Zone System film speed changes

After 20 years as an amature B & W photographer I'm finally starting

to understand the Zone System. It takes me a long time to grasp some

of the finer aspects.

 

I understand, I think(?), metering, place and fall, and development

to achieve desired tonal range. But, as yet, I'm struggling with the

reasons for changes in film speed. I'm using Agfapan 100 and starting

to use Ilford HP5+ 400 in 4x5. The Agfa I rate @ ASA 100 and have

great success with it. The HP5+ is new to me. Most of what I've read

in forums and books indicate rating HP5+ @ 200 ASA for Zone System

metering/procesing. Some reading I've done suggest a different ASA

for different degrees of contraction or expansion development (minus

and plus).

 

Can anyone here clear this up for me. My brain cells are staring to

hurt.

 

Much appreciated.

The Zone System is simply a matter of controlled exposing combined with adjusted processing, or either alone. Since there are so many personal variables, one MUST test for ones own standards, and standardize the way one handles the processing procedures. And each new emulsion and developer must be tested, and copius notes taken. Read "The Negative"by Ansel Adams.

The numerical value of your own ASA has a lot to do with the

developer/film combination, your len's degree of contrastiness,

and also how you visualize and meter a scene. That said, I rate

HP5+ at 320 in D76 and ID11 or Rodinal, but at an easy 400 with

Neofin Blue. I shoot a lot in Minus 2 or Minus 3 situations. In

these cases I might add 1/2 stop exposure. When I process, I

aim for a Normal negative that prints well on a grade 2. If in

doubt, I process the negative to be on the flat side. I find Normal

or slightly flat negatives easier to print than overly contrasty.

 

My Zone system methods are based on my modern Sironar N

MC. If I am shooting with an uncoated lens or single-coated, I

add ONE to the processing, thus an N-1 negative shot with an

uncoated lens is processed NORMAL.

You need on the film a limited range of contrast that can be easily printable (all the zones) in a "normal" paper as the Grade 2.

 

The whites of the print are controlled by more or less development time of the negative; but if you have a condenser enlarger (for instance), you will look for a less "darker" negative and develop for a shorter time.

 

This shortened time could be correct for the highlights but too short for the lowest density areas on the negative (zone I), that could appear too much soft than desired (darkest areas on the print without "control").

 

If you give bit more exposure (like changing to a lower ASA setting), you can improve the density in this lightest areas and to set the desired blacks with detail on the prints...

 

Small changes in the dev. time don't change too much the density in the zone I, but a big change in the development(like when you need a N-2 process) need to be compensate for this zone I, adding more exposure.

 

Hope this helps (and please, excuse me if I am too obvious),

Steve, to answer your question in a short way, the iso of your film is set by you through experimentation. You want your iso to be such that when you process your film at the manufacturers time and temp you will get a density in your shadow regions(on the neg) that will translate into shadows with slight detail(zone 3). to low a film speed and you will get very little black in your low value regions. And to high an iso you will get shadows with no detail at all in the zone 3 areas. If you set your film speed at the right iso you will get good shadow detail and then after you change your development time to it's proper time you will get your highlight(zone 8 or 7 depending on if you want a 5 or 4 stop contrast spread between your important highlight and shadow regions) where it will give you a good print at say a grade 2 paper contrast. Remember that you expose for your shadows and develope for your highlights. You want a negative that will print good shadow detail and also highlight detail on your choice of paper with little extra exposure manipulation. When the scene brightness range is such( more than 4 or 5 stops depending on your contrast range you set with your exposure/development scheme) that you can't get the negative to hold that much contrast range then you need to contract(less development time) your processing time. and if you contract it very much you will need to add some time to your exposure. Each film will be different as you are finding out. And this is where you will need to calibrate your system. And it is very easy to do. Each camera will give different times and each film will be different. I hope this muddies it up a little better for you. Let me know if you require further help. James