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A bit about ..
Setting Shutter
Speeds
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The electronic cameras, C and LX, do not have
intermediate shutter speeds. Only the values on the
dial are implemented. If the dial is set between
two marked times, the shutter operates at the
nearest adjacent speed.
The A (II, III, & IIIs), B, BL, AX provide
approximate intermediate speeds. The cam that is
attached to the shutter speed dial moves the entire
timing mechanism thereby altering the resistance on
a segmented gear which controls the speed of the
lever with the pins that release the shutter
blades. The cam provides a somewhat linear
resistance movement which provides the approximate
intermediate speeds.
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Remember, on the the speed
selection dial, distances
do NOT represent a linear
increase in shutter speed, so
when setting the dial half-way
between two speeds, the resulting
speed will be slightly slower
than one might expect.
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Actually the spot half-way
(50% of the way) between two
values on the dial produces a
speed increase of only 41%, not
50%, the setting shown will
provide a shutter speed of 1/71
second, rather than 1/75.
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To get a shutter speed of 1/75
second, you must rotate the dial
so that the index mark (black
dot) is slightly closer to the
100, nearly 60% of the way from
50 to 100.
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This may seem a bit picky, and
with shutter speeds probably so,
but it is the same phenomenon you
experience with the distance dial
when focusing, and there you are
well advised to be precise!
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Setting ASA
on a MINOX Model
B
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The Minox B model has an exposure
meter, mounted adjacent to a dial (yellow)
which can only be rotated by moving the
shutter speed dial (orange), the two being
linked by gears. If the film speed (yellow arrow) has
been properly set, the correct shutter
speed will be achieved by rotating the
shutter speed dial until the clear
triangle (red arrow)
is in the same position relative to
the lines, as the meter needle (brown arrow).
Setting the ASA
(DIN)
STEP 1.
Prior to opening the camera to load new
film, rotate the shutter speed dial until
the black triangle (yellow arrow) is
pointing to the speed of the film to be
loaded.
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When the camera is fully opened, as
when loading film, the gear (green arrow) is disengaged,
allowing the shutter speed dial to be
freely rotated without affecting the meter
dial.
STEP 2.
With the camera fully open, ready to
insert the film cassette, rotate the
shutter speed dial to 100 (blue arrow). As a
reminder, you will notice that the small
dot above the 100 is red rather than
black,.
After loading the film cassette, close
the camera. BE CAREFUL WHEN CLOSING
THE CAMERA! If you have moved the
shutter speed dial while the camera is
open, the gears may be misaligned and not
mesh. Adjust the shutter speed dial very
slightly to align the gear teeth.
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Notice that the black triangle under the "ASA"
has small marks on either side. These represent 2/3
of a stop increase or decrease. Thus, it is
possible to accurately set a film speed of 16 on
the low end and 640 on the high end while using the
standard "100 shutter speed" setting.
Since there is no ACTUAL
linkage between the meter and the dials, it is
worth asking, what would be the effect, when
setting the meter, of setting the shutter speed
dial to 200, or 500, or 50, or 20, rather than the
nominal 100.
In fact, we are dealing with a camera which
ended production during the last century, somewhere
between 28 and 42 years ago. The meter, and perhaps
even the shutter speeds, may not be precisely
accurate. Added to that are the unique attributes
of YOUR processing system
and materials, which WILL
affect the effective film speed. To complicate
matters further, I frequently use film which is
either slower than ASA 25, or faster than ASA 400.
My preference with the Minox B is therefore as
follows:
- Using the above procedure, set the "ASA" to
the manufacturer's recommended value and load
the film.
- Find a scene in which there is a large
shadow area with luminance you would like to
place Zones II, III, and IV.
- Take a reading and note the meter's needle
position.
- Make a series of exposures, bracketing the
recommended exposure by several stops.
- After development, select the frame that
most accurately provides the desired shadow
detail (Zone II through IV).
- ... and ...
- With the camera closed, set the meter to
the setting recorded in step 3.
- Fully open the camera and set the shutter
speed to that used when making the best
frame.
- Close the camera and move the shutter
speed dial to 100.
- If the black "ASA" triangle is
pointing -
- between the 25 and 400, leave the
shutter speed at 100 and record the ASA
value.
- to the left of the 400, move it to
ASA 400 and record the corresponding
shutter speed.
- to the right of the 25, move it to
ASA 25 and record the corresponding
shutter speed.
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The table at the right shows THEORETICAL values for
setting the film speed for emulsions
ranging from ASA 5 to ASA 4000. It has
been my observation that good results can
be obtained by using a Personal Exposure
Index (ASA) one stop faster than that
derived with the classic "0.1 density
above film base plus fog for Zone I"
method. Thus, AgfaPan 25 might provide
satisfactory results with the meter set to
ASA 50, and Fuji Super HR, which has a
speed on the order of ASA 3-6, works well
in normal outdoor light with the B set at
ASA 12.
Since the meter reads a rather broad
area, the luminance range and distribution
have a major influence on the optimum
exposure. It is important that some
experimentation take place to find the
most useful setting for each film.
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