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kjsphoto

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Ok,

The more I read abotu 2 bath developing the more I am getting confused.

Ok for example. I have a contrasty scene. O am using let say 100 spped film. I go N-1 (iso now 50) and I underdevelop. Take time and substract 20-30%. I think this is for straight developing now 2 bath. Now with tow bath you jsut develop 4 and 4 right?

What if the scene is flat do you puch a bit say N+1 (ISO 200) and add a bit of time to the developing? What abotu in a two bath developer? Still 4 and 4?

I am just trying to get a grasp of this as I never used two bath before.

Thanks,

Kev
 

glbeas

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Two bath usually can't be used with zone developing. Most folks report that two bath developers give a lower contrast image than single bath. This is because of the way a two bath works.
The first bath soaks the emulsion with one part of the developer, I think the activator part like Metol, then it is transferred to the second part with the alkali to make it work. This goes on to exhaustion using only the components in the emulsion. The result is highlights use up the developer before the shadows and therefore get less development.
Therefore leaving the film in the developer longer will not add any more density to the highlights but may bring up more shadow detail on some films.
It makes a good compensating developer.
 

Donald Miller

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kjsphoto said:
Ok,

The more I read abotu 2 bath developing the more I am getting confused.

Ok for example. I have a contrasty scene. O am using let say 100 spped film. I go N-1 (iso now 50) and I underdevelop.

Take time and substract 20-30%. I think this is for straight developing now 2 bath. Now with tow bath you jsut develop 4 and 4 right?

What if the scene is flat do you puch a bit say N+1 (ISO 200) and add a bit of time to the developing? What abotu in a two bath developer? Still 4 and 4?

I am just trying to get a grasp of this as I never used two bath before.

Thanks,

Kev

It appears to me that you are equating N minus and N plus with film speed adjustment. N minus and N plus are indicators of development adjustment rather then exposure adjustments. Contrast is determined by development.

Having said that one would normally make adjustments to film speed when development times depart from "normal". For instance in a N minus one (appr. SBR 8) I would decrease film speed from normal by 1/3 to 1/2 stop to support shadow detail (give more exposure). In a N plus one (appr. SBR 6) I would increase film speed by 1/3 to 1/2 stop to obtain greater effect on the negative density range (give less exposure).

As Gary stated split bath development is a compensating development and would normally be used in situations of excessive contrast. I personally would not use it unless and until I exceeded SBR 9 (appr. N minus two). There are many "tools" in photography. The matter is using the proper tool at the proper time. One would not normally attempt to fry eggs with a ball pein hammer.
 

skahde

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glbeas said:
The first bath soaks the emulsion with one part of the developer, I think the activator part like Metol, then it is transferred to the second part with the alkali to make it work.

This is what the books say but did you ever try to "soak" the film in bath A and fix it afterwards leaving out bath B? I did this unintentionally (doh!) with the Stöckler formula but, big surprise, the only thing missing was a bit of shaddow density.

Honestly It wasn't that much of a surprise as I previously read an arcticely about the Stöckler formula written by James Kates who took the time to really dig into this field and do some densitometry. To summarize his results: most of the development happens in bath A, bath B intensifies the shaddows. Curve slope of midtones and highlights can be adjusted by time in bath A. Zone system methods can be applied.

Here is the link, it is well worth reading:
http://www.largeformatphotography.info/twobath/

Obviously with the two-bath formulas still in use today like Barry Thorntons's Metol two bath, Divided D-23, Divided D-76 (you name it), the high amount of sulfite provides enough alkalinty for the development to take place. On the Pure silver list I asked for forrmulas where this might not be the case. The formulas that turned up where obscure at best.

Stefan (still repeating myself...)
 

Tom Hoskinson

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Actually, the developing reagent (in the case of split D-23 and/or Stoeckler) is Metol. Since Metol requires sulfite as a preservative and sulfite is a weak alkali (and thus an activator), the "A "solution will develop film all by itself. The Stoeckler "B" bath is just Borax and water.

In principal, you can split nearly any developer into the developing reagent (in some form of preservative solution) and the alkali.

Here is the recipe for a Diafine-like split Phenidone-Hydroquinone (PQ) developer:

"A" Bath

Boiled Water @125 degrees 750ml
Sod. Sulfite 35.0 grams
Hydroquinone 6.0 grams
Phenidone 0.2 grams
Sod. Bisulfite 6.0 grams
Boiled Water to make 1.0 liter


"B" Bath

Boiled Water @125 degrees 750ml
Sod. Sulfite 65.0 grams
Sodium Metaborate 20.0 grams
Boiled Water to make 1.0 liter


Can be used between 68-80 degrees
Do not pre-soak.
Soak in bath A for 3 minutes.
Move to bath B for 3 minute soak
Do not rinse in between baths.
Do not use acid stop bath; use water rinse.
A non-hardening fixer is recommended.

Both the "A" bath and the "B" bath can be reused.

You can change the dilution of the "A" bath for one-shot use to develop films like Kodak Tech Pan.

You can also change the alkali in the "B" bath to increase and decrease the contrast and apparent grain. For example, you can replace the metaborate with carbonate or with borax.
 
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My experience with two baths devs is almost only with the above Diafine lke formula.
From all I've read, it is mandatory that sol A is neutral to acidic to get the 'two baths' effects.
My conclusions from the above:

- There is no significant speed gain (with TX, almost zero).
- Its very compensating, so it is good at taming highlights as in night strret photos or flash.

I use it with TX @1250.

I will be posting a couple of night photos in the technical gallery.

Jorge O
 

Ole

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My "Bridge" photo was developed in divided D-23 (or D-23 with borax afterbath) to tame the contrast, which was about 14 zones... It worked.
 
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