A-ha, I'm aiming using the chart you gave me. Ansel Adams is aiming using Zone VIII. The top of 7 1/3 stop (my Normal) is less than 8. So it makes sense that if you stick to using Zone System to decide a NDR you would choose a higher density aim, than if you were aiming based on another system where 7 1/3 stops is Normal.
7 1/3 is larger than 7, so shouldn't 7 1/3 have a larger NDR? Just to be clear, this is not just a simple case of different methodolgies. The paper LER is the basic method to determine the aim negative density range for a paper. A NDR of 1.25 simply will not fit on a LER 1.05. The only possible explanation as to why the Zone System 1.25 target density range determined from testing is able to print on a grade 2 paper with a LER of 1.05 is because of the addition of flare (which is not factored in with the testing) in normal shooting conditions. Remember in camera Zone System testing has minimum to zero flare.
Oh I got the counting of "towels and clothespins" wrong. They're both essentially 7 stops for normal, let's make them both 7 and ignore the 1/3 until reason forces us to hunt that down. The sheet you gave me highlights 7 stops for normal.
Originally Posted by Stephen Benskin
On the next page of The Negative, Adams mentioned the tendency of manufacturers to make papers a bit "shorter scale" for Grade 2 (so you better test for yourself), he also qualified his numbers as being what works for him. And many photographers are using variable contrast paper (which makes it less important to get it right).
But here's where the flare is: The enlarger lens.
Last edited by Stephen Benskin; 05-15-2013 at 08:55 PM. Click to view previous post history.
So you've put a little flare into the paper curve by enlarging? That's going to help, so you don't have to make a stepping stone diagram that goes up over and down to accommodate more transfers - your fourth quadrant should arrive at the preferred tone reproduction curve.
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Bill, interpreting the reproduction curve has to do with subjective tone reproduction , and those types of discussions don't go well, but to briefly sum up some of the factors involved in calculating exposure.
Originally Posted by Bill Burk
The image illuminance comes from the incident exposure meter calibration equation.
A^2 / T = E*S / C
E = incident light, in footcandles
S = film speed
C = Exposure constant
A = f/number
A^2 / (A*S) * C = E -------- (16^2 / (1/125) * 125) * 30 = 7680 footcandles
Average reflectance in the reflection exposure meter.
R = L / I
R = Reflectance
L = Luminance
I = Illuminance
The exposure constants for reflected and incident exposure meters can be substituted for the actual L and I values.
R = K * pi/ C ------- 1.16 * pi / 30 = 0.121 12%
Exposure for Lg (average luminance).
q * L / A^2 = E ---------- 0.65 * 297*10.76 / A^2 = 8.11 ---------- 8*1/125 = 0.064 lxs