Film testing

timbo10ca · Feb 7, 2007

I am in the process of trying to do some film tests according to the Zone System in 35mm. I think understand the concept - Find the correct film speed that gives you detail in Zone 3, then find the development time that gives you good detail in Zone 8. Then it all got turned on its ear when I was reading a thread at P.net and someone mentioned Barry Thornton's "Edge Of Darkness". He sais that for depending on the brightness of the scene, rate the film at box ISO (cloudy, no shadows) and develop as recommended, and to rate the film at 1/2 box iso and decrease development by something like 20-30% (bright sun, sharp shadows). I thought that film testing was to give you the film's speed, regardless of the light outside! Is his vernacular just another way of deciding on exposure and N minus development for scenes that have a long exposure gradient for "non-zonies"? I'm trying to wrap my head around his use of box ISO for cloudy scenes and normal development though. It seems that film is always slower than its box ISO.....

Thanks again,
Tim

Donald Miller · Feb 7, 2007

Hi Tim,

I have not read the Thornton book but based upon what you say, it appears to eliminate testing film speed.

I will go on to say that film speed is not a fixed factor (no matter if this is Thornton's recommendation or that of Ansel Adams or someone else who claims this to be true). Film speed will vary depending on development. Development is of course tied to the inherent scene brightness.

Film speed is not always slower than box speed. It depends on development.

Michel Hardy-Vallée · Feb 7, 2007

Tim, Thornton's method is just a heuristics, simplified way of dealing with expansions and contractions. It's just based on statistics of usage, not on actual sensitometric data. The point is that most 400 ISO film usually end up being closer to an EI 200 in practice. All the rest of his calculations are relative to this regularity, but it's a shortcut, not actual knowledge about your film.

If you want to know how your film behaves, you have to go through the experimental process of EI/dev time using whatever method you see fit.

reellis67 · Feb 7, 2007

My understanding of the method desrcibed in that book is that it is the old "Expose for the shadows, develop for the highlights" method. I should also add that I use this method and it has greatly improved my ability to control my negatives. I now get negatives that are always in the 2-3 range with roll film, and almost always right on 2 for sheet film where before I was ranging from 0 to 4 on any given roll. It's not as precise as other methods, but I've seen photographs that are stunning which were made before light meters existed so I'm no overly concerned about it myself. Everyone has a system that works for them, I would suggest that you try it out and see what you think before discounting it.

- Randy

joshverd · Feb 7, 2007

timbo10ca said:
He sais that for depending on the brightness of the scene, rate the film at box ISO (cloudy, no shadows) and develop as recommended, and to rate the film at 1/2 box iso and decrease development by something like 20-30% (bright sun, sharp shadows)......

An old professor of mine used the same system. I used it a couple of times, and it worked quite well. This has to do with increasing contrast with increased development. So to get a standard amount of contrast from scenes varying in contrast(on different rolls, mind you). You use this expansion/contraction development. For more contrast: underexpose/overdevelop, for less: overexpose/underdevelop. If you want sensitometric data, I might be able to dig it up, let me know.

There are many ways to skin a cat, do whatever way makes it taste good.

Good luck.

Josh

nworth · Feb 7, 2007

There are lots of film testing methods to get a good personal film speed and development time. Ansel Adams and Phil Davis are a couple of others who have given good, reliable methods in their books. Barry Thornton was a very practical photographer. He has given two fairly easy ways to go. The first you mention (find the exposure that gives good detail in Zone III then find the development that give good detail in Zone VIII) is a practical formal method that is generally equivalent to any of the others. It requires selecting an appropriate test scene, some real testing, and some patience, but, done right, it will guarantee good results from that combination of film and developer. The second (rate the film at 2/3 to 1 stop less than the ISO value and develop 20 - 30 percent less than recommended) is a rule of thumb he found worked with most films and developers. You may have to tweak it a bit for your technique, but it will generally work.

Chuck_P · Feb 8, 2007

Basic concept of the ZS:

The placement of a particular reflectance within the scene on a particular zone within the scale of zones i.e., usually from zone I to zone V. Read Fred Picker's Zone VI Workshop. It's great for someone new to ZS (get AA's "The Negative" for that matter, but I would start with Picker's book first). You do not have to find a personal film speed right off the bat to be able to use the ZS, although you should eventually become aware of what to do when your low value placements do not yield the density in the negative that you anticipate.

I recommend rating your film as per the box speed, practice with some low value shadow placements for exposure (would be best if your 35mm camera has some degree of spot metering), develop the film as per the manufacturer's recommendations. I personally would not be messing around with film testing and variable development until you have a firm grasp of the basic tenet of the ZS: i.e., the "placement" of values on the exposure scale and determining where other values "fall" (a spot meter makes such determinations easier, however).

These are just some suggestions. When I was learning the ZS, I did exactly that----I rated my film as per the box speed, developed as per recommendations for the developer I was (and still am) using. I did this until it became intuitive as to what was occurring based on my actions. Then other aspects such as plus/minus development, filtration, etc...gently fell into my understanding. I'm a 120 user and I'm getting along just fine with ZS "stuff".

Just a suggestion---good luck and regards.
Chuck

Bob F. · Feb 8, 2007

If you want the late, lamented, Barry Thornton's thoughts on testing go to the website www.barrythornton.com - it was put back online after his demise by AWH Imaging (Andy Hollingsworth).

There are several articles on film testing there that go beyond the general "expose for the shadows, develop for the highlights" advice.

Cheers, Bob.

Steve Smith · Feb 8, 2007

I have been looking at film testing information too and I found this quite interesting: http://www.halfhill.com/speed1.html
and: http://www.halfhill.com/speed2.html

Steve.

timbo10ca · Feb 8, 2007

Chuck1 said:
Basic concept of the ZS:

The placement of a particular reflectance within the scene on a particular zone within the scale of zones i.e., usually from zone I to zone V. Read Fred Picker's Zone VI Workshop. It's great for someone new to ZS (get AA's "The Negative" for that matter, but I would start with Picker's book first). You do not have to find a personal film speed right off the bat to be able to use the ZS, although you should eventually become aware of what to do when your low value placements do not yield the density in the negative that you anticipate.

I recommend rating your film as per the box speed, practice with some low value shadow placements for exposure (would be best if your 35mm camera has some degree of spot metering), develop the film as per the manufacturer's recommendations. I personally would not be messing around with film testing and variable development until you have a firm grasp of the basic tenet of the ZS: i.e., the "placement" of values on the exposure scale and determining where other values "fall" (a spot meter makes such determinations easier, however).

These are just some suggestions. When I was learning the ZS, I did exactly that----I rated my film as per the box speed, developed as per recommendations for the developer I was (and still am) using. I did this until it became intuitive as to what was occurring based on my actions. Then other aspects such as plus/minus development, filtration, etc...gently fell into my understanding. I'm a 120 user and I'm getting along just fine with ZS "stuff".

Just a suggestion---good luck and regards.

Chuck

Good suggestion.

I've actually done exactly as you say, but I started off by reading the entirety of Lewis Downey's website http://www.zonesystem.com/ and practicing with his emulator. I felt I had a very good handle on the ZS, other than pre-exposure at that point. I bought and read all 3 of AA's books, and now feel that the whole ZS is quite intuitive, and I just have to practice it to get the nuances. I've been using only FP4+ with only Ilfosol S since the 1st day I developed my own film. I feel familiar enough with these products, and my ability to make a proper contact sheet to say that I am underexposing the vast majority of me shots, and I've been applying the basics of the ZS all along regarding exposure. I've been using 35mm film, and my camera has a spot meter.
I have not determined N or N- or N+ development yet, because I have only just recently come to the point that I need to start film testing. I have no access to a densitometer. My 1st film test was using Steve Simmons' technique in "Using the View Camera", but in retrospect I realize I goofed it up. I still have not tried N, N- and N+ tests yet, as I am just starting to flub my way through the whole tesing process. My film rating (flawed as it is) put the FP4+ at ISO 64, so I am almost inclined to believe it.
I'm getting to the point where I feel as though I have information overload, and just have to take a step back. There are too many ways to do the same thing, but the most accurate seem to be using a densitometer. I have an enlarging meter from RH Designs on its way, and it is supposed to allow me to do this.
Essentially I am trying to get a method figured out that I can believe in and stop questioning (I went through the same thing with the Sunny 16 Rule), as I have just aquired a 5x7 camera and don't want to be wasting a bunch of film. My BTZS book and DVD came in the mail yesterday. I will get through it (although it looks like a dry read), and probably send my LF film and paper out for testing. I will also get the Picker book because it is so highly recommended, but I've got to stop reading everything that is recommended and start doing. There must be 8 more books I've been recommended to read.
I started this thread because just when I though I understood what I was doing, this concept seemed to turn thigns on its head and I needed some clarification.

Thanks,
Tim

timbo10ca · Feb 8, 2007

Steve Smith said:
I have been looking at film testing information too and I found this quite interesting: http://www.halfhill.com/speed1.html
and: http://www.halfhill.com/speed2.html

Steve.

I will definitely look into this.

Thanks, Tim

jstraw · Feb 8, 2007

I have a film testing question.

The Massive Dev Chart has a time of 50 min for FP4+ in 510-Pyro, 1:500 @ 21c. It doesn't have a time for HP5+ in the same regime.

If the chart tells me that FP4+ and HP5+ should be developed for the same time (20 min) in some other dilute developer (it does for Rodinal 1:100, 20c) would it be a good starting point to use the same 50 min time for HP5+ for 1:500 510-Pyro?

Michel Hardy-Vallée · Feb 8, 2007

Tim, if you want a simple testing procedure that will at the same time fit your EI/dev time to your paper, try the following one:

Setup a plain target in even daylight. A big cardboard piece, say.
Meter it using the film ISO (let's say it's a 400): that's a Zone V
Close the lens cap and expose a blank frame
Open the cap and expose a series of frames from Zone 0 (closing 5 stops from meter read) until Zone X (opening 5 stops from meter read). There's a way to use only two shutter speeds and manipulate only aperture for this, let me know if you want to have it.
Process the roll under normal conditions with your chosen developer. Let's say for example that the manufacturers recommend 8 mins. Develop the roll at 8 mins.
Make a contact print using the grade you like for 35mm prints, let's say G3. The important thing is that the frame you shot with the lens cap on be a full black. Find the minimal time for it by gradually hiding the contact with an opaque card.
Now start analyzing
If the first distinct grey is on the Zone II exposure, you have a proper EI (400). If it's on Zone III, your EI is 200. If it's Zone I, your EI is 800
Count the number of greys between pure black and white. If you have seven, your dev time is OK. If you have six, that's N+. If you have eight, that's N-.
From now on, you can repeat the test a second time if you did not get a first grey on Zone II and seven greys (including Zone II).
Let's say that the first grey was Zone III, and that you had six greys. That's the likeliest result.
You're going to set your meter to 200 instead of 400, shoot the same sequence, and develop for 20% less than 8 mins (~6 mins), and do the contact sheet again.
That should get you close enough. You can do minor tweakings to nail it properly, but that's the gist of it. You would do the reciprocal process if your first grey was Zone III etc.

The whole point of film testing is to get the dev time that will fit your scene into your paper, and the EI that will maximize the speed of your film. You don't even need a densitometer, because you are using the tones on paper as a guide. It's about what's on the paper first.

All the systems you've read, whether it's "expose for the shadows, develop for the highlights," the ZS, BTZS, or Barry's heuristics, ARE ALL THE SAME DAMN THING! Everyone is using different methodologies, and have a more or less precise way of doing things, but, repeat after me, IT'S ALL THE SAME THING!

Go in peace.

timbo10ca · Feb 8, 2007

mhv said:
All the systems you've read, whether it's "expose for the shadows, develop for the highlights," the ZS, BTZS, or Barry's heuristics, ARE ALL THE SAME DAMN THING! Everyone is using different methodologies, and have a more or less precise way of doing things, but, repeat after me, IT'S ALL THE SAME THING!

Go in peace.

This piece of wisdom struck me on the way to work this morning. I understand the zone system, but I never really thought about the basis for it- if a scene is contrasty/bright, you will be overexposing it and must therefore decrease development to fit it all into your film's exposure latitude. The opposite is true for a dull scene. How you "rate" your film is just a starting point for you to keep your blacks black.

I will try your method- it is similar to the method I bungled by Steve Simmons, but I understand what it's doing. The only part I don't like about it is that it is subjective- "minimum black" and "first grey" can be too many things to my eye, and I'm trying to get as *exact* as possible so I can achieve the best negs possible for printing, which is what I perceive to be the hardest part. Exposing the neg is a calculated science, which is simple once you get the mechanics figured out.

Thanks to you once again,
Tim

timbo10ca · Feb 8, 2007

mhv said:
[*] Make a contact print using the grade you like for 35mm prints, let's say G3. The important thing is that the frame you shot with the lens cap on be a full black. Find the minimal time for it by gradually hiding the contact with an opaque card.

I assume you mean I use a piece of blank paper at a set height, do a test strip series until I see 1st pure black, and then expose the contact sheet at this time?

If the first distinct grey is on the Zone II exposure, you have a proper EI (400). If it's on Zone III, your EI is 200. If it's Zone I, your EI is 800

makes sense- if 1st grey is up at zone 3, you need more exposure time to bring it to zone 2

Count the number of greys between pure black and white. If you have seven, your dev time is OK.

you kinda lost me here, unless you are considering zone 1 and zone 9 to be pure black and white, which is what I thought zone 0 and 10 were supposed to be.

If you have six, that's N+. If you have eight, that's N-.

I'm trying to wrap my head around this one- If there are six greys when you expect seven, that's a contraction (therefore N-), is it not? Vice-versa for 8?

From now on, you can repeat the test a second time if you did not get a first grey on Zone II and seven greys (including Zone II).
Let's say that the first grey was Zone III, and that you had six greys. That's the likeliest result.
You're going to set your meter to 200 instead of 400, shoot the same sequence, and develop for 20% less than 8 mins (~6 mins), and do the contact sheet again.

You mean, repeat this test until you get your proper film speed and normal development for that speed? Suppose you determine this, how do you then determine what N+ and N- are?

I apologize if I'm misunderstanding something obvious,

Tim

Roger Hicks · Feb 8, 2007

timbo10ca said:
The only part I don't like about it is that it is subjective- "minimum black" and "first grey" can be too many things to my eye, and I'm trying to get as *exact* as possible so I can achieve the best negs possible for printing, which is what I perceive to be the hardest part. Exposing the neg is a calculated science, which is simple once you get the mechanics figured out.

Thanks to you once again,
Tim

Dear Tim,

It's ALL subjective, too. The science of exposure is nothing like as exact as most people assume, and there's a lot of latitude you can fix in the darkroom.

'First grey' is easy: if you can see it at a hard/discontinuous junction (neg density = 0.03 or above), you've got it. Going as high as 0.10 or even 0.15 will do no harm.

Not sure what you mean by 'minimum black'. Presumably the minimum exposure required to get the maximum black of which the paper is capable. If it is that, it ain't difficult either.

This won't alter the way you want to work, so in that sense it's useless, but you might care to look at 'Why we don't use the Zone System' in the Photo School at www.rogerandfrances.com, just for an additional perspective. It's free, so all it costs you as a couple of minutes of your time.

Cheers,

R.

Michel Hardy-Vallée · Feb 8, 2007

timbo10ca said:
This piece of wisdom struck me on the way to work this morning. I understand the zone system, but I never really thought about the basis for it- if a scene is contrasty/bright, you will be overexposing it and must therefore decrease development to fit it all into your film's exposure latitude. The opposite is true for a dull scene. How you "rate" your film is just a starting point for you to keep your blacks black.

I will try your method- it is similar to the method I bungled by Steve Simmons, but I understand what it's doing. The only part I don't like about it is that it is subjective- "minimum black" and "first grey" can be too many things to my eye, and I'm trying to get as *exact* as possible so I can achieve the best negs possible for printing, which is what I perceive to be the hardest part. Exposing the neg is a calculated science, which is simple once you get the mechanics figured out.

Thanks to you once again,
Tim

You're most welcome! It took me a while to figure out how each testing procedure worked, but after reading a thorough article on BTZS it dawned on me that the fundamental principles are absolutely identical.

If you want the primer on what's different beween ZS and BTZS, BTZS methodology allows you to calculate super-precisely N+0.85 or N-0.72, not just N+1 or N-1. Do you need this granularity in 35mm? I sure don't! Large format and alt process people on the other hand have probably the most exacting procedure for their exacting needs. In comparison ZS is a bit more granular than Barry's method.

You'll see that minimum time for maximum black is very easy to get. Let's say you're making a test strip by moving the card over your neg+paper sandwich. You go 4, 6, 8, 11, 16 seconds (because you understand that linear darkening demands non-linear time increases, like the f-stops on a lens or a shutter).

Suppose that 6 and 8s are distinguishable but that 8 and 11 are not. Ergo, 8s is your minimal time for maximum black.

Regarding "first grey", you'll see that the difference between black and first grey is more striking than between two adjacent greys. So you don't need very acute eyes to see it. I think the reason has to do with how film builds up density.

One last detail I have not mentioned is that when you reduce developing times, you also reduce film sensitivity a little bit. Not much, but a little bit. If you want a more precise calibration, just change one variable at a time instead of changing the two as I said in my example, and control for the constancy of the other between tests. For example, reduce development time first, and see whether your first grey falls at the same place. If it it does, you're set. If it does not, adjust your EI in consequence.

timbo10ca · Feb 8, 2007

Roger Hicks said:
Dear Tim,

It's ALL subjective, too. The science of exposure is nothing like as exact as most people assume, and there's a lot of latitude you can fix in the darkroom.

'First grey' is easy: if you can see it at a hard/discontinuous junction (neg density = 0.03 or above), you've got it. Going as high as 0.10 or even 0.15 will do no harm.

Not sure what you mean by 'minimum black'. Presumably the minimum exposure required to get the maximum black of which the paper is capable. If it is that, it ain't difficult either.

This won't alter the way you want to work, so in that sense it's useless, but you might care to look at 'Why we don't use the Zone System' in the Photo School at www.rogerandfrances.com, just for an additional perspective. It's free, so all it costs you as a couple of minutes of your time.

Cheers,

R.

Thanks Roger- I think your site is a wealth of useful information. Maybe I'm getting overly neurotic about the whole thing because I think my negs look like crap, while so many other people are getting great ones, and hammering home the importance of getting pristine negs to print. BTW- that's exactly what I meant by minimum black,

Tim

ElrodCod · Feb 8, 2007

+1 for the Picker book recommendation. He did a good job of distilling the ZS down to the bare essentials without making a religion out of it. The book offers straightforward tests for determining your "personal" film speed and developing time. A film with a box speed of 400 may need to be rated higher or lower depending on how the shutter in your camera is firing. No two cameras are alike. Don't scrimp on the testing and assume what works in one of your cameras will work in another.

Roger Hicks · Feb 8, 2007

timbo10ca said:
Maybe I'm getting overly neurotic about the whole thing because I think my negs look like crap, while so many other people are getting great ones, and hammering home the importance of getting pristine negs to print. BTW- that's exactly what I meant by minimum black,

Tim

Dear Tim,

The REALLY easy approach:

Bracket all your next roll, +/- 1 stop. Print the ones you like best(usually +1!)

If they print best on grade 2 to 3, your dev times are spot on. If you need 1 to 2 (or 0), decrease your dev time by 20%. If you need 3 to 4 (or 5), increase it by 10%.

Zero in from there on what you like best. If there's plenty of shadow detail, go up 1/3 to 2/3 stop. If they print on 2-3-4,cut dev another 5%. If they print on 1-2-3, increase it 10%. Your aim is a speed that gives you the shadow detail you want, plus a full tonal range on grade 2 or 3.

Your personal best negs might be +2/3 stop at the manufacturers' dev times, or manufacturer's ISO speed +10%, on the dev times, or something else. A lot depends on how you meter, too. With a spot meter, I use ISO box speed or box speed +1/3 (eg ISO 400>EI320). With an in-camera meter, I use anything from around box speed (overcast) to half box speed (sunny) -- though developers can influence true ISO speed from 2/3 stop faster (ISO 400>ISO 650) to a stop or more slower (ISO 400> ISO 200).

Always compare prints, Is A better than B? Go for the EI/dev time that gave you A. Reduce both EI variations (less than 1/3 stop is meaningless) and dev variations (under +10/-5% is meaningless) until you're happy.

Cheers,

R.

Michel Hardy-Vallée · Feb 8, 2007

timbo10ca said:
I assume you mean I use a piece of blank paper at a set height, do a test strip series until I see 1st pure black, and then expose the contact sheet at this time?

Yes.

timbo10ca said:
Count the number of greys between pure black and white. If you have seven, your dev time is OK.

you kinda lost me here, unless you are considering zone 1 and zone 9 to be pure black and white, which is what I thought zone 0 and 10 were supposed to be.

"Zone 1" and "Zone 9" are words for how you interpret your meter reading. If you do not interpret reading, we call it "Zone 5." In a properly calibrated system, when printed on paper, this will look like a grey card. If you augment or reduce your exposure relative to the meter reading, you will get a "zone 3" or a "zone 4" etc., depending on how many stops you add/remove from the reading. Does that make more sense?

In a properly calibrated system with N development, Zone I is still pure black. Zone 0 is just a way to say "one stop less exposure than Zone I." Likewise, Zone 9 is as white as the paper can be. Zone X is just one stop more exposure than Zone 9.

timbo10ca said:
If you have six, that's N+. If you have eight, that's N-.

I'm trying to wrap my head around this one- If there are six greys when you expect seven, that's a contraction (therefore N-), is it not? Vice-versa for 8?

Nope. Let's say you have seven frames of film corresponding to Zone II to Zone VIII exposure (see explanation above). They are all separated by one f-stop at the moment of exposure. They were "born equal" so to speak.

When you develop them, they will become seven gradually opaque frames. If your film is developped properly, the least opaque one will print dark grey on paper, and the most opaque will print light grey on paper. That's your seven grays.

Let's say you have developped for longer than you should have. What's happening is this: the least exposed frames will get a tad darker, perhaps insignificantly so. But the more exposed frames will get proportionally WAY more dark. The ration of opacity between the least and the more opaque will have augmented. The rich get richer while the poor stay put. Just like in real life.

Ergo, if you have developped too much, the more exposed frames will be too opaque, and will print as pure white on paper, while the least exposed frames will stay more or less the same. Instead of having seven grays, you will have six or five.

timbo10ca said:
From now on, you can repeat the test a second time if you did not get a first grey on Zone II and seven greys (including Zone II).
Let's say that the first grey was Zone III, and that you had six greys. That's the likeliest result.
You're going to set your meter to 200 instead of 400, shoot the same sequence, and develop for 20% less than 8 mins (~6 mins), and do the contact sheet again.

You mean, repeat this test until you get your proper film speed and normal development for that speed? Suppose you determine this, how do you then determine what N+ and N- are?

Yes. N+ is a pair (dev time; EI), N- is a pair (dev time; EI). For example, my N is (6 mins; 200), my N+ is (8 mins; 400) and my N- is (4 mins; 100).

My N means:
* My meter is set at 200
* The frame that I expose at Zone II is the first grey on the contact
* I have 7 distinct greys (zone II to zone VIII) on the contact

My N+ means:
* My meter is set at 400
* The frame that I expose at Zone II is the first grey on the contact
* I have 6 distinct greys (zone II to zone VII) on the contact

My N- means:
* My meter is set at 100
* The frame that I expose at Zone II is the first grey on the contact
* I have 8 distinct greys (zone II to zone IX) on the contact

I hope I'm not making this more complicated for you!

timbo10ca · Feb 8, 2007

mhv said:
Yes.

"Zone 1" and "Zone 9" are words for how you interpret your meter reading. If you do not interpret reading, we call it "Zone 5." In a properly calibrated system, when printed on paper, this will look like a grey card. If you augment or reduce your exposure relative to the meter reading, you will get a "zone 3" or a "zone 4" etc., depending on how many stops you add/remove from the reading. Does that make more sense?

In a properly calibrated system with N development, Zone I is still pure black. Zone 0 is just a way to say "one stop less exposure than Zone I." Likewise, Zone 9 is as white as the paper can be. Zone X is just one stop more exposure than Zone 9.

Nope. Let's say you have seven frames of film corresponding to Zone II to Zone VIII exposure (see explanation above). They are all separated by one f-stop at the moment of exposure. They were "born equal" so to speak.

When you develop them, they will become seven gradually opaque frames. If your film is developped properly, the least opaque one will print dark grey on paper, and the most opaque will print light grey on paper. That's your seven grays.

Let's say you have developped for longer than you should have. What's happening is this: the least exposed frames will get a tad darker, perhaps insignificantly so. But the more exposed frames will get proportionally WAY more dark. The ration of opacity between the least and the more opaque will have augmented. The rich get richer while the poor stay put. Just like in real life.

Ergo, if you have developped too much, the more exposed frames will be too opaque, and will print as pure white on paper, while the least exposed frames will stay more or less the same. Instead of having seven grays, you will have six or five.

Yes. N+ is a pair (dev time; EI), N- is a pair (dev time; EI). For example, my N is (6 mins; 200), my N+ is (8 mins; 400) and my N- is (4 mins; 100).

My N means:
* My meter is set at 200
* The frame that I expose at Zone II is the first grey on the contact
* I have 7 distinct greys (zone II to zone VIII) on the contact

My N+ means:
* My meter is set at 400
* The frame that I expose at Zone II is the first grey on the contact
* I have 6 distinct greys (zone II to zone VII) on the contact

My N- means:
* My meter is set at 100
* The frame that I expose at Zone II is the first grey on the contact
* I have 8 distinct greys (zone II to zone IX) on the contact

I hope I'm not making this more complicated for you!

This is becoming more and more clear to me- thanks alot. I'm just wondering how you are making these N, N-, and N+ pairs. By increasing one variable and decreasing the other, doesn't the outcome stay equal (I'm thinking in linear relationships here to keep it simple in my mind). I thought your N+ and N- were development times you applied to a single, unchaging EI/film iso rating.
Also, what is the f/stop and time combo you mentioned earlier for the test frames?

Thanks,
Tim

Ray Heath · Feb 8, 2007

timbo10ca said:
I am in the process of trying to do some film tests according to the Zone System in 35mm. I think understand the concept - Find the correct film speed that gives you detail in Zone 3, then find the development time that gives you good detail in Zone 8. Then it all got turned on its ear when I was reading a thread at P.net and someone mentioned Barry Thornton's "Edge Of Darkness". He sais that for depending on the brightness of the scene, rate the film at box ISO (cloudy, no shadows) and develop as recommended, and to rate the film at 1/2 box iso and decrease development by something like 20-30% (bright sun, sharp shadows). I thought that film testing was to give you the film's speed, regardless of the light outside! Is his vernacular just another way of deciding on exposure and N minus development for scenes that have a long exposure gradient for "non-zonies"? I'm trying to wrap my head around his use of box ISO for cloudy scenes and normal development though. It seems that film is always slower than its box ISO.....

Thanks again,
Tim

i have read some of this 'high tech' stuff on exposure, they make it unnecessarily complicated especially for negative exposure

but i know from experience box iso is probably calculated for nice soft light, so if my subject and scene is illuminated by soft light (not often outdoors in Australia) then i set manufacturers recommended ISO (who am i to argue with the experts) and process as recommended with a 'normal' developer

if my lighting situation is contrasty i set half ISO and reduce dev time by 30%

in all cases i meter off something middish toned that is getting the same light as my subject/focal point and use that setting

it doesn't have to be rocket science, making it complicated and high tech doesn't make it better

Michel Hardy-Vallée · Feb 8, 2007

timbo10ca said:
This is becoming more and more clear to me- thanks alot. I'm just wondering how you are making these N, N-, and N+ pairs. By increasing one variable and decreasing the other, doesn't the outcome stay equal (I'm thinking in linear relationships here to keep it simple in my mind). I thought your N+ and N- were development times you applied to a single, unchaging EI/film iso rating.
Also, what is the f/stop and time combo you mentioned earlier for the test frames?

Thanks,
Tim

Tim, the first thing to understand about film testing is that nothing is linear. Development effects densities unequally. You're always doubling or halving the quantity of light. There is a discrete step between unexposed film and minimal exposure, not a continuous one, etc.

If you increase exposure and reduce development, that's not doing the same thing as reducing exposure and increasing development. The reason lies in the fact that development impacts highlights in a different way than it impacts the shadows.

The nature of the reaction of photosensitive emulsions (film and paper) to light is the single most fundamental thing to grasp. It's because of its characteristics that what seems to be equivalent operations are not. You should probably get some graphics of a characteristic curve to help you.

At this point, I guess if you want to know the WHY rather than the HOW, you need to get a textbook like Ansel Adam's The Negative (the last editions are way more readable than the earlier ones).

The reason why the EI is different between the N, N+ and N- is twofold: first, because development also effects slightly film speed, as I've said in an earlier post. But that's just a minor correction, sometimes half to a third of a stop. The real reason is because that's how you control the contrast.

Let's say you have a scene. A portrait in the sun, light diffused from a lightly overcast sky. The light comes from the left side of your subject. Her left side is brighter than her right side because of this. You meter her left side and her right side. There's a difference of one stop. If you expose and develop your film normally, there will be a difference of one stop on the final print. You have exposed and processed for N, and thus you did not alter the contrast of the scene.

Let's say you expose it less than in the previous case. What it does is that overall, the photo will be darker, right? You have slightly underexposed. Both sides will be darker, but will bear the same relationship to each other: one stop of difference.

But let's say that on top of that you develop more. THAT's where the magic begins. The darker side will stay dark, but the brighter side will be three stops brighter than the darker side on the negative, and on the print you will also see this difference. You will have a portrait with more contrast. You have exposed and developed for N+, and you have augmented the contrast of the scene.

Steve Smith · Feb 9, 2007

Roger Hicks said:
The science of exposure is nothing like as exact as most people assume, and there's a lot of latitude you can fix in the darkroom.

Whilst I agree with this, generally it seems that in camera exposure is seen as an exact science whereas darkroom exposure is seen as more of an art when, in fact, both should be equally predictable.

I am going to do an experiment the next time I am in the darkroom (hopefully this weekend).

I am going to select a negative then put it in the enlarger and compose and focus it. Then I am going to remove the negative and replace it with a blank piece of film from the same roll and do a test strip to find minimum time for maximum black.

I will then replace the negative and expose for this time. If the negative was exposed and processed correctly, I should have a good print (assuming grade 2 to 3 filtration).

If it is too dark, then the natural instinct to reduce the exposure time will obviously not work as I would not then get maximum black. An increase in grade will be required.

I will post my results if they are of any interest.

Steve.

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