A bit about .. Setting Shutter Speeds

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.

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.

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.

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.

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!

Setting ASA on a MINOX Model B

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. BEFORE opening the camera to load the new film, rotate the shutter speed dial until the black triangle (yellow arrow) is pointing to the speed of the film to be loaded (in this case ASA 25).

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 with those in the exposure meter.

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:

  1. Using the above procedure, set the "ASA" to the manufacturer's recommended value and load the film.
  2. Find a scene in which there is a large shadow area with luminance you would like to place Zones II, III, and IV.
  3. Take a reading and note the meter's needle position.
  4. Make a series of exposures, bracketing the recommended exposure by several stops.
  5. After development, select the frame that most accurately provides the desired shadow detail (Zone II through IV).
  6. ... 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.

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.