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Re: [Rollei] Rolleiphot - Iris diaphram
- Subject: Re: [Rollei] Rolleiphot - Iris diaphram
- From: todd <todd_belcher >
- Date: Fri, 09 Nov 2001 17:46:26 +0100
- References: <200111090858.fA98wGA12149 >
Using mirrors, light coming through the viewing lens was compared to light
that was falling on a mirror on the front of the Rolleiphot. This
difference in light was translated into a small movement of a bimetallic
strip that bent a lever to show the amount of light falling. There was a
mechanical linkage that automatically changed the shutter dial when the
iris diaphragm was turned to the f-stops as listed on the table on the
Rolleiflex back. Different film speeds could be set on the Rolleiphot outer
rim which had a dial set ring to compensate for different ISO film in the
linkage...... okay, I'm lying.
All you were supposed to do was stop down the iris diaphragm until you
could no longer see detail in the darkest shadows. Then you were supposed
to read off the shutter / f-stop combination from numbers around the rim of
the Rolleiphot. Viola! Exposure determination.
Rich Lahrson wrote:
> Hi Todd!
> How was this used to set exposures?
> > You can always get one of those old Rolleiphots made from about 1933 to
> > 1941. Originally used for determining exposure, it fits over the viewing
> > lens via bayonet and has an iris that can be closed down thus offering
> > depth of field preview. Being an early accessory, it fits only to bay one.
> > todd