Plus/minus development guidelines
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).
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.
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.
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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...
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.
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.
Last edited by Sirius Glass; 09-19-2015 at 06:08 PM. Click to view previous post history.
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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.
An old dog learning new tricks
It's a loose std and results depend on materials but a full film test will give you the proper times for your combinations
Originally Posted by M Carter
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.
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.