The Mobile Zone Calculator helps you use your spotmeter, either in your camera or handheld, to make zone placements, and determine a range of multiple exposures if necessary. It can also convert your camera’s meter readings into actual exposure values as if you were using a handheld meter.
Camera mode: if you have an exposure compensation dialed in, enter it first.
Handheld mode: enter the ISO speed.
The meter readings come next. If you are using digital or transparencies, the suggested workflow would be:
• Meter a textured highlight and place it on zone VII to prevent overexposure.
• Then meter a detailed shadow and see if it falls within the range of your medium. If you are shooting RAW, this would be in the neighborhood of zones O-II; for .jpg or transparencies, it would be more like zones II-III.
If you are using negatives, either black-and-white or color, the suggested workflow would be:
• Meter a detailed shadow and place it on zone III to prevent underexposure.
• Then meter a textured highlight. There is some latitude here; the expected value for this is zone VIII, but most modern films can record data past zone X.
The meter 2 fall is based on meter 1. If meter 2 falls outside the available range, place it where you want it, and the two indicated exposures will represent a range of exposures that will capture all of your values. Make exposures at appropriate intervals across the range. (If meter 2 falls within the available range, you do not need to make multiple exposures; just use meter 1.) It is recommended to use the same aperture for multiple exposures, varying only the shutter speed, as different apertures will result in different depths of field and other image characteristics.
Camera mode: if you specify the ISO speed, the actual exposure value (EV) will be displayed along with the shutter speed and aperture. This has no effect on the exposures themselves.