Are there any "rules" for using ISO?

Started Apr 3, 2013 | Discussions thread
OP GreenMountainGirl Contributing Member • Posts: 684
Re: Are there any "rules" for using ISO?

Barrie Davis wrote:

For your future assistance, make a note of these important facts about metering....

The lightness or darkness of the tones in the subject are of little importance to what shutter speed/aperture combinations will yield correct exposure.

That's simple, there are only two factors which determine correct exposure...

(1) The strength of the light falling on the subject,


(2) The ISO value currently in use on the camera.

Makes sense that the light itself is determining rather than reflectance.

That is why methods of determining exposure WITHOUT pointing a light meter at the subject are more reliable and much more consistent. I'm talking about separate Incident Type light meters with a white plastic light receptor dome (flash meters are of this kind)...

I am not familiar with different types of light meters, have only used one hand-held, the rest were in my cameras.

... and even simple "incident light-strength rules" derived from scientific tables can and do beat a camera meter for accuracy a lot of the time... the most famous of all, the Sunny 16 Rule, which states....

When shutter speed is set to reciprocal of ISO in use (thus 200-ISO = 1/200th second)
correct exposure is as follows..

Clear Sun (sharp shadows) f/16
Hazy Sun (soft shadows)..........f/11
Cloudy Bright (no shadows)......f/8
Cloudy Dull (as when raining)...f/5.6

There is more to it than that, like shooting in snow or on the beach, but basically the whole thing can be written on one side of an index card...

I have heard of the Sunny 16, but only the f/16 part, not the ISO reciprocal shutter speed.  You say there is more... I would love to hear it, especially if it will work for me!

Hey! That's enough to be going on with...

I hope it was interesting, and not too long.

It WAS interesting, and I can handle the length just fine!

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