Metering off Sky

[elguapo]

<DELTE>

[sonshine_rae]

My understanding.. is that by metering off the sky or off greenery.. You are metering the ambient/incident light. Instead of reflected light........ so the tonality of your subject (whatever that may be) should not matter.

Whereas if you meter off the subject it will be reflected metering, and hence your color tones will either absorb, reflect etc different amounts of light, and sometimes cause under or over exposure because of that.

HTH's :),
and often times the easiest way to get an answer to such things.. is to give it a try yourself :), if you get a spot on exposure, then that means it'll work just fine.

[PhotosGuy]

Some people read a blue sky, some use green grass. This will always work for me: Don’t have a gray or white card, or hand held meter with you? “Film tricks” can help you out.
Need an exposure crutch? (http://photography-on-the.net/forum/showthread.php?t=89123)

[gasrocks]

Green grass will only work sometimes. Not all grass is the same green. It has lost me enough shots to never try that again. The darkest part of the blue sky is 18% so you could use it to meter for any subject on the sun.

[PhotosGuy]

Just for clarification, knowing and using other methods to get the correct exposure is great, but I'm trying to understand what Peterson means in "Understanding Exposure," when he writes about meting off the sky.

I've been doing more research, and from what I can tell, a sunny blue sky is a giant gray card since it's reflectance is about 18%-20%. So metering off a blue sky will give you the correct exposure if your subject is in full sun also.

Is my understanding correct: when using a sunny blue sky or a gray card, you just adjust your camera settings the way you want to get the correct exposure for it, then ignore the meter when photographing your actual subject. What gasrocks said. An ideal "blur sky" of ideal "green grass" can be used for a substitute. How often will you get that?
These substitutions were used before the histogram became available. We don't need them any more. Use your hand & adjust as I showed you in that link & you will be right 99% of the time. Is my understanding correct: when using a sunny blue sky or a gray card, you just adjust your camera settings the way you want to get the correct exposure for it, then ignore the meter when photographing your actual subject. Yes. Since a gray card will give you the correct exposure for any subject in the same light, the blue sky will do the same. Therefore, it doesn't matter what color your subject is? Probably now. Some older meters were more/less sensitive to some colors. Leaving aside for a moment that you have to adjust your exposure to compensate for the different between a gray card and you palm or grass--the same concept works when taking a meter reading from them? ?