On: Tue, 11 May 1999 20:59:15
Dan Lau <dlau@xxxxxxxxxxxxxxxx> wrote:
This brought up a question that I've always wanted to know about
teleconverters. I use an OM-1(n) camera, do the teleconverters
automatically account for the shift in aperture in transmitting
the information to the OM-1(n) body? In other words, when a
teleconverter is mounted, should I continue to use the "center
the needle and shoot" method or must I do some mental compensation
for the loss of light (i.e., center the needle first, then open
it up two-stops for the 2X and so on). Thanks.
-Dan
---------------------------------------------------------
If your camera did not have TTL metering you would have to do exactly
the sorts of mental gymnastics you describe. For a 2X converter you
would have to increase the exposure by 2 stops from whatever was
indicated on the lens aperture ring.
Due to the wonders of TTL metering though you don't have to do any of
that. The teleconverter doesn't pass any information to the camera
since the camera doesn't need to know anything about the lens aperture.
It measures the light it sees and combines that with film speed to give
a recommended shutter speed. It doesn't care if the light was a bright
light coming through a small hole or a dimmer light coming through a
large hole.
The TTL metering is also what allows you to use macro or microscope
setups without doing even more complicated exposure calculations.
Except for situations like backlighting that can fool the meter it
doesn't matter what is attached to the camera as a lens. Just center
the meter needle.
Chuck Norcutt
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