ZONE GUAGE OPERATION INSTRUCTIONS
By Dennis O' Connor (Area 20)
- The operation of the ‘Zone Gauge’ is based in the principle that all light meter readings are based on ‘Zone V1 of the zone system. That means that a light reading taken from any subject will give a reflectance value of 18% grey irrespective of the colour or brightness of that subject, this can lead to overexposure or underexposure of that subject. Due to this, adjustments have to be made to meter readings according to;
- The subject .
- The way in which the subject is to be shown.
Example. A reading of a snow scene will cause a camera to underexpose, producing grey’ snow, unless adjustments to the meter reading are carried out.
The ‘Zone Gauge’ allows the photographer to immediately calculate the correct exposure and adjust the camera controls to avoid this occurrence.Operation.
1. Take a meter reading from the subject you want to expose for.
2. Note the camera/meter readings for;
- aperture
- speed
3. Set the F/Stop dial so that the indicated value is opposite the number 5 (Zone V).
4. Next set the speed dial number indicated also opposite the number 5 (Zone V).
5. Now rotate either;
- the f/stop dial To give the correct aperture/speed
- the speed dial combination for your subject.
- both dials
Example.
A reading from light skin indicates 1/30 @ F16. This will cause underexposure of I stop. To correct this using the ‘Zone Gauge’.
- set the F/Stop dial so that F16 is aligned with ‘5’ (Zone V).
- set the speed dial so that ‘30’ is also aligned with ‘5’.
The zone system states that a more suitable placement of light skin is ‘Zone VI’. So turn the speed dial so that the ‘30’ is aligned with the ‘6’ (Fl I or Zone VI). You should now get the correct exposure for that subject.
You could get the same effect by leaving the speed dial aligned with ‘5’ and rotating the F/stop dial anti- clockwise I stop.
Once you have set the correct reading, you can read off any F/stop - speed combination to suit the conditions.
You do not have to use whole stop values. If you wish you can 1/2 or 1/3 stop values either side of the correct combination to achieve the results you want.
The reverse face of the ‘Zone Gauge’ has a ‘Subject Brightness Range’ indicator. This is used in a similar manner to the ‘Zone Gauge’.
1. Take a meter reading from the darkest part of the subject and align the value indicated using the 1 -20 dial with the 1st meter reading line.
2. Take a meter reading from the lightest part of the subject and align the arrow on the S.B.R. dial to that value on the 1 -20 dial.
3. Read off the number on the S.B.R. dial that aligns with the 1st reading point. The number indicates the subject brightness range. Printing papers can only show approximately 5 stops difference. If the value you arrive at is greater that (5) you will have to reduce the difference between the lowest and the highest readings. One way to achieve this is to use a reflector to lighten the darker areas and take another reading.