light metering???

[david clark]

Can you point a spot meter at an overcast sky or into a fog and get a reading that you can translate to a zone? And what about blue sky? how can you determine the tone you would like the sky to be? Thanks.

[Donald Miller]

A spot meter will give you an indication of an exposure that will render as Zone V. This would be the exposure that would give you a negative density that would translate to a print tonal value of an 18% gray card if your EI for the film and your development has been determined. If you want to give something a tonal value that is one Zone higher (lighter) in value you would give one more stop exposure then what the meter indicates. If you want to give the metered object a one zone lower (darker) print value you would give one stop less exposure then what the meter indicated.

[Leonard Evens]

Whenever you use the Zone System, you have to decide where you want a particular element of the scene placed. You need to look at different elements of the scene in relation to one another to decide that. On an overcast day, you probably have relatively low contrast, so you may want to expand contrast. The sky on an overcast day should probably end up as a fairly high value.

On a sunny day, without a lot of haze or smog, the sky close to the horizon away from the sun might be about Zone VI but a bit higher up about Zone V for a normal scene. But haze and smog and time of day can vary that quite a bit.

[Tim Curry]

Don's answer gives you exactly what you asked for. I would add one more variable. In order to understand that reading of sky, fog or cloud, you need to see the relationship between the metered object (cloud etc.) and its surroundings. What is the darkest object in the image, the lightest and where does the whole image fall on a zone system scale?

Seems to me an understanding of the whole image is needed, not just the reading of one portion of it, but how it relates to the range of values within the entire image. Before a decision can be made about the actual exposure and subsequent development, give a proper translation of values in a finished print. All of this must be considered.