For more details, see Mark Roberts reply to me. I was incorrect about
the ANSI/ISO bit (it's an ANSI standard, not ISO), but the rest is
correct, and I didn't get one bit other than the Luminance portion from
the Internet btw, so it's not an Internet myth.
Note that according to the manual for my Weston Master II, the angled
grey card method you note as incorrect is in fact the correct way to use
a grey card.
On a Luminance scale, L=50% is at 18% grey and Zone V by default. Of
course, you can always put Zone V elsewhere, but that makes for about
the best starting point one can hope for.
-Adam
graywolf wrote:
Another one of those Internet myths. When first I heard that one I
wrote Sekonic and asked. They understandably did not bother to answer,
so I went out with my gray card and my Sekonic L-308B and checked it
out. Interestingly enough an incident reading, and a properly done
Kodak gray card reading, gave exactly the same exposure.
However if I did the gray card reading as I have seen suggested on
those same Internet sites, with the card angled between the meter and
the light, instead of perpendicular to the meter, guess what? Yep I
got something like a 12.5-13% gray reading. If you use your meter and
gray card incorrectly you get an incorrect reading. Then because you
are another one of those experts you tell everyone they are fools and
that their meters are not calibrated to 18%. BTW if you do not have an
incident light meter to compare to how can you tell what your
reflected light meter (dedicated or built into your camera) is
calibrated to? The difference between 12.5% and 18% is less than 1/2
stop, you probably would not notice the difference except in the most
critical situations. Also meters are actually calibrated with a
calibrated light source, not by measuring a reflectance, gray or
otherwise.
Now lets take that 18% = Zone V thing that AA lobbied so hard for . If
we put Zone X at 100%, it can not be any higher than that by
definition (of course you can chose to burn it completely out if you
want). Then Zone V is 3.12% reflectance. Your 12.5% would be Zone VII.
And 18% somewhere between Zone VII and VIII. That kind of blows that
theory out of the water. Zone V is what ever you want to show up as
middle gray on your b&W print, and that is all it is.
Just so folks don't treat me as another Internet expert, I suggest
they go out and do some experiments. What I, or anyone else, say can
be mistaken, you should only trust your own methodical
experimentation. How else can you find out just exactly what your
equipment does in any given situation.
http://www.graywolfphoto.com
"Idiot Proof" <==> "Expert Proof"
-----------------------------------
Adam Maas wrote:
There is a photographic myth with 18% grey. The myth is the idea that
your camera's meter assumes 18% grey, which is incorrect. Meters
assume roughly 12.5% grey (there is an ISO standard). Grey cards are
18% for the reason graywolf explains, as well as due to intense
lobbying of Kodak by Ansel Adams (Who wanted 18% grey because it is
50% luminance and right in Zone V). But overall, most scenes do
indeed average out to 18% grey.
-Adam
graywolf wrote:
18% gray is not a myth. It is just that most people do not
understand where it comes from. If you go out and measure thousands
of scenes with an averaging meter, the average of those exposures
will come out to 18% gray. So 18% reflectance is an average value,
where you want to put that average value in your particular photo is
up to you. It certainly is not cast in concrete (which is usually
near 18% gray, by the way <grin>).
graywolf
http://www.graywolfphoto.com
"Idiot Proof" <==> "Expert Proof"
-----------------------------------
Bob Shell wrote:
On Dec 3, 2005, at 9:26 PM, Rob Studdert wrote:
I think blanket statements regarding optimum print resolution are
pretty
useless as the printer in concert with the driver its settings
and the paper
type determine the optimum print resolution. Also I never
experienced problems
printing images with resolutions that weren't multiples of the
natural printer
resolution on any inkjet print systems.
I agree. The idea that you have to use multiples of the printer's
stated resolution (itself a mythological beast) is another
photographic myth, like 18% gray.
Bob
