Dev control for b/w filmsgreenspun.com : LUSENET : B&W Photo - Film & Processing : One Thread
I know b/w developing is contingent on the shooting/printing style of the photographer, but... Is there a manufacturer spec for 18% grey in terms of statusM density? Like a LAD for color? For example, if I develop PlusX (exposed normal) in D76 straight, 18% grey should yield a density of 1.20 or something? B/w is not like color as there are many variables, but the manufacture must come up with suggested times of development of various stocks using some sort of aim middle grey.
-- Doug Delaney (firstname.lastname@example.org), November 01, 2000
Zone V should fall around D=0.7
-- Bob Atkins (email@example.com), November 01, 2000.
Zones should only exist in the print and in the imagination of the photographer, they are meaningless when applied elsewhere.
To use zones as some sort of fixed reference is completely contrary to their intended use as an aid to pre-visualising the finished image. If you always use 18% grey as zone V, you might as well abandon the zone system altogether.
-- Pete Andrews (firstname.lastname@example.org), November 02, 2000.
WOW, to follow Pete's line of thinking the negative has nothing to do with the final print. He also seems to think that calibrating your system for exposure and development is not part of the zone system, amazing.
-- Jeff White (email@example.com), November 03, 2000.
That's not what I said at all Jeff, but perhaps more "Zone Zealots" should follow the original spirit of the zone system, in simply being an aid to pre-visualising the final print, and not turn it into a technical guide for sensitometry anoraks.
-- Pete Andrews (firstname.lastname@example.org), November 03, 2000.
It's funny how easy it is to respond with a hint of irritation when using email. It's so fast and easy to type (as opposed to write), that first thoughts get into the mix rather than friendly banter.
At any rate, the first line of the question was there to make clear that I understand that zone V means anything to anyone and that it is simply a tool for visualization and little more. Anyone worth his salt understands that. What I was curious about was if I shoot a grey card with say PlusX rated as the manufacturer specifies (80ASA daylight) and process the film with my favorite developer, how will I know if I ran the neg according to manufacturer specs? What does Kodak say 18% grey (not necessarily zone V, we know) should be in terms of density (statusM) if all goes as Kodak would like. They list suggested dev times for various developers and they derive those times by having aim densities for Dmin, step 11, and Dmax I guess, right?
I know this has nothing to do with creativity, nothing to do with much of anything other than a curious guy posting a question.
-- doug delaney (email@example.com), November 03, 2000.
Doug. I apologise for introducing a tone of controversy into what should have been a straightforward Q & A post.
The answer to your question seems to hinge on where the toe of the D/logE(orH) curve is pinned.
As an ongoing project, I've been transferring the manufacturers rather vaguely drawn curves to a spreadsheet, as and when the need arises. This enables you to get quite accurate density readings from them, rather than just estimating what density base+fog is, or where 1.2logE units from the toe falls.
Anyway, it seems to me that Kodak place their baseline at the point where there is a just detectable upturn in the curve, and put 18% grey 5 stops up from this point. (or 4 stops up from the point where there would be readily detectable detail on the negative)
This fits in neatly with the old 'U' and 'O' settings on Weston meters, and also with the zone system.
Unfortunately, I don't use Plus-x, (I much prefer FP4+) and haven't read the x,y co-ordinates from Kodak's curves into a spreadsheet, so I can't give you any density value. You'll either have to muddle by with a ruler on a printed version, or convert the curves yourself. It also appears that Kodak's 'preferred' development times give sets of curves that fit with the zone systems N, N-1, and N+1 etc. A line through a mid density gives approximately 0.3logE spacings of the curves.
-- Pete Andrews (firstname.lastname@example.org), November 06, 2000.
How does this differ from my original answer of D=0.7
If you read Adams' "The Negative" you'll get most of the info you need, but basically a negative exposed as a midtone (zone V if you like, 18% grey if that's what you think a midtone should be) should have a density around 0.7. The exact density depends on whether you're using a diffuser or condenser enlarger, since it's zones in the final print that matter, but if you don't end up with D between 0.65 and 0.75 then it's likely you're doing something wrong (or at least something odd).
Manufacturer's suggestions for "normal" development times are sometimes so far off that it makes you wonder just how they DO decide on them! Technically I assume they develop to give the correct gamma and toe point for the ISO specification rather than aiming for amy particular "midtone" density.
-- Bob Atkins (email@example.com), November 07, 2000.