Loss of Film Speed ??

[sdifaz]

Hi All,

 

I have been trying out different developers lately, after years of using

Ilfosol S & Delta 100 I thought I'd try something new. I have read various

developer specs from Ilford & Kodak. On the Ilford website under the Perceptol

spec they make the following statement :

 

" Designed for use when very fine grain negatives are required but a decrease

in film speed is not important "

 

I understand the fine grain bit no problem! But, my question is this: What

causes this decrease in film speed? When does it take place? Should I rate my

Delta 100 at 50ASA when I know I am going to use Perceptol? I've seen this

statement when looking at other manufacturers specs too & I'm trying to

understand what the meaning is & how it should affect my exposure &

development? Perhaps I'm missing something obvious but if anyone can clarify

then I would appreciate the info! Regards Simon

[marc_leest1]

It's all about densities .... some chemicals = developers, need more exposure (read lower iso ) to obtain the same density levels than other developers. That's it

[marc_leest1]

I could add that certain types of light eg. halogen flood light against flash light will reduces actual sensitivity due to spectral properties.

[john_shriver]

Different chemicals react differently with the exposed silver iodide grains. If you want to learn in-depth, get a copy Anchell and Troop, "The Film Developing Cookbook". Buy new or used, or borrow through your local public library.

 

Perceptol and Microdol-X (and to some degree Ilfosol S) trade off film speed and resolution (acutance) for less grain. They basically make the grain into softer mush. In some cases, it may be the look you want.

[frank.schifano]

Microdol-X is also one of those super fine grain developers when used at full strength. At full strength, or so the story goes, the developer has enough sodium sulfite to to act as a silver solvent. There is also a bit of sodium chloride in the developer as well, but I'm unsure how that works. The developer may also encourage the dissolved silver to re-plate back onto the film more or less uniformly, raising the base fog level. Now realize that film speed can be thought of as the amount of light needed to produce a density on the film just a bit more than the density of the film base + normal fog. Shadow densities are pretty thin to begin with, and some of the very little bit of silver making up these thin areas is eroded away by the sodium sulfite and sodium chloride in the developer. Added to that, you have a possible increase in base fog further lowering the delta between the base fog density and the first perceptible shadow density. So how to compensate for that? Allow more exposure. About 1 stop for Microdol-X and Perceptol is what you need to bring your shadow densities back up to where they need to be.

 

I am curious to know why you want to use a fine grain developer on a film like Delta 100? It is already a very fine grained film. I doubt that you'll see much of an improvement. You might even find that the resulting photos may loose a bit of sharpness because whatever grain there is has been softened up by the developer. These developers make sense if you have a fast film, cannot switch to a slower film, can give up a stop of speed, and want finer grain.

[frank.schifano]

...or as John wrote, you're aiming for that soft look.

[jim_appleyard]

According to A&T, sodium chloride (salt if you're a "chemist" like me) produces a fine-grain image w/o loss of film speed.

[chris_waller]

It's because ultra-fine grain developers contain higher levels of solvents which dissolve the edges of the halide grains. In the process they dissolve away some of the latent image sites thus reducing effective film speed. The data supplied with Perceptol (or to be found on Ilford's website) will give you the appropriate ASA speeds and development times.

[sdifaz]

As always thanks for the input guys, from the explainations given I now get the idea, or the chemistry... I am interested in Franks point though about using Microdol-X and/or Perceptol with Delta 100. I am looking for fine grain & sharpness from this film so can anyone recommend a tried & tested developer that would be suitable?!

 

Regards, Simon

[jim_appleyard]

Nothing is more tried and true than D-76. With Delta 100, the 1+1 dilution should be a good compromise between sharpness and fine grain. You can also dilute it 1+3 if you want things a bit sharper.

 

You can also dilute Microdol-X 1+3. I don't know if this will be any sharper/fine-grained than D-76 1+1, but it might be worth a look.

 

There are many other standard devs from other companies and the rest of the gang will chime in with their favorites.

 

Pick up copies of Anchell's "Darkdoom Cookbook" and Anchell & Troop's "Film Developing Cookbook". Lots of info re: sharpness v grain.

[frank.schifano]

FWIW, I like XTOL with these "newer technology" emulsions a little bit better than D-76. Both are very good, but XTOL give me just a little bit more of an edge in sharpness and fine grain. It's not much, and nothing you'd probably notice with modest enlargements up to about 8x. After that, you'd need to compare prints where the only different variable is the film developer to see the difference.

[maciej_jezewski]

Hi All,

 

Simon, I?ve been puzzled by this question for some time now, so glad to join on the topic, but this time with further questions to all contributors...

Thing is, I dont get it,

Frank, thanks for valuable info, but is the loss of film speed with super fine grain developers only noticed in the shadow details?

if film speed is density resulting from exposure, wont there be loss of density throughout - shadows, midtones and highlight??

And then what happens if you take a speed increasing developer - will increased speed mean higher density just in shadows or throughout?

 

but the real question (to me) is WHY?

As I understand it - and I am really just a beginner in film developing, just doing my tests with all films and some developers - grain size defines film speed, it is predetermined by the producer, during the development the silver halide crystals containing the latent image are reduced, read dissolved, we?re left with silver that may or may not clump together to form graininess.

 

so if film speed was defined by the halide grain size - the bigger, the quicker response to photons because of the volume? - then, after developing there is NO GRAIN, no crystals, just silver threads, or fluffy bits or whatnot that we may perceive as graininess.

 

So, if it is said that super fine grain developers produce fine "grain", why is there film speed loss, read less silver,less density???

 

Chris - you say "fine grain developers contain higher levels of solvents which dissolve the edges of the halide grains. In the process they DISSOLVE AWAY SOME OF THE LATENT IMAGE SITES thus reducing effective film speed....

Is that it??? where do you have this info from?

and what, then, happens with speed increasing developers???

do they produce more silver, more density - and why that??

 

I am lost and still waiting for my ordered copy of Anchell, so I would be really happy about any clarification on this - many thanks in advance!

Maciej

[frank.schifano]

"Thing is, I dont get it, Frank, thanks for valuable info, but is the loss of film speed with super fine grain developers only noticed in the shadow details?"

 

No, silver is dissolved from the entire image. The shadow areas, which have very little silver to begin with are dissolved away to the point that there is not enough left to form any useful amount of density.

 

"...silver halide crystals containing the latent image are reduced, read dissolved, we're left with silver that may or may not clump together to form graininess."

 

Not exactly. Reduced, in this case, means chemically changed from a sliver salt, the halide, to metallic silver.

 

"...fine grain developers contain higher levels of solvents which dissolve the edges of the halide grains. In the process they DISSOLVE AWAY SOME OF THE LATENT IMAGE SITES thus reducing effective film speed.... Is that it??? where do you have this info from? and what, then, happens with speed increasing developers??? do they produce more silver, more density - and why that??"

 

Every silver halide grain is affected by exposure to light, some more than others dependent upon the amount of light received. There is a threshold below which the developer cannot trigger the reaction to convert the halide to metal. Speed increasing developers lower that threshold.

 

Read A&T, it will become more clear.

[patrick_gainer]

The characteristic curves for different times of development have different contrast indices. The average slopes throught the usable parts of each curve generally meet at some point. When that point is below the horizontal axis, the curves are said to be depressed. Bromide, either added or generated by development, tends to depress the curves. I would look to bromide as the cause of apparent loss of film speed rather than dissolving of grains. Many fine grain developers have some bromide content. You can test this idea for yourself by adding bromide to full-strength D-76. Do a test strip without bromide and another with it.