Nikon EL2 - Manual (Page 55)

■ Auto exposure control with stop-down metering
When using a bellows or other extension equipment
which disengages the meter coupling device, it is neces­
sary to revert to stop-down metering. Certain limita­
tions are imposed in this mode.
As lens-to-film distance is increased, the metering range
(EV range) changes proportionately. For example, when
an f/2.0 lens is used at 2:1 reproduction (twice life-size)
the effective f/number is f/5.6 When used at f/8, the
effective f/number is f/22.
When pictures are taken under minimal light levels, it is
desirable to use a high-speed film (ASA 160 or higher).
Using Tri-X at film speed 400 with stop-down metering,
with an effective f/number of f/8, the shutter speed
range would be from 1/4 second to 1/1000. Should the
light level drop below EV 6, it would be out of the
shutter speed range of the meter.
Table Slowest shutter speed at full
aperture with any lens
ASA speed
Slowest shutter speed
(sec.)
3200 1/30
1600 1/15
800 1/8
400 1/4
200 (160) 1/2
100 ( 80) 1
50 ( 64) 2
25 4
12 8
35