from the height of my ignorance: dev time and density

pierods · Mar 14, 2009

Hello,

I am posting this in the hope of being corrected.

Please correct as you see fit. I haven't been able to find a book describing this so I am writing it down as I understand it from forums etc.

The more I expose film, the more the silver crystals absorb light.

When I pour developer onto film, it "oxidates" more the crystals that have taken more light (highlights) and it "oxidates" less the crystals that have taken less light (shadows).

The shadows (less light) oxidate less, and they oxidate first, i.e. shadows develop first, maybe in the first two minutes.

When I pour in the fixer, it eats away crystals that have not seen any light (un-oxidated), it eats the shadows, and it eats much less the highlights, because oxidated crystals are more "protected" from fixer.

This is why highlights are fat slabs of crystals and shadows are thin slabs of crystals.

If I cut development short, highlights don't get very oxidated and so the fixer will eat at them more, generating an overall thinner negative. Contrast will be low.

If I lenghten development, highlights will develop completely and I will get a contrasty fat neg.

If I overexpose my film, I will get a fatter, more contrasty negative.

The purpose of over-exposing and under-developing is to get full detail in the shadows and to keep highlights under control. The compressed highlights can be taken care of by dodging them.

Anscojohn · Mar 14, 2009

pierods said:
Hello,

I am posting this in the hope of being corrected.

If I lenghten development, highlights will develop completely and I will get a contrasty fat neg.
********
Contrasty, not necessarilly a heavy neg; depending on exposure.

If I overexpose my film, I will get a fatter, more contrasty negative.
******
You'll get a heavier negative; contrast will (all things being equal--which they rarely are) be about normal.

The purpose of over-exposing and under-developing is to get full detail in the shadows and to keep highlights under control.
******
Exactly. You have it.

The compressed highlights can be taken care of by dodging them.
*****
Yes. Or using a higher contrast paper; or higher contrast paper developer; or whistling in the dark and doing incantations.
*******
As the Professor said in My Fair Lady (sorta). "I think he's got it!"

Anscojohn · Mar 14, 2009

By the way, I solve many of the problems simply by giving generous exposure (1/2 box speed) and develop in a "semi-compensating" developer: D23. With such a developer, the highlights are partially "self-limiting" because the only developing agent in D23 (metol) is very sensitive to the restraining action of bromide. And, as you have grasped, the highlights develop more easily than the shadows because the silver grains have been more destabilized by having been exposed to more light--so they develop more readily and quickly and (with D23) immediately begin self-limiting themselves by liberating more bromide into the developing solution which is right next to those highlight images. Dilute Rodinal (1:65, 1:75, 1:85) tends to do the same thing. D23 is the lazy person's way to easily printable negatives, methinks.

Pinholemaster · Mar 14, 2009

You expose for the film shadow density, and develop for the contrast.

An overexposed negative doesn't get more contrasty, in fact it gets a flatter contrast curve because you've pushed so many zones into one or two highlight areas.

Fixer eats nothing. It simply removes what the developer doesn't develop. In the end you are left with silver in emulsion. There are no slabs. Think clumps of silver. Highlights have bigger, fuller clumps. Shadows have smaller, more dispersed clumps.

The best solution is to correctly expose, and correctly develop. Saves you tons of time in the darkroom attempting to print an overexposed, underdeveloped image.

pierods · Mar 14, 2009

Pinholemaster said:
You expose for the film shadow density, and develop for the contrast.

An overexposed negative doesn't get more contrasty, in fact it gets a flatter contrast curve because you've pushed so many zones into one or two highlight areas.

Fixer eats nothing. It simply removes what the developer doesn't develop. In the end you are left with silver in emulsion. There are no slabs. Think clumps of silver. Highlights have bigger, fuller clumps. Shadows have smaller, more dispersed clumps.

The best solution is to correctly expose, and correctly develop. Saves you tons of time in the darkroom attempting to print an overexposed, underdeveloped image.

Well, yes, correctly expose and develop, but I scan, and the scanner is picking up too much grain.

So I am trying to find out whether I need a fat or a thin neg for the scanner not to pick up grain, being that phothoshop can fix contrast.

Photo Engineer · Mar 14, 2009

Well, firstoff the work being done is reducing silver halide to silver metal. Oxidation is not involved. Second, you are left with silver in gelatin after fixing, as there is no emulsion left then.

But, as to the big question, remember that the shadows are the light part in the negative which are the coarser grains (faster speed grains), and the highlights are the dark part (all of the slow + fast grains). For this reason grain follows a somewhat bell shaped curve going from low to high and back to low. At low density, grain is low, then it rises as you get many specks of silver and then it falls as density rises and you get all of the blank spaces filled in with silver. So, even though many companies report grain as a single figure it is a continuous curve that mates with the characteristic curve.

PE

pierods · Mar 14, 2009

Anscojohn said:
By the way, I solve many of the problems simply by giving generous exposure (1/2 box speed) and develop in a "semi-compensating" developer: D23. With such a developer, the highlights are partially "self-limiting" because the only developing agent in D23 (metol) is very sensitive to the restraining action of bromide. And, as you have grasped, the highlights develop more easily than the shadows because the silver grains have been more destabilized by having been exposed to more light--so they develop more readily and quickly and (with D23) immediately begin self-limiting themselves by liberating more bromide into the developing solution which is right next to those highlight images. Dilute Rodinal (1:65, 1:75, 1:85) tends to do the same thing. D23 is the lazy person's way to easily printable negatives, methinks.

Divided or not?

pierods · Mar 14, 2009

Photo Engineer said:
Well, firstoff the work being done is reducing silver halide to silver metal. Oxidation is not involved. Second, you are left with silver in gelatin after fixing, as there is no emulsion left then.

But, as to the big question, remember that the shadows are the light part in the negative which are the coarser grains (faster speed grains), and the highlights are the dark part (all of the slow + fast grains). For this reason grain follows a somewhat bell shaped curve going from low to high and back to low. At low density, grain is low, then it rises as you get many specks of silver and then it falls as density rises and you get all of the blank spaces filled in with silver. So, even though many companies report grain as a single figure it is a continuous curve that mates with the characteristic curve.

PE

So you are saying that the shadows are necessarily grainier? And if so, what could be done to make them less grainy, if contrast is not a problem (I scan)? Would the answer be "turn them into semi-highlights by giving them more exposure so they are made of more small grains (slower fast grains)? And the consequence of this would be a compressed neg?

Anscojohn · Mar 14, 2009

pierods said:
Well, yes, correctly expose and develop, but I scan, and the scanner is picking up too much grain.

So I am trying to find out whether I need a fat or a thin neg for the scanner not to pick up grain, being that phothoshop can fix contrast.

******
Pierods,
I have developed film and made prints for almost fifty years. What I said to you has to do with that about which I feel I know a little bit. Scanning is something which is terra incognita for me.

pierods · Mar 14, 2009

Anscojohn said:
******
Pierods,
I have developed film and made prints for almost fifty years. What I said to you has to do with that about which I feel I know a little bit. Scanning is something which is terra incognita for me.

Not a problem, I'll work that out. Is your d23 divided or not divided?

dancqu · Mar 14, 2009

Photo Engineer said:
Well, firstoff the work being done is reducing silver halide
to silver metal. Oxidation is not involved. Second, you are
left with silver in gelatin after fixing, .... PE

The OP should seek for another source for his information.
Perhaps he is reading from the same source I read from
several years ago. According to that source the alkali's
ONLY reason for being in the developer is the
swelling of the gelatin. Dan

Photo Engineer · Mar 14, 2009

Dan;

There are so many errors being circulated on the internet and being written in books about photographic science that it astounds me!

PE

drazak · Mar 14, 2009

Dan, Pierods;

SIlver halides are light sensitive and are suspended in gelatin, without sensitizing dyes and whatnot, when light hits them they are reduced, IE. gaining electrons, however they are not very reduced. The developer reduces those halides and some that were not exposed to light (the fog). The reduction of silver halides to elemental silver (the blacks on film and paper) produces hydronium ions, which are what makes a solution acidic, this is what the alkali is in the developer to nullify, as the concentration of hydronium ions in a area increases, rate of development decreases. The alkali in the developer reacts with hydronium ions to create water, which is 'neutral'. Fixer removes the unreduced silver halides, forming a complex with them and carrying them away, as the complex is water soluble, the silver halides are quite definitely not soluble, having solubilities in completely pure water of something like .0000014 grams per litre, not very large, however the solubilities of silver haldide complexes with fixer are very large(the solubilities of the other silver halides used in photography are fairly similar). The reason you have to wash your film very well or use a two fixer bath, or any of the hypo clearing agents is not that you must remove the fixer, it is that you have to remove some of the silver complexes and byproducts of them that are formed that are not removed in stagnant water. The only thing that is oxidized in film and paper development are the developing agents, and their becoming oxidized is what produces the hydronium ions, as stated before. As PE mentioned, the grain distributes itself in a gausian way, the most grain will be in midtones, not in shadows or hilights.

I hope this helped you better understand the photographic process.

Ben

Anscojohn · Mar 14, 2009

pierods said:
Divided or not?

*******
I have tried divided. I see nothing at all to merit the additional hassle. I have been using D23 almost exclusively since about 1975.

srs5694 · Mar 14, 2009

pierods said:
Well, yes, correctly expose and develop, but I scan, and the scanner is picking up too much grain.

So I am trying to find out whether I need a fat or a thin neg for the scanner not to pick up grain, being that phothoshop can fix contrast.

Scanning is a touchy subject around here, and if you need scanner-specific advice, you may want to try on Hybrid Photo, this site's sister site. There certainly are scanner-specific things you can try, like grain-reduction algorithms in some scanner software.

That said, the principles you're asking about are the same whether you scan or print traditionally. One comment I have is that you might want to give Ilford XP2 Super and/or Kodak BW400CN a try. These are "chromogenic" B&W films, which are processed in C-41 chemistry just like color print films. They might be of interest for a couple of reasons. First, they tend to be rather fine-grained, and their "grain" (after processing) is in fact dye clouds, just like in color films. This produces a different look to the grain, and you may find that look preferable to conventional films. Second, the chromogenic films often scan better than traditional B&W films. In my experience, the grain tends to be exaggerated less with chromogenics than with traditional B&W films, and it's possible to use the "digital ICE" feature of many scanners on these films. (This feature doesn't work with traditional B&W films.)

This isn't to say that chromogenic films are "silver bullets," but if you haven't tried them, they are worth trying, particularly if you dislike the grain you're seeing with traditional films.

Another point/question: What films are you using? Slower films are, generally speaking, finer-grained than faster films. (Both the chromogenic B&W films are ISO 400 products.) T-grain films (Kodak T-Max, Ilford Delta, and Fuji Acros) are finer-grained than other B&W films of similar speed, and the grain in T-grain films has a different overall look. Thus, you might want to try a slower film and/or switch from conventional to T-grain.

These suggestions are all "shots in the dark," since I don't know what materials you're using now or precisely what you want to achieve. I thought I'd toss them out there, though, in case you didn't know these things or hadn't considered them.

pierods · Mar 15, 2009

Scanning is a touchy subject around here, and if you need scanner-specific advice, you may want to try on Hybrid Photo, this site's sister site.

==> true, but you people know so much more about film than us hybrids (us mutts?) that sometimes we need to come back to the source...

There certainly are scanner-specific things you can try, like grain-reduction algorithms in some scanner software.

==> I have noticed that with b/w films, scanner software tends to choke on just about anything that is not simple scanning

That said, the principles you're asking about are the same whether you scan or print traditionally. One comment I have is that you might want to give Ilford XP2 Super and/or Kodak BW400CN a try. These are "chromogenic" B&W films, which are processed in C-41 chemistry just like color print films. They might be of interest for a couple of reasons. First, they tend to be rather fine-grained, and their "grain" (after processing) is in fact dye clouds, just like in color films. This produces a different look to the grain, and you may find that look preferable to conventional films. Second, the chromogenic films often scan better than traditional B&W films. In my experience, the grain tends to be exaggerated less with chromogenics than with traditional B&W films, and it's possible to use the "digital ICE" feature of many scanners on these films. (This feature doesn't work with traditional B&W films.)

This isn't to say that chromogenic films are "silver bullets," but if you haven't tried them, they are worth trying, particularly if you dislike the grain you're seeing with traditional films.

==> I have noticed that the look of chromogenics is almost exactly the look of digital b/w, which I don't like

Another point/question: What films are you using? Slower films are, generally speaking, finer-grained than faster films.

==> when I scan rollei ortho 25, everything is hunky dory...

(Both the chromogenic B&W films are ISO 400 products.) T-grain films (Kodak T-Max, Ilford Delta, and Fuji Acros) are finer-grained than other B&W films of similar speed, and the grain in T-grain films has a different overall look. Thus, you might want to try a slower film and/or switch from conventional to T-grain.

==> I have not been able to reproduce the wonderful tones of classic grain on t-grain films. I know Kodak says you can, but I couldn't...

These suggestions are all "shots in the dark," since I don't know what materials you're using now or precisely what you want to achieve. I thought I'd toss them out there, though, in case you didn't know these things or hadn't considered them.

Thanks for all the info. I tried to keep everything strictly analogic by restraining myself to asking questions about neg thickness and grain size.

edtbjon · Mar 15, 2009

Pierods, you didn't say what format you are shooting, so let's assume 35mm. In that case I can recommend using shorter pieces of film (e.g. by bulk loading) so that you can use one roll of film for a given subject or series of similar subjects. (This is one of the reasons why I like shooting 6x6 on 120 film, 12 exposures.) Now, why?
Then you can adjust the development to suit that particular scene and thus minimize the overall grain, i.e. not getting more grain than neccessary for whatever you are shooting. In some scenes, you will need to press on a bit, so you will get grain, but also easily printable negatives. (In your case, negs which will still scan nicely, just with a bit more grain.)
In general, for scanning, try to adjust dev. times to something a little bit shorter than that for condenser enlargement. Apart from that, you have already gotten all the advice you can get from the knowledgeable expertize on this forum.

//Björn

pierods · Mar 15, 2009

And I thank everybody for chipping in.

Anscojohn · Mar 15, 2009

pierods said:
And I thank everybody for chipping in.

******
You are welcome: now trash that scanner and head for the darkroom!!!

ghost · Mar 15, 2009

Anscojohn said:
******
You are welcome: now trash that scanner and head for the darkroom!!!

pierods · Mar 15, 2009

I know, I know...i gotta do that...

But next year I'm going pro, and you know how it is, they'll want digital.

But in the background, I will NEVER give up my tri-x and hp5 and ortho25, and when I'll be able to dictate what my customers must accept, I WILL trash that contraption.

People have no idea...sometimes, just for fun, I go around with this:

http://www.amazon.com/Hurrells-Holl...bs_sr_1?ie=UTF8&s=books&qid=1237150896&sr=8-1

and I ask people, is digital better than film, and they invariably say "of course", then I start browsing the book in front of them, and I start hearing the "aaahhhh"s and "oohhhh"s and "reaaaaaalllyy?" and "the 20's you said?"...

from the height of my ignorance: dev time and density

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