Exposing and measuring zones

If I expose a graycard to three sheets of Tmax at Zones V, VIII and

IX (3 stops, and one stop) would the "correctly" developed negatives

once placed on a consistent light tabe and read with my baffled

meter also result in an equal distribution, i.e the Zone V neg will

be transmitting 3 stops less light than the Zone VIII neg, and one

stop of transmission between Zones VIII and IX?

 

I hope that doesn't sound too convoluted.

 

thanks,

Aaron

The range in density of a negative is quite different from the range of relative light intensity of the subject being photographed.

 

If you're developing for a condenser enlarger, the Zone V density would be about 0.6 above film base plus fog. The corresponding densities for Zones I and VIII are about 0.1 and 1.2 above film base plus fog respectively. Density varies by about 0.3 per stop so there are about 2 stops (0.6 density) difference between Zones V and VIII and about 1 2/3 stops (0.5 density) difference between Zones I and V.

 

I've done what you're describing with good sucess when doing film speed and development testing - you just need the zone/density numbers to work toward. I usually use just 2 points for testing: Zone 1 and VIII. As long as the densities are what I want for those Zone exposures then I know my film speed and development are OK.

 

Film manufacturers publish curves showing density vs relative exposure which should give you a starting point for densities. The website http://www.cicada.com/pub/photo/zs/ has some interesting info on film density vs exposure.

Aaron,

 

The simple answer is NO. The density values of zone V, VIII & IX will depend upon your printing setup. The values will be different if you are using a diffusion enlarger versus a condenser enlarger. Some photographers will develop their film to print on grade 2 paper and some for grade 3 paper. There are suggested densities for Zone V and Zone VIII, but most refine the process for their particular setup. You might be able to use the set up you describe to evaluate unknown negative densities if you have calibrated densities for reference, but "transmittion" negative densities do not translate directly to F/stop distribution.

 

Paul

I actually scan them with an Imacon, so I'm concerned about the absolute values (I and IX), and if my rated ISO+dev time gives a proportional distribution of values. Once I know the time that gives proportional density to the Zones, N+- is easy to figure out.

 

Paul, you said that they don't translate directly, is there some way to figure out how they do map?

 

thanks,

Aaron

No. There is not a one-to-one relationship between subject brightness range (SBR) and the density range seen on film, unless you are making a concerted effort to create one for experiemental purposes.

 

In fact, the whole point of the Zone System is to fit the given SBR into the a density range on film that you can easily print on photo paper in the darkroom. The film is an intermediary - a tool to use to shoehorn the typically wider SBR of the scene into the constricted density range of the paper.

Ian, I just reread your post. That might be what I'm looking for, despite the fact I don't have a densitometer. How did you come by 0.3?

Bruce,

 

"the whole point of the Zone System is to fit the given SBR into the a density range on film that you can easily print on photo paper in the darkroom" It is the same thing for scanning and printing. Dmin and Dmax of film will always outstrip output materials. That's why I'm so concerned about getting the range correct because when I do want N+- development, I know that I'm getting a negative with the optimal amount of information. I completely agree, the negative is never the end all be all, (unless you're seriously into contact printing).

Aaron, the 0.3 density change per stop is logarithmic - log 2 is 0.3. Neutral grad filters they are typically in 0.1 density increments so if you want a 2-stop grad filter it is 0.6 density. 10^0.6 = 4 (2 stops).

 

I check negative density using an incident light meter which has 0.1 stop resolution. I place the meter on the enlarger table and project the negatives onto the meter dome. I know that the meter is fairly accurate and it seems to be repeatable.

 

Years ago I got into the habit of exposing frames 36 and 37 of most rolls at Zone I and VIII as a test. Since I load my camera in a way that gives unexposed film at the start of the roll I've got my Zone 0 for reference density, and since my negative sleeves hold 7 rows of 5 negatives I use only 35 frames per roll. So what to do with the other 2 possible frames? It seems like a useful way to justify a quirky habit.

Aaron,

 

The only way I can think of to map waht you want is to buy a calibrated step wedge from Stouffer Graphics at Stouffer.net. You can measure the calibrated set wedge with your "set up" and make a table for future use.

 

Paul.