of glass elements in the lens.
Here is the complete code for translating the designation of lenses.
Top row is the first letter and below is corresponding number of
groups, third row is the code for number of lens element.
T |
Q |
P |
H |
S |
O |
N |
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3 |
4 |
5 |
6 |
7 |
8 |
9 |
10 |
11 |
12 |
C |
D |
E |
F |
G |
H |
I |
J |
K |
L |
From this table it is simple to deduce that a MC W.Rokkor-SI lens
has 9 lens elements, arranged in 7 groups.
Although there is no official explanation, it is easy to see the greek
alphabet in the first code letter designating groups, Penta, Hexa,
Septa, Okta, etc. The second letter is probably just chosen by
alphabetical order.
This numbering continued from the Auto Rokkor and Rokkor lenses
over the MC Rokkor to the MC Rokkor-X lenses until middle or end
of the seventies. Starting with the second generation of the MC
Rokkor-X lenses in 1975, those lenses that had been redesigned
had dropped the code lettering. With the start of the MD Rokkor
lens series, all code letters had disappeared.
The large lens group to the far right are two lens elements cemented together. The thin
visible line on the side separates the two elements. Front lens group taken from MC
Minolta Celtic 1:2.8 f=135mm (second group from front).
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