Simplified Zone System - Custom ISO

Testing your camera meter- Customizing your ISO#
Film speed is determined by the exposure that reaches Zone 1 density on the film. (.1nd above base+fog)

The target you photograph should be smooth toned, evenly lit, neutral in color and large enough to fill the frame.
Set your meter to the manufacturers film speed (iso#).

Point your camera at the subject and set the lens and shutter to give the recommended exposure.
Choose a shutter speed that requires an f/stop of approximately f2 or f4. Don’t change the shutter speed.
1- Make your first exposure- this will be middle gray Zone 5.    f/stop____ Shutter 1/_______
2- Make your second exposure  Close your lens 4 stops- (count 4 full stops -  eg. 4>5.6>8>11)        
    this should be Zone 1     f/stop____ S 1/_______
3) Make 4 more exposures:
Bracket the second exposure (Zone 1) in half stop increments - record the exposures  
(eg. If 2nd exposure was f11, shoot f8, f8/11, 11/16 and f16)
+ ½   f/_______  half stop more exposure
+ 1   f/_______ full stop more exposure
- ½   f/_______ half stop less exposure
- 1   f/________ full stop less exposure
Develop the roll normally- be careful to adhere to time and temperature with consistent agitation.

When the film is dry, evaluate it for the frame is the true Zone 1 exposure
Just perceivable tone above clear film( .1 neutral density above base + fog).
This frame indicates your calibrated film speed for your camera, lens and meter.

If the second exposure is correct, you use the film speed recommended by the manufacturer.
- ½f stop is correct, increases the iso# (400 speed film goes to 600)
- 1f  stop doubles the iso (400 speed film goes to 800)
+ ½ f stop reduces the iso  (400 speed film goes to 300)
+1 f stop reduces the iso by half (400 speed film goes to 200)

Use this new film speed for this film and camera combination.

Paul Pearce