On Sun, 10 Oct 1999 12:44:11 -0500, "Chip Stratton" <cstrat@xxxxxxxxx>
wrote:
>Anyone know what in particular makes the 1-8 screen suited to long telephotos
>and astrophotography, as opposed to the 1-4n screen?
>
>They are both matte screens with circles inscribed in the center (larger in the
>1-8). Using a 500/8 mirror lens, I can't detect any real difference between the
>two in terms of focusing ease or viewfinder brightness. There must be some
>reason, though, that Olympus has such a narrow specification for the use of the
>1-8 screen.
>
>Awaiting your hypotheses.....
>
>
>Chip Stratton
>cstrat@xxxxxxxxx
Hi Chip.
I will quote from the Om-bible (The Olympus OM Way):
===================
The 1-4 screen is an all-matt screen without central focusing aid.
This screen has a centre sport of 8mm diameter not backed by the
Fresnel pattern; this circle is clearly visible and can serve for
instance for measuring maginification scales in close up photogrpahy
by observing how much of a ruler or other graduated scale appears
within the limits of this centre circle. The screen is usable with
wide-angle, standard and medium tele lenses if you prefer matt screen
focusing to a microprism or splitimage wedge; it can also be used with
longer tele lenses and for low magnification macrophotogrpahy. Meter
readings on the screen indicate correct exposure settings.
.....
The 1-8 screen looks similar to the 1-4 screen, but the matted surface
is extra fine and the central Fresnel-free circle has a 9mm diameter.
Out-of-focus details appear with a luminous soft-focus effect due to
light scatter by the Fresnel pattern. This screen is specially
designed for astrophotography and for the longer tele lenses, but it
is also fine for the medium long focus lenses and usable even with
standard and wide-angel lenses down to 35mm. It is also suitable for
macrophotography and the fine screen facilitates precise focusing with
the Varmagni finder. Meter readings on the screen indicate correct
exposure settings.
================end quote/
Like so often when consulting this outstanding book, I have added to
my own knowledge when copying the above text...
Frank van Lindert
Utrecht NL.
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