Originally posted by jfdavis58 To teach an introductory class on the Zone System would require several items: (1) about six months assuming a three session (3-4 hours each) per week schedule; (2) about $350.00US from every student; (3) access to Adams' The Negative, White"s New Zone System manual; several hundred rolls of black and white film and associated developers (it's much easier with sheet film and a large format field camera); (4) several hundred sheets of B&W paper and developers;(5) A darkroom, fully equipped, with a densitometer (transmissive and reflective); misc other stuff.
But here's some hints: a gray card ain't 50% reflective (or 28% or 22 or...) except in one light! The Zone System ain't about exposure or exposure theory.
And that begs the question: "exactly where (WHAT VALUE OR GROUP OF VALUES) does a gray card produce a peak on the histogram?" I.e. what would you expect?
Well you still peaked my interest as to where the author of the link "fell down".
You may not have to show how to do the zone system but it shouldn't take much work to comment on where he failed....or what he failed to understand.
As to grey cards ect... According to my understanding if you take a photo of a grey card (regardless of light conditions ect) you camera meter will average the exposure to peak around 110 in RGB color space, in gamma 2.2 (sRGB space in other words) but I don't believe this is what you are referring to.
simon brown - Gamma-Correct Rendering Background to monitor calibration and gamma
And I'm sorry for ever mentioning the zone system.
Again not my point nor is any wet chemisty part of the discussion. That said I will finish (actually start) to read the pdf posted (Chuck Gardner "tn explaination of why its not possible to use the Adams' zone system with digital but how range a digital camera can capture can be previsualized" ) in earlier thread that seems to imply the zone system and digital are mutually exclusive (at least according to the title.)..
Addendum: I'm going through the Gardner paper and I (think I) realize what your problem was w/ the zone article I posted. Anyways a few choice tidbits I found interesting:
"Some accused him of bullying Kodak into make 18% gray the standard for its cards when 12% is actually a more accurate value."
"Moving the metering reference point: Since it is the highlight detail which is the benchmark for correct digital
exposure it makes little sense to meter based on a 18% gray value. But since meters are calibrated to display
exposure based on the assumption a scene is the average of light and dark it is necessary to translate the meter
reading from the middle of the range to textured highlights. It's erroneous to think the meter reads Zone 5 and its
simply a matter reading the towel and adding 3 stops to get the reading for correctly reproducing the towel as Zone 8
on the print."
If you still think that you still don't get it.
"ZONES ARE NOT F- STOPS!!! It will be far less confusing if you forget you ever heard of the zone system and instead think in terms of brightest and darkest tone with detail: DS and DH.
In digital pre-visualization system the white towel becomes the benchmark DH and exposure in all subsequent test"
And my favorite:
Why is mid-tone adjustment significant in digital photography?
The inherent nature of the capture process often results in a digital image which appears to have less contrast than
when the scene was viewed by eye. Because the dynamic range of a given camera is fixed it is not possible to
expand the overall range of the capture (i.e. add more shadow detail to the captured image) but by shifting the tonal
value of the midtones closer to either the highlights or shadows it is possible to create more or less apparent contrast
and with it an illusion of more detail. For example if one takes a flat looking image, opens it in levels and does nothing
more than nudge the middle sider towards the right side (highlight end) of the tonal scale the image will appear to
have more contrast and detail. There is no actual increase in resolution, but eye is fooling into thinking there is
because our brains equate darker shadow transitions with dimension and detail............"