Plus/minus development guidelines

M Carter · Sep 19, 2015

I've been reading everything I can get my hands on, but still unclear on something:

I understand metering a scene to find the contrast range, and then deciding on, say, N+1 or N+2 development. But are there any solid guidelines for what each "plus" is?

For instance, I'll read that +1 is 15%, or 20%, or 25% longer development - so is this just a loose standard?

And is there any real-world alignment between, say, a plus-one and how many grades of contrast increase can be expected? (Though I assume this varies across films and developers).

++++++ (backstory)+++++++

I have been trying to get a good negative of a small bromoil print so I can reprint it larger (and on liquid emulsion on canvas, so I need a neg for grade 3, the emulsion is fixed grade).
The print is very flat - it metered just three stops from darkest shadows to whitest white (I couldn't really get the damn whites to clear in the bromoil session).

I shot it with Pan-F Plus (120 film, 6x7 negs) but really couldn't develop for more contrast (I've heard that film described as a "Straight jacket" as far as tweaking contrast); I re-shot it with FP4+ (120 again), metered for the shadows, bracketed 3, repeated for all 10 frames, snipped a third of the roll and doubled the development time (4:30 called for at 1:31 HC110, did it for 8 minutes). I don't own a densitometer but it looks like I got a great neg that way - much more contrast and should give me some snappy highlights and deep shadows with plenty of detail.

I snipped the rest of the film in half and also dev'd at 12 and 16 minutes, just to see what happened. 12 also gave me a snappy neg with hotter highlights (not plugged up), and 16 made the next-darkest bracket come very close to the optimal bracket in the first run, but less density in shadow areas. So I have several negs to test for optimal look at a fixed paper grade, I call it a success. But I'm a little amazed at how hard I blasted that film with chemistry to break out of the 3-stop rut of the original.

Does one need to run these sorts of tests with their films of choice to suss out just what N+1, N+2, and so on actually are?

I do enjoy the testing, it's nice to see how things work vs. read about it I suppose.

RobC · Sep 19, 2015

Why don't you use a lot more light on the bromoil print which should give it a lot more contrast to start with. That way, if you can get enough contrast from it, you won't need to alter dev. Two flash units, one either side at 45 deg to the print.

N+ development needs to be calibrated to see if your're really getting what you're expecting. Hence the ball park figures people throw out.

M Carter · Sep 19, 2015

I shot the mounted print with two speedotron heads in medium photoflex softboxes at the correct angles and equal distances - identical heads and softboxes (I spent my teen years running a stat camera, so I know how to do copy work).

Blasting the print with more light would just move my exposure around - it won't change the tonal values of the print.

With the demise of Foma 123, I'm having trouble finding a good bromoil paper that gives the contrast I want - the highlights hold more ink than they should. Still trying different papers. But that's another story...

Alan9940 · Sep 19, 2015

First, not all modern emulsions expand as easily as we may like nor expand to values that we may need. I don't use TMax films, but over the years I've heard that their N+ development capability is pretty good. The way I learned expansion development was that you have to begin with a calibrated N development time yielding a Zone VIII density when paper is exposed for the minimum time to reach maximum black. Then, expose a negative to Zone VII and develop for whatever time is necessary to reach Zone VIII density using all the same parameters as for your N development testing. This is your N+1 development time. Repeat for N+2 by exposing a negative to Zone VI and developing long enough to reach Zone VIII. Rinse, repeat.

I'm sure those with densitometers can probably gather this data much faster than what I've described and there are many details not covered in that short paragraph above. As you can probably tell and as RobC said, it all takes calibration through testing. Grab a copy of Ansel's "The Negative" or Picker's "Zone VI Workshop" and you'll find a lot of what you need to know therein.

Have fun!

Sirius Glass · Sep 19, 2015

For development the +- 10% or +-15% for each f/stop [N+1 ... development] adjustment is a function of the developer. As I recall XTOL uses +-15% but another developer will be different.

RobC · Sep 19, 2015

I thought a 3 stop range across the print is really quite low so guessed (incorrectly) that you had not given it enough light.

N+1 is supposed to move zone 8 to zone 9. You haven't got a zone 8 to start with unless you expose for the highlights but then you won't have a zone 3. I think your bracketing was the right way to go in this scenario with such a short SBR.
You really need to do some serious testing to get a handle on N + or - development and a densitometer makes life a lot easier once you know what densities you are targetting. (saves on doing print tests). Read Adams "The Negative" for full explanation if you haven't already.

RalphLambrecht · Sep 19, 2015

M Carter said:
I've been reading everything I can get my hands on, but still unclear on something:

I understand metering a scene to find the contrast range, and then deciding on, say, N+1 or N+2 development. But are there any solid guidelines for what each "plus" is?

For instance, I'll read that +1 is 15%, or 20%, or 25% longer development - so is this just a loose standard?

And is there any real-world alignment between, say, a plus-one and how many grades of contrast increase can be expected? (Though I assume this varies across films and developers).

++++++ (backstory)+++++++

I have been trying to get a good negative of a small bromoil print so I can reprint it larger (and on liquid emulsion on canvas, so I need a neg for grade 3, the emulsion is fixed grade).
The print is very flat - it metered just three stops from darkest shadows to whitest white (I couldn't really get the damn whites to clear in the bromoil session).

I shot it with Pan-F Plus (120 film, 6x7 negs) but really couldn't develop for more contrast (I've heard that film described as a "Straight jacket" as far as tweaking contrast); I re-shot it with FP4+ (120 again), metered for the shadows, bracketed 3, repeated for all 10 frames, snipped a third of the roll and doubled the development time (4:30 called for at 1:31 HC110, did it for 8 minutes). I don't own a densitometer but it looks like I got a great neg that way - much more contrast and should give me some snappy highlights and deep shadows with plenty of detail.

I snipped the rest of the film in half and also dev'd at 12 and 16 minutes, just to see what happened. 12 also gave me a snappy neg with hotter highlights (not plugged up), and 16 made the next-darkest bracket come very close to the optimal bracket in the first run, but less density in shadow areas. So I have several negs to test for optimal look at a fixed paper grade, I call it a success. But I'm a little amazed at how hard I blasted that film with chemistry to break out of the 3-stop rut of the original.

Does one need to run these sorts of tests with their films of choice to suss out just what N+1, N+2, and so on actually are?

I do enjoy the testing, it's nice to see how things work vs. read about it I suppose.

It's a loose std and results depend on materials but a full film test will give you the proper times for your combinations

Stephen Benskin · Sep 19, 2015

I recommend studying Ralph's attachment. Different films will react differently in different developers. Some increase contrast faster than others, so using a percentage of development for plus or minus development is little more than a generalization. The degree of development is based on the desired end result, and that is usually a desired paper grade and method of printing. A grade 2 paper with a diffusion enlarger has a log exposure range of 1.05. A normal range scene has a luminance range of 7 1/3 stops or log 2.20. Average flare is 0.40. The equation to find the desired film gradient is:

Paper LER / Log Subject Luminance Range - Flare

Normal Development is:
1.05 / 2.2 - 0.40 = 0.58

For a 6 1/3 stop luminance range (+1) substitute 1.90 for 2.20 which gives you an aim gradient of 0.70 for +1. This is also a slight simplification because flare tends to change with changes in the luminance range, generally 0.10 per stop.

Here are two developmental charts. One using a fixed flare value (Kodak) and the other is one I call the practical flare model.

Bill Burk · Sep 19, 2015

If you found yourself thinking this is an N+2 scenario... I translate N+2 on Grade 3 paper as requiring contrast index of 0.80

This is a pretty high contrast, and it will require a lot of developing time.

For me, it takes 17 minutes in D-76 1:1 to hit near that with TMAX 100. At that point, I'd switch to D-76 straight and it would bring the time down to 12 minutes.

But you might need N+3 to fit Grade 3 paper, and that requires a contrast index of 1.1

For me, D-76 straight for 36 minutes gets me there (again TMAX 100 for me).

Good luck if you really need to call it N+4, you are probably approaching gamma infinity (the most contrast you can get from a film/developer combination).

So, yes you do need to develop film very long when you take a copy shot of a fairly low contrast original

If you can find a Time/Gamma chart relevant to your film/developer combination, and you find that you hit some points on that Time/Gamma chart reasonably closely... Then you don't have to do all that testing. You can take the manufacturer's (or friends) Time/Gamma chart and work out the necessary development times for any situation.

Bill Burk · Sep 19, 2015

p.s. I use the charts Stephen Benskin just posted.

In the practical flare model, you can find N+4

3 stops subject would be N+4, the far-right column. Grade 3 would be 0.88 on the LER row (say 0.90), the far right contrast figure for that row is 1.46

For me, 48 minutes in D-76 straight gives me 1.2 - so I still cannot reach what is really needed for the shot.

Doremus Scudder · Sep 20, 2015

As Ralph, Steven and Bill point out, testing (with your materials) is the only way to nail down exactly what you need for expansion (N+) and contraction (N-) development times (N as well!).

Keep in mind, though, that in real life even the best are pretty happy to get within a paper-grade of their goal when using the Zone System. Almost always one needs to make adjustments while printing.

Your situation is a bit different: you are copying. If I were you, I'd shoot four or five negatives of your print and develop each to different contrast indexes. Then, using your liquid emulsion in small amounts on another surface (i.e., making your own test strips) and using the same magnification you will print the final print at, print your negatives and find out which one will suit your purposes best (or, you may find you have to go back and shoot a few more...).

When I was doing copy work, I spent a lot of time narrowing down the parameters of correct copy film, exposure, development and printing paper so as to best match an original. Once that was done, I could just crank them out, but it took some time...

Best,

Doremus

Stephen Benskin · Sep 20, 2015

Copy work is different. You want to reproduce the tones of the original. If the original is flat, then the reproduction should be flat. You basically want a normal negative. The problem with copying is flare. Kodak's copy film had a uniquely shaped curve to compensate for the compression. Copying with general pictorial film might require a mask. I've also seen bleaching the highlights, but that's with silver prints. Of course, flare is introduced by the enlarger which you will probably not be using.

Since you are working with an alternative process, you will need to find the specifics for a normal negative for that process. If the grade equivalent is a grade 3, the aim negative density range is around 0.88 from 7 stop subject. While the original isn't, you are not looking to pull out the flat range of the print but to reproduce it. Since the print will be contacted and it is a copy process, flare can basically be eliminated from the equation.

0.88 / 2.1 = 0.42

or reduced flare

0.88 / 2.1 - 0.1 = 0.44

This might be a good starting place to begin testing. When I was testing Kodak's copy film, I shot and printed a gray scale. Because of the shape of the film curve, exposure had a large influence on tonal reproduction.

ic-racer · Sep 20, 2015

I shot it with Pan-F Plus (120 film, 6x7 negs) but really couldn't develop for more contrast

Get a timer that times longer or heat up the developer.

Bill Burk · Sep 20, 2015

Stephen Benskin said:
Copy work is different. You want to reproduce the tones of the original. If the original is flat, then the reproduction should be flat. You basically want a normal negative. The problem with copying is flare. Kodak's copy film had a uniquely shaped curve to compensate for the compression. Copying with general pictorial film might require a mask. I've also seen bleaching the highlights, but that's with silver prints. Of course, flare is introduced by the enlarger which you will probably not be using.

Since you are working with an alternative process, you will need to find the specifics for a normal negative for that process. If the grade equivalent is a grade 3, the aim negative density range is around 0.88 from 7 stop subject. While the original isn't, you are not looking to pull out the flat range of the print but to reproduce it. Since the print will be contacted and it is a copy process, flare can basically be eliminated from the equation.

0.88 / 2.1 = 0.42

or reduced flare

0.88 / 2.1 - 0.1 = 0.44

This might be a good starting place to begin testing. When I was testing Kodak's copy film, I shot and printed a gray scale. Because of the shape of the film curve, exposure had a large influence on tonal reproduction.

I was wondering whether the 2 stops of shaded subject region should be counted when doing copying, thus should you take 7 stops = Normal same as for pictorial work? Or if you should take 5 stops = Normal because flat copy is only able to reflect a 5 stops subject luminance range (ignoring specular reflection).

Then in part of the backstory, M Carter explained the reason for copying is to increase the contrast.

I think M Carter should aim close to gamma infinity

Stephen Benskin · Sep 20, 2015

Bill Burk said:
I was wondering whether the 2 stops of shaded subject region should be counted when doing copying, thus should you take 7 stops = Normal same as for pictorial work? Or if you should take 5 stops = Normal because flat copy is only able to reflect a 5 stops subject luminance range (ignoring specular reflection).

Then in part of the backstory, M Carter explained the reason for copying is to increase the contrast.

I think M Carter should aim close to gamma infinity

My thought was that the OP may not be going in the right direction when it comes to copying. There's a chance the reason why his results don't look good is because the image doesn't want to go in the direction he's taking it. If problem is just about contrast, the question has been answered. If it's about a copy film choice, try TMX in Xtol. There could be something else going on. Maybe the problem would be easier to identify if the OP could upload an image of the original and one of the tests.

I'm wondering where's the original negative? What about making an enlarged copy negative? It has more information to work with and has the added advantage of not having to deal with paper texture and the paper curve. Is there something going on with the printing process? Bromoil is an alternate process so it might be a good idea to also post the question in the Alternate Process forum.

M Carter · Sep 20, 2015

Thanks guys -

Regarding the original, just think of it as a "one of a kind, low contrast image" vs. something I'd go and reproduce. Getting my bromoils back to a better contrast range will involve testing more papers, technique, etc.

But meanwhile, I'm using this image to rough out other steps of the full process - getting decent size bromoil prints reproduced on large canvas, without using a computer or scanner.

For now, it's a success as far as my original post. Though my technique was a little bit of a shotgun approach (bracket exposure and guess at dev. times), I did some test prints of the new negs today and I have several contrast levels to choose from, with differences from subtle to extreme.

This wouldn't be optimal for, say, a one-day shoot with models and so on, but for copying, where I can leave the setup and go back and adjust, it's a good start, though I want to make my guesses a little more educated, at the least.

I can add one thing - finding a way to fairly precisely snip a roll of 120 film has helped me get a lot of variables tested with just one roll.

I'm hoping to get a 4x5 enlarger this fall (I have a nice cambo camera and used to shoot LF E6 to pay the rent) and moving to 4x5 for this part of the process should be a huge help.

Plus/minus development guidelines

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