At 23:00 6/10/00 , Robert wrote:
>
>There are some design oddities. The 21/3.5 has a 92° angle of view, but still
>takes 49 mm filters. The 24/2.8 and the 24/2 have an 84° angle of view, but
>the former takes 49 mm and the latter takes 55 mm filters. The 28/2 and the
>28/3.5 have a 75° angle of view and both take 49 mm filters. The 35/2 and the
>35/2.8 have the same 63° angle of view, but the former takes 55 mm and the
>latter takes 49 mm filters. Go figure. It has to be a simple matter of lens
>design.
[snip]
I've noted the general correlation between lens speed and filter size also
with the the anomalous 28mm f/2 you mention. There is another, lesser
anomaly among the standards. The newer 50/1.2 has a 49mm ring while the
older 55/1.2 has a 55mm ring. My guess is there is a partial secondary
correlation with when the faster lenses were designed. I believe the 24/2
and 35/2 have been around longer than the 28/2 has.
Of related interest I dredged out a lens brochure circa 1980 that came with
the OM-10 I bought:
Brochure C65E-380D:
(can anyone decode this for date of printing?)
(see notes about the "MC" designation at the end)
----------------------------------
Type Lens MC? *
----------------------------------
Fisheye 8mm f/2.8
16mm f/3.5
----------------------------------
Super Wide 18mm f/3.5 Y
Angle 21mm f/2 Y
21mm f/3.5
24mm f/2 Y
24mm f/2.8
----------------------------------
Wide Angle 28mm f/2 Y
28mm f/3.5
35mm f/2 Y
35mm f/2.8
35mm f/2.8 Shift
----------------------------------
Standard 55mm f/1.2
50mm f/1.4 Y
50mm f/1.8
50mm f/3.5 Macro Y
----------------------------------
Zoom 35- 70mm f/3.6 Y
75-150mm f/4
85-250mm f/5 Y
----------------------------------
Telephoto 85mm f/2 Y
100mm f/2.8
135mm f/2.8 Y
135mm f/3.5
180mm f/2.8 Y
200mm f/4 Y
200mm f/5
----------------------------------
Super 300mm f/4.5
Telephoto 400mm f/6.3 Y
600mm f/6.5 Y
1000mm f/11 Y
----------------------------------
Bellows 20mm f/3.5 Y
Macro 38mm f/3.5 Y
80mm f/4 Y
----------------------------------
* Most of the faster lenses listed above eventually became MC lenses. If
your lens is an "MC" and it doesn't show a "Y" in the table, it's because
it wasn't an "MC" in 1980 and you have a later version of the lens. If
your lens isn't an "MC" but the table shows a "Y" for it, then you have an
earlier version of the lens.
Notably missing in 1980 leading me to conclude they are newer designs:
24mm f/3.5 Shift
28mm f/2.8
28-48 f/4 Zoom
35-70 f/4, f/3.5~4.5, and f/3.5~4.8 Zooms
35-80 f/2.8
35-105 f/3.5~4.5 Zoom
All zooms with a long end above 150mm
40mm f/2
50mm f/1.2
50mm f/2 Macro
90mm f/2 Macro
100mm f/2
135mm f/4.5 Bellows Macro
All of the faster Bellows Macro lenses
All the super-speed, super telephoto lenses
No mention is made of the 2X-A or 1.4X-A Teleconverters.
Extension tubes may have existed then but are not in the brochure.
-- John
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