Thanks, David/Collin/Paul.
I think I understand, now.
I was thinking that since the snow was so glaringly bright that it would
throw the meter off irrespective of the actual subject -- assuming the
subject isn't the snow itself.
But, as I understand you all now, as long as there's a dark enough
counterpoint to the snow within the frame, the metering will average
out. My question in that case is, does the ratio of dark to light
matter? Say, if you have a snowy field and a small black dog in that
field, taking a photo of a distant grey object, is that enough to get
the correct averaging? Or do I need to compensate for the dominance of
the snowy field within the frame?
In other words, does the meter average the difference between the
darkest and the brightest objects in the frame, or the total amount of
darkness and brightness in the frame?
Thanks again, y'all. I do appreciate your patience.
-- Walt
On 2/9/2011 9:18 PM, Paul Stenquist wrote:
On Feb 9, 2011, at 10:05 PM, Walter Gilbert wrote:
Thanks for the explanation, Collin.
When Paul said to overexpose, I was actually thinking it sounded counter-intuitive --
that you'd want to under-expose in a snowy situation. But, it makes sense now that you
explained that the meter "assumes" a neutral grey.
So, I'm assuming that in extra-low-light situations, I'd want to under-expose
by a couple of stops in that case.
No. It's not amount the amount of light. The reason you overexpose snow or
anything else that fills your frame with white is simply because it's white and
very reflective. Like Collin said, the meter assumes everything is 18% gray and
reflects the amount of light that an 18% gray surface would reflect. So
shooting a white subject in low light, you would still overexpose. Shooting
something totally black, you would want to underexpose by about one stop, since
black doesn't reflect much light.. Again, using the gray card and exposing to
the meter reading is usually better in really tricky lighting situations.
Another alternative is an incident meter, which measures the light source
rather than the scene. As with the gray card, you don't have to correct for the
reflectivity of the subject when shooting with an incident meter.
Paul
Glad I found this out before getting too deep into the roll!
-- Walt
On 2/9/2011 8:40 PM, Collin Brendemuehl wrote:
No!!! Always overexpose snow by 2 stops.
Why?
Because an averaging meter expects a mid-gray tone.
The result will be gray snow unless you open it up,
either with the shutter, aperture, or both.
You can also change to iso32.
Sincerely,
Collin Brendemuehl
http://kerygmainstitute.org
"He is no fool who gives what he cannot keep to gain what he cannot lose"
-- Jim Elliott
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