Piers Hemy wrote:
>I am still struggling with the concept of different mags with the same
>extension and the same focal
> length, but never mind!
I think the extra 'hidden' extension is built into the later lensheads, perhaps
to improve compatability with the ringflashes and macro shoe ring (i.e mounting
the front element in a 'snout' which protrudes beyond the 'filter' ring. I
write 'filter' 'cos the same snout obviously prevents the fitting of a filter
to the ring - but helps the macro flashes light subjects very close to the
front element)
>Here are the markings for 20mm and 38mm, with the marked extension in mm(which
>matches the
>physical distance between lens flanges):
>70mm = 7x with 20mm lens
>About 81mm = 3.5x with 38mm lens
>90mm = 8x with 20mm lens
>Very nearly 100mm = 4x with 38mm lens
>110mm = 9x with 20mm lens
Yeah, that agrees with the pictures I've just received from another list member
- which means these tubes are definitely marked for the later versions of the
lensheads. The picture in my OM1n brochure is clearly of a different version
(which was probably never marketed?) The most obvious difference is the lack of
a central 'ruler' - in its place the tube is marked for the '80+close-up'
The markings for the 38 mm run:
2.5X - 3X - 3.5X - 4X
and for the 20mm:
5.8X - 7X - 8.3X
Attention collectors!!! - ultra rare! - will no doubt appear on *bay soon
;-)).
Adam
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