Question about N-1 development

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Alastair Moore
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Question about N-1 development

Postby Alastair Moore » 15 Feb 2013, 19:08

So you've metered as figured out you're going to need N-1 (or 2, 3) development to bring your highlights in. I understand the decreased development will lower the highlights from say zone X to zone VIII, why does it not lower the shadows from zone 3 to 2 or 1? Basically why isn't the tonal range shifted entirely?

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RoganJosh
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Re: Question about N-1 development

Postby RoganJosh » 16 Feb 2013, 01:45

I couldn't tell you the chemical reason as to why this happens off the top of my head but you should know that the low values are still slightly decreased with underdevelopment - just not as much as the high values. Read AA's the Negative, it literally has an entire chapter on this stuff.

Walter Glover
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Re: Question about N-1 development

Postby Walter Glover » 16 Feb 2013, 02:15

Density increases and decreases in a LOGARITHMIC scale rather than an ARITHMETIC scale. It is why increases or decreases in density of one or two stops in the area of the high values call for adjustments of only a fraction of a stop at the low values.
Walter Glover

"Photography was not a bastard left by science on the doorstep of art, but a legitimate child of the Western pictorial tradition." —Robert Galassi

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Maris
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Re: Question about N-1 development

Postby Maris » 16 Feb 2013, 09:31

The chemical basis for N minus development becomes obvious if you have ever had the uncommon experience of watching sheet film develop. I don't have an infrared viewer so I've never seen panchromatic film in the developer but orthochromatic and blue sensitive films work in the same way and can be observed under deep red safelight.

The least exposed parts of the film corresponding to Zones I to III (say) develop to completion in the first few seconds. Virtually all the exposed silver halide gets reduced to silver and the process effectively stops in the "thin" parts of the negative. Also as development continues more and more of the unexposed silver halide gets slowly reduced to silver too and this forms base fog.

The mid tones and highlights above Zone IV have reserves of exposed silver halide that developer continues to find as it diffuses through the emulsion. Extending development increases the amount of silver formed and the optical density goes up. By stopping development at a certain point one can limit a particular density to a given exposure Zone provided that exposure zone has not already been developed to completion.

It is possible to extend development so that ALL exposed silver halides are reduced to silver. This has been called development to gamma infinity. The main proponent of this technique was Ansel Adams' sworn enemy in all things photographic: William Mortensen. I suspect that Mortensen delighted in gamma infinity because it is the exact opposite of the Zone System.

A modern idea is that the availability of variable contrast photographic paper obviates the need for N+/-1 and N+/-2 development regimes. Going up or down 1 or 2 steps in paper grade delivers remarkably similar zone expansions and contractions when combined with standard N development.

Another point is that a modern film like Tmax 400 has a linear range of at least 14 zones. The highlights don't block even with what seems to be gross overexposure. I confess that I have occasionally forgotten to stop a view camera lens down and given an 8x10 sheet 7 stops overexposure. The super black negative when contacted out still delivers all the tones in an orderly fashion. Admittedly you would not want to put such a negative into an enlarger or (perish the thought) into a scanner.

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Re: Question about N-1 development

Postby Walter Glover » 16 Feb 2013, 09:40

Maris wrote:The main proponent of this technique was Ansel Adams' sworn enemy in all things photographic: William Mortensen. I suspect that Mortensen delighted in gamma infinity because it is the exact opposite of the Zone System.


I love the baby Mortensen because he inspired St. AA to expose just exactly what a heinous arse he really was. "The Anti Christ Of Photography" — give me a break! Especially when expressed by a self-confessed non-believer.

Gives new meaning to bAAh-humbug.
Walter Glover

"Photography was not a bastard left by science on the doorstep of art, but a legitimate child of the Western pictorial tradition." —Robert Galassi

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Alastair Moore
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Re: Question about N-1 development

Postby Alastair Moore » 17 Feb 2013, 09:01

Cheers all!

L2obin
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Re: Question about N-1 development

Postby L2obin » 18 Mar 2013, 08:21

Shadows take the least amount if time to develop, hence they are done developing before you reduce the time to cut the highlights.


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