Scientific reason why some developers causes decrease film speed

[Fatih]

Hi all,
I have had the source which explains this scientifically but for some reason, I cannot find it anymore.
What is the scientific or chemical reason why some developers causes effective film speed reduction, effective film speed increase or full film speed. For some reason, the shadows don’t develop fully, and why would that happen?

Is it just because short development times causes speed reduction and long development times causes speed increase as shadows don’t have enough time to fully develop and the opposite for the latter one?

I can also understand some ultra fine grain developers causes effective film speed loss, ie loss of details as they eat away little remaining silvers in the shadow areas but like Rodinal which is said to cause film speed reduction but a course grain developer, why does it cause effective film speed loss.

Cheers,
Fatih

[Robert Bowring]

Developers do not increase or decrease film speeds.

[Peter De Smidt]

Sure they do. When developed to the same contrast, Microdol-X and Xtol, for example, give different film speeds, i.e. Zone 1 at least .1 above film base plus fog.

[paulbarden]

Developers do not increase or decrease film speeds.

Look up FX-37. It was formulated specifically to achieve an increase in film speed, and it does so, by at least 1/2 stop with most films.

[Bruce Watson]

What is the scientific or chemical reason why some developers causes effective film speed reduction, effective film speed increase or full film speed. For some reason, the shadows don’t develop fully, and why would that happen?

It would take a book to explain it. Fortunately, that book has been written. It's called The Film Developing Cookbook (https://www.amazon.com/Film-Developing-Cookbook-Bill-Troop/dp/1138204870) by Anchell and Troop.

[Bernice Loui]

The entire process of B&W image making cannot be separated. Yes, developers (reduction process) do bend effective film speed. But it interacts with the print making process. Negatives used for traditional B&W prints (silver gelatin) might not do well for alternative printing process like carbon printing.

Essentially, film _ film processing _ print making are all interactive and should NEVER be separated from the goal of the print image.

Recommended to read pages 21 to 40 in this book
http://www.processreversal.org/public/text/Jacobson_developing.pdf

which explains the development process, how film reacts to the development process and how each component of the developer alters the development process (in the next chapter in this book).

There have been renewed interest in developer agents like Pyrogallic acid and others like XTOL and ... they ALL remain part of the print making process which MUST work together as a complete system from film exposure in camera to the finished print.

Key is figuring out what photographic materials work for your print making goals, learn and know them well, then apply what has been learned and practiced to fit your expressive print making needs. Experiment and tinker yes, but at some point this needs to stop once sufficient mastery of these materials and process has been achieved which brings forth the goal and objectives of expressive image making.


Bernice

[SergeyT]

Developers do not increase or decrease film speeds.
+1
It is a property of the emulsion

[reddesert]

Let's set aside the question of whether film speed (as in ISO) can actually be changed, and talk about shadow detail instead. Ask the question of why some developers might result in more or less shadow detail with normal development.

It's not just longer developing times - generally you can develop longer than a recommended time but you'll mostly increase contrast without improving the shadows much.

The action of film development is to convert exposed, latent silver halide crystals into metallic silver. During this process, adjacent halides become clumped and developed together. That is, the individual halide crystals are much smaller than what we see as "grains" in the developed film. I believe that a large part of the activity of developers is how they extend development from one latent crystal through its neighbors.

Some developers have a more aggressive solvent effect on the crystals, here I quote from "The Darkroom Cookbook" by Steve Anchell: "All films have a grain structure predetermined by the manufacturing process. ... Fine-grain developers tend to inhibit acutance (sharpness). This is because they effectively etch each grain particle into individual 'islands.' These islands do not connect with one another, as do less fine grains that are clumped together. The result is that visible lines in the image that should appear continuous are broken into small segments as they jump from grain to grain."

Here he's talking about the effect on acutance, not speed/shadow detail, but you can begin to see how the solvent action on particles will trade off between acutance, shadow detail, and the appearance of graininess. A developer like Rodinal preserves acutance by enhancing edge effects, I believe.

[Drew Wiley]

Changing the characteristic curve of any particular film often DOES in effect change its real-world film speed. Launching off the toe quicker, for example, means that you need less exposure to get the same shadow gradation or printable threshold density, and therefore obtain a faster film speed. "Expose for the shadows, develop for the highlights." The devil is in the details, and that's why there are all kinds of books and websites dedicated to that. There's no simple generic equation. Lots of variables involved. So it's NOT JUST a property of the emulsion. How a cake tastes is not due just to what ingredients come the cake mix box and gets poured in a pan, but about how you specifically bake and frost it too.

Anyone who has densitometer plotted a substantial "family of curves" for a particular film knows how the effective threshold take-off of that film can in numerous instances be affected by not only the degree of development, but by the type of developer too. Likewise, controlling things at the top end via staining developers, for example, inherently alters what is needed further down or not.

[Michael R]

Fatih,

Unfortunately there is no single answer. The type of film emulsion is a very important variable, of course. When it comes to how a developer behaves with a specific film, there are a variety of mechanisms at work which can effect the shape of the film’s characteristic curve and therefore potentially effect “emulsion speed” (choose a definition first) to some degree.

However when it comes to properly formulated general purpose developers, differences in emulsion speed are small. In many cases they are negligible. The things you typically read about differences in speed like half a stop (or more) are almost always highly exaggerated, especially when speed is said to be increased. There are a few special cases where you lose maybe up to half a stop, but beyond that it is largely a non-issue.

[Bernice Loui]

Gonna be more than +/- " half a stop"...

Read this book:
http://www.processreversal.org/public/text/Jacobson_developing.pdf


Another VERY common reference from back in the day,
~Photo Lab Index Lifetime Edition.~
https://www.abebooks.com/servlet/BookDetailsPL?bi=22404054058&cm_mmc=ggl-_-COM_Shopp_Rare-_-product_id=bi%3A%2022404054058-_-keyword=&gclid=Cj0KCQjwlMaGBhD3ARIsAPvWd6iKNjB2rUa6yIYOanHcHJ_68Hy6sQ4b2yDMzadGfsf7eUMThaondX4aAsg2EALw_wcB




Bernice




However when it comes to properly formulated general purpose developers, differences in emulsion speed are small. In many cases they are negligible. The things you typically read about differences in speed like half a stop (or more) are almost always highly exaggerated, especially when speed is said to be increased. There are a few special cases where you lose maybe up to half a stop, but beyond that it is largely a non-issue.

[Michael R]

I’m familiar with them.

My statement stands.


Gonna be more than +/- " half a stop"...

Read this book:
http://www.processreversal.org/public/text/Jacobson_developing.pdf


Another VERY common reference from back in the day,
~Photo Lab Index Lifetime Edition.~
https://www.abebooks.com/servlet/BookDetailsPL?bi=22404054058&cm_mmc=ggl-_-COM_Shopp_Rare-_-product_id=bi%3A%2022404054058-_-keyword=&gclid=Cj0KCQjwlMaGBhD3ARIsAPvWd6iKNjB2rUa6yIYOanHcHJ_68Hy6sQ4b2yDMzadGfsf7eUMThaondX4aAsg2EALw_wcB




Bernice

[Bernice Loui]

Don't argue to the sake of arguing..

From AA's book, The Negative.
216914


From Gordon Hutchings, The Book of Pyro.
216915

Why is importance of film testing with a given developer SO important for the print making process? These are only a few written words of reference, LOTs more has been written on this topic by MANY individuals.

B&W film and it's print making process is NOT the same as color film, why?


Bernice







I’m familiar with them.

My statement stands.

[LabRat]

One developer I made from scratch really did give me a one stop true increase in film speed, but rare among developers...

The old photographer's rule still applies; "expose for the shadows, develop for the highlights"... You expose enough for detail in the shadows to appear, but highlights are islands that produce much physical/chemical activity that will block up if allowed to overdevelop... (Shadows develop early in development and remain mostly unchanged throughout development until fog starts to build-up...) So you need enough exposure for the shadows to start, but not develop too much for film to go into D-max where there will no separation in upper highlights... That is your mission...

Read up on all theory you can, but after several chapters of theory, it's time to get your hands wet with testing... Decide on one film/one developer, and follow the instructions to calibrate that combination and stick with it... Pretend it is the last film and developer available on this world and use all the time... You can later try other combinations on the side out of curiosity, but standardize one combination first...

You will be getting better results you didn't expect from the get-go...

Steve K

[Bernice Loui]

For B&W films and print making,

This, "Decide on one film/one developer, and follow the instructions to calibrate that combination and stick with it... Pretend it is the last film and developer available on this world and use all the time... "

Cannot be repeated or ingrained enough as the basics to GOOD B&W print making. Without a single know and well-proven point of reference, the print making process becomes difficult to control and produce expected or desirable print results.

Part two of this becomes print making which is interactive with the negative, they work together as a system and needs to be set up to be predictable as reasonable.


Bernice




Read up on all theory you can, but after several chapters of theory, it's time to get your hands wet with testing... Decide on one film/one developer, and follow the instructions to calibrate that combination and stick with it... Pretend it is the last film and developer available on this world and use all the time... You can later try other combinations on the side out of curiosity, but standardize one combination first...

You will be getting better results you didn't expect from the get-go...

Steve K

[LabRat]

Hey, good negs are easy to print!!! ;-)

Focus on neg making as a primary photo objective...

Steve K

[Michael R]

Ansel Adams was a great photographer, but if you want to talk seriously about things such as emulsion speed, sensitometry or photochemistry, you don’t go to Adams, Hutchings, etc. In any case, Adams did not say developers make big differences in emulsion speed.

Yes, a lot has been written by many people, and a lot of it is wrong. There are good sources, and a whole lot of bad sources.

Why is film testing with a given developer so important for the print making process? It really isn’t that important. The control is in the printing. Of course you test to find a suitable development time, and you have to learn to use an exposure meter, but all the stuff about testing for film speeds is basically irrelevant and/or incorrect, as long as one is using a properly formulated general purpose developer with a properly designed/manufactured general purpose film.


Don't argue to the sake of arguing..

From AA's book, The Negative.
216914


From Gordon Hutchings, The Book of Pyro.
216915

Why is importance of film testing with a given developer SO important for the print making process? These are only a few written words of reference, LOTs more has been written on this topic by MANY individuals.

B&W film and it's print making process is NOT the same as color film, why?


Bernice

[Jos S]

Sulphite acting as solvent, as in Perceptol and Microdol-X leads to finer grain but also to a loss of density?

[Paul Ron]

For B&W films and print making,

This, "Decide on one film/one developer, and follow the instructions to calibrate that combination and stick with it... Pretend it is the last film and developer available on this world and use all the time... "

Cannot be repeated or ingrained enough as the basics to GOOD B&W print making. Without a single know and well-proven point of reference, the print making process becomes difficult to control and produce expected or desirable print results.

Part two of this becomes print making which is interactive with the negative, they work together as a system and needs to be set up to be predictable as reasonable.


Bernice

exactly on point!

seems the argument is over a measely half stop... does it make that much difference? no!

best advice is standardise what ever you are using to give you the most consistant results in the print... that takes alot of experimenting starting from exposure to enlarger.

now lets hear more about those chemicals in the soup that acts on the image?

[Fatih]

Sulphite acting as solvent, as in Perceptol and Microdol-X leads to finer grain but also to a loss of density?

This is what I was looking for. Hence diluted XTOL create larger grains but better emulsion speed as well compare to non diluted XTOL. Thank you.

[Bernice Loui]

Simplified summary, Silver Bromide in the film reacts with light reaching these SB crystals. Conversion of these SB crystals altered by light becomes metallic silver during the reduction process known as "Developing". Size of these silver bromide particles in the film relates to the film's sensitivity to light NOT "speed of the film".

Developers commonly consist of a developing agent (Elon-Metol, Phenidone, Pyrogallic, Amidol, hydroquinon, Glycin, Pyrocatechin and...) this is the chemical that acts to reduce the SB particles that has been affected by light into darkened metallic silver. To speed up this process an alkali like sodium carbonate or potassium metaborate or borax is added to increase ph. A Restrainer like potassium bromide to moderate the alkali accelerated development agent to reduce film fogging and a preservative like Sodium Sulfide. Large amounts of Sodium Sulfide results in solvency which has an effect of "washing away" some of the film grains resulting in what is perceived as "finer grain" grain developed film trading off acutance or edge effects.

Mild acidic stop bath rapidly halts the SB reduction process.

Fixer is a solvent that removes the non light reacted SB particles and other stuff like the anti-halation layer.
216930


To deny developers and development time does NOT have an effect on effective film speed is ignorant of what information is contained in the Gamma curve and how this related to print making. This is where a good densitometer can be extremely useful. Or, at the very least a good 18% gray card and stepped gray strip.

~Note there IS a difference between innate light sensitivity of a B&W film -vs- effective film speed. These two terms are NOT interchangeable and have distinct meaning.

The effective speed of a B&W film depends LOTs on the contrast range of the scene to be imaged, development process and print making process. It all works together as a system with the finished print as it's goal. This is why testing to determine effective film speed for a given film and amount of exposure driven by how the negative would be made into the finished print is SO important and why the "box" speed of the B&W film is not often relevant to gain proper control over the print making process.

Fact remains, a GOOD B&W film negative is much easier to print and allows artistic alterations during the print making process. Inferior negatives forces a struggle to make a some-what ok print.

While this applies to the traditional wet dark room print making process, due to the wide spread of scanning of negatives into digital files then "worked over" in software, it appears these time proven methods to produce good print making film negatives have become ignored in favor of "fix it in software"..


:)
Bernice

[Fatih]

Thank you very much all, and apologies for incorrect use of film speed. But thankfully some of you have understood me :)
I understand speed is measured for little density change in shadow areas and some developers give better results on those areas.

Purpose of my question is because I’m asked to write a post for reader in Turkey about technical bits of film, chemistry and everything about it. Due to currency economic situation, they don’t have a chance to try all the different developers and I got the task at least to show them different developers as well. Otherwise I’m all the way HP5, F100, Rodinal and XTOL guy and tried DDX in the past so I have a good selection of comparative negatives.

[Bernice Loui]

One more on the topic of "film speed"..

~Testing Black and White Film~
https://www.kennethleegallery.com/html/tech/testing.php#:~:text=If%20you%20like%2C%20test%20your,that's%20your%20usual%20shutter%20speed.


"Executive Summary: Almost everyone who does rigorous film testing ends up shooting at roughly one f/stop slower than box speed for normal development: 200 for HP5+ and TMY, 50 for FP4+ and TMX, etc. The more important issue is determining the development times which work for you. Even then, if your results are substantially different from others, you're probably doing something wrong."

Why?
Bernice

[Doremus Scudder]

Faith,

Maybe Stephen Benskin will chime in here: He and Michael R seem to be the real experts in this field, along with a few others. If he doesn't you may find answers by searching his older posts here and over on Photrio. Or you could PM him.

It seems to me that a lot of the discussion here confuses emulsion speed with personal E.I. (exposure index) that many photographers determine for themselves and which is based on a lot of rather non-scientific considerations including equipment variables, personal preference for shadow detail and separation, safety factors, metering techniques (e.g., consistent errors in metering or one's tendency to not place shadow values in the Zone one really wants, etc.).

ISO emulsion speed, while directly related to the "first excellent print" test, is defined by contrast gradient and curve shape, and a host of other emulsion-density-specific parameters including specific developer(s).

Some other developers do seem to affect the effective emulsion speed somewhat, as does developing to a higher or lower contrast than ISO standard. The former seems to be what you are interested in. There's a lot of discussion on this thread about topics tangential to this, which seem to me to not be what you asked about...

Best,

Doremus

[Bernice Loui]

Seems the root of this mis-understanding is much about the designed sensitivity of a given film to light (mostly fixed)-vs- effective film speed (mostly variable) which are two completely different items and are NOT interchangeable.


Bernice

[Fatih]

Also a similar question could be asked, why developer A is better than developer B for push processing.

So the info I could collect is;
Fine, extra fine grain developers causes a bit of speed loss due to solvent
High accutance developers causes a bit of increase
Rodinal, due to high dilation, works as compensating developer can cause a bit of loss

[Peter De Smidt]

Phenidone developers tend to give about a 1/3 stop boost over D76.

[Fatih]

Phenidone developers tend to give about a 1/3 stop boost over D76.

That’s great to know, XTOL and Microphen has it. I wonder why Rodinal manual says it has high emulsion speed yield when we know high dilation causes speed loss.

[Michael R]

Nice try. The root of the misunderstanding is bad information repeated over and over and over.


Seems the root of this mis-understanding is much about the designed sensitivity of a given film to light (mostly fixed)-vs- effective film speed (mostly variable) which are two completely different items and are NOT interchangeable.


Bernice

[Bill Rolph]

For those interested in some further reading, here is a good paper on the subject: Film processing for maximum sensitivity at moderate contrast (https://www.spiedigitallibrary.org/conference-proceedings-of-spie/0354/0000/Film-Processing-For-Maximum-Sensitivity-At-Moderate-Contrast/10.1117/12.933997.short?SSO=1). It is written by Lockheed for aerial photography purposes, and explores increases in both actual and effective film speed based on the developer. It is available free on Sci-Hub by pasting in the DOI, 10.1117/12.933997.

A line near the beginning:

"The developer and process reported in this paper could generate negatives within the ANSI contrast rules that still gave light meter measured best exposures 2 and 3 times the calculated ASA speed."

Likely not useful except very infrequently, but it is interesting reading.

[Paul Ron]

bill, thanks for the article. to download it you have to go to this link...
https://sci-hub.hkvisa.net/10.1117/12.933997#

[esearing]

One more on the topic of "film speed".


"Executive Summary: Almost everyone who does rigorous film testing ends up shooting at roughly one f/stop slower than box speed for normal development: 200 for HP5+ and TMY, 50 for FP4+ and TMX, etc. The more important issue is determining the development times which work for you. Even then, if your results are substantially different from others, you're probably doing something wrong."

Why?
Bernice

Because teachers have told the newbies to do so , then they continue to use the practice years after learning it. Corran and I once had a conversation about the treatment of FP4+ . He meters it at EI 64 or 80 but I set my meter to 100 for convenience. he puts his shadows at Zone 2 whereas I often put my shadows at zone 3 so our net exposure is somewhat the same or within 1/2 a stop. He uses Pyrocat HD at full strength for multiple sheets, but I use pyrocat-M diluted and longer processing times one sheet at a time. So placement of your tones has an effect , how you develop for time/contrast has an effect, then ultimately scan/paper choices have an effect. We all are taught to standardize these things but knowing when to deviate from the norm and experimenting is what makes photography as a craft more interesting. I think the accidents, failures, and mis-steps are also good teachers of what will and won't work in our practice. There is also a difference in need for consistency between commercial work for clients versus work for personal pleasure/artistry.

[LabRat]

Because teachers have told the newbies to do so , then they continue to use the practice years after learning it. Corran and I once had a conversation about the treatment of FP4+ . He meters it at EI 64 or 80 but I set my meter to 100 for convenience. he puts his shadows at Zone 2 whereas I often put my shadows at zone 3 so our net exposure is somewhat the same or within 1/2 a stop. He uses Pyrocat HD at full strength for multiple sheets, but I use pyrocat-M diluted and longer processing times one sheet at a time. So placement of your tones has an effect , how you develop for time/contrast has an effect, then ultimately scan/paper choices have an effect. We all are taught to standardize these things but knowing when to deviate from the norm and experimenting is what makes photography as a craft more interesting. I think the accidents, failures, and mis-steps are also good teachers of what will and won't work in our practice. There is also a difference in need for consistency between commercial work for clients versus work for personal pleasure/artistry.

You need a center baseline for your exposures... Its like levels... You know where your shadows will fall, and the highlight you can hold... You will know where it will land on your paper (with your process)...

Then creative control comes in to raise/lower the key of your scene, but can measure the extremes of the scene and decide how much/little is enough for those areas...

If you are calibrated, you know what you can get away with (or not)...

Steve K