Surface developer vs. depth developer

[Ashfaque]

Hello,

I came across the following sentence in the technical datasheet of Rollei RPX 400:

Prewashing is permissible, but not necessary, with surface developers. With depth developers, prewashing is always recommended.

Can you please explain for a novice like me the pros and cons, and the differences between surface and depth developers?

Also, which category does Kodak HC-110 fall into?

Bests,
Ashfaque

 

[Gerald C Koch]

An example of a surface developer would be the Beutler developer. It is highly dilute and so exhausts near the surface of the emulsion. This increases acutance since there is little image spread. Most commercial developers like HC-110 do not fit in this category unless they are highly diluted. As to why Rollei would make such a statement I haven't a clue. I might add that I am not a fan of pre-soaking as is Ilford which does not recommend it for its film.

 

[Ashfaque]

Thanks Gerald.

 

[Mustafa Umut Sarac]

Thank you for question and answer , this was new to me.

 

[Gerald C Koch]

I might add that surface developers can use methods other than developing agent exhaustion. Among other techniques the amount of sulfite can be limited. An example of this would be Kodak's HDD High Definition Devevopler

 

[Keith Tapscott.]

Hello,

I came across the following sentence in the technical datasheet of Rollei RPX 400:

Can you please explain for a novice like me the pros and cons, and the differences between surface and depth developers?

Also, which category does Kodak HC-110 fall into?

Bests,
Ashfaque

AFAIK, a depth developer is a particular type of fine-grain developer. Rollei RLS (Rollei Low Speed) is described as a depth developer and this probably applies to Perceptol and Microdol-X as well. Why a pre-soak is recommended, i don't know.

Most modern B&W films films have more than one emulsion layer, hence the phrase 'depth developer'.

 

[Keith Tapscott.]

Rollei RLS deep layer depth developer.

https://www.fotoimpex.de/shopen/chemistry/rollei-rls-low-speed-developer-1000-ml-concentrate.html

 

[Ashfaque]

Thanks Keith. I guess Windisch's famed developer falls within 'surface' category as well.

Bests,
Ashfaque

 

[Gerald C Koch]

The only true "depth" developers that I know of are based on Amidol as the developing agent used in a carefully buffered environment. They are used to develop nuclear emulsions and are not used for general purpose photography. They take advantage of the fact that Amidol is the only developing agent that can work in an acid environment. As Amidol molecules migrate from the emulsion surface they experience an ever increasing pH which encourages development. The bottom of the emulsion has the greatest amount of development. I suppose if you are Roollei you can call your developer anything you want.

 

[Alan Johnson]

"When I use a word", Humpty Dumpty said in a rather scornful tone, "it means just what I choose it to mean - neither more nor less". (Alice's Adventures in Wonderland),
From the massive development chart, the developers referred to in Post 6 have a long development time compared with D-76 and Xtol, it may be that the developing agents diffuse to a greater depth in the emulsion in these cases.

 

[Gerald C Koch]

the developers referred to in Post 6 have a long development time compared with D-76 and Xtol, it may be that the developing agents diffuse to a greater depth in the emulsion in these cases.

Perhaps, but when the developing agent gets to the bottom of the emulsion does it find a beneficial environment: pH, bromide concentration, etc.

 

[Alan Johnson]

I did not find the term "Depth developer" in Mason, Mees & James, or Anchell and Troop, it appears to come from Germany, I'm just trying to figure out why they use it.

 

[Gerald C Koch]

Developers like Perceptol, Microdol-X, and D-25 are high solvent formulas. Their pH is adjusted to lower the rate of development to maximize the contact time between the silver halide and the solvent either sodium sulfite or sodium chloride. Raising their pH to a more normal value destroys their solvent action. While it is possible for both effects to be responsible for these developers it does seem rather unlikely. This is particularly true when the term is not found in the classic texts. It would be nice if Rollei defined what they meant by the term. As I pointed out true depth developers are a rather restricted category which are not intended for pictorial use.

 

[Rudeofus]

Many, many moons ago, photographic emulsions were much thicker than they are today, and one could reach typical density values by fully developing the outer most layers of such emulsions, and this would be called surface development. If one used a developer which only partially developed the bulk of the emulsion layer, the same density could be reached, and this would be called 'depth development'. Typically this would be achieved by using a slow developer in order to minimize diffusion time effects, and Gerald Koch indicated another trick to achieve this.

Since surface developers effectively emulated a thin emulsion, there is a good chance that they created sharper results. Depth developers, on the other side, developed more grains to a lesser extent, thereby likely giving much finer grain. Note, that this is, by far, not the only way to affect granularity and sharpness of photographic images. I am also not entirely sure, whether this differentiation still has the same relevance today, when most film stock is coated as thin emulsion.

 

[Gerald C Koch]

Many, many moons ago, photographic emulsions were much thicker than they are today, and one could reach typical density values by fully developing the outer most layers of such emulsions, and this would be called surface development. If one used a developer which only partially developed the bulk of the emulsion layer, the same density could be reached, and this would be called 'depth development'. Typically this would be achieved by using a slow developer in order to minimize diffusion time effects, and Gerald Koch indicated another trick to achieve this.

The Rollei developer uses ammonium chloride as a silver halide solvent. Its use for this purpose is many decades old but was abandoned years ago because of the danger of dichroic fog with modern emulsions. It would work as stated in the quote to develop more grains to lesser degree in the emulsion.

 

[Alan Johnson]

In this context , "Depth developer" appears to be a German term which has been translated into English, I doubt this Rollei developer has any magical properties not possessed by its equivalents Microdol-X and Perceptol which I have never seen referred to as depth developers.

 

[Rudeofus]

In this context , "Depth developer" appears to be a German term which has been translated into English, I doubt this Rollei developer has any magical properties not possessed by its equivalents Microdol-X and Perceptol which I have never seen referred to as depth developers.

Looking at German sources, there appear to exist two kinds of "Tiefenentwickler" aka "Depth developer":

1. "Schichttiefenentwickler", which seem to represent what I described in my previous posting. According to this link a common way to create such a developer is by using dev agents with long induction period.
2. "Korntiefenentwickler", which do not only develop latent image centers on the surface of a silver halide grain, but also if they are buried within. This is usually done by adding a solvent to the developer.

The Rollei developer uses ammonium chloride as a silver halide solvent. Its use for this purpose is many decades old but was abandoned years ago because of the danger of dichroic fog with modern emulsions. It would work as stated in the quote to develop more grains to lesser degree in the emulsion.

Rollei's RLS seems to be the second kind of depth developer, using a strong solvent to create a "Korntiefenentwickler". As already stated by Alan, it most definitely is not the only of its kind.

 

[Gerald C Koch]

I would also say that solvent type developers might be less effective. PE mentioned that modern emulsions can contain up to 9% iodide. Silver iodide is the hardest of the silver halides to dissolve. Witness the longer fixing times for some of today's films.

 

[Andrew O'Neill]

This is an interesting thread, as I wrap my head around the differences between surface and depth developers. Anyone else care to add more insight into this?

 

[DeletedAcct1]

An example of a surface developer would be the Beutler developer. It is highly dilute and so exhausts near the surface of the emulsion. This increases acutance since there is little image spread. Most commercial developers like HC-110 do not fit in this category unless they are highly diluted. As to why Rollei would make such a statement I haven't a clue. I might add that I am not a fan of pre-soaking as is Ilford which does not recommend it for its film.

Maybe because in theory gelatine swelling facilitate deeper developer access .

 

[Alan Johnson]

In post 1 here I made scans which may show that surface developers Neofin Blue and Rodinal tend to look sharper than Xtol which redeposits silver, maybe deeper into the emulsion and doesn't have quite the same contrast on this micro scale. Pyrocat which is also sometimes called a surface developer manages to look sharper but may this property at higher print size.

Scans retain developer properties

Here I scanned some chart lines (the full 35mm frame is about 50x the width of the chart) made from Ilford Delta 100 developed in acutance developers Rodinal 1:50 and Neofin Blue, solvent developer Xtol, and pyro developer Pyrocat HD.Scans were made with a Plustek 8100 set at 7200dpi which...

www.photrio.com

 

[pentaxuser]

Doesn't #16 sum it up?

pentaxuser

 

[runswithsizzers]

This is an interesting thread, as I wrap my head around the differences between surface and depth developers. Anyone else care to add more incite into this?

I think you mean "insight"? Although we do seem to get a certain amount of incite around here, too. ;-)

 

[Andrew O'Neill]

I'm just wondering how relevant the term "depth/surface" developer is today, with thin emulsion films. Quite honestly, I've never heard of this term until very recently. And what is the example of a "surface" developer? Are these types compensating developers? Any developer that is diluted? Semi-stand? Crawley's Acuspecial?

 

[Andrew O'Neill]

I think you mean "insight"? Although we do seem to get a certain amount of incite around here, too. ;-)

yes, thank you...Fixed.