I've quoted sources in the past Ron, I'm not going to post the same information again.
The facts are that excessive temperature shocks cause micro reticulation with a small number of films and Ron (PE) himself prefers to call the excessive grain "grain clumping" in previous threads. Again as he knows other APUG members have attested to having excessive grain when they've used Tmax & Neopan 400 when they were lax with temperature controls.
My OP comes from the early days of astonomical photography in which astronomers were concerned about three things:
1. Image movement (placing stars at the wrong location)
2. Image movement (placing spectral lines at the wrong wavelength)
3. Formation of clumps by image movement which would give the appearance of a false star.
This article disproved all of the items in up to 16 developers, at two temperatures and with and without hardener in the process. With careful examination, they ruled out any significant movement of the developed silver image.
I know that there are some strong opinions, but this evidence is rather compelling to me.
As pH and / or temperature go up, the developed silver image will change morphology and the image structure will look different to the human eye, but there has been no movement or merger ever shown.
PE
This article doesn't relate to reticulation caused by excessive temperature changes. At the time it was written all emulsions reticulated easily but I'd guess all photographers had seen reticulation first hand and books then stressed good temperature controls.
...from one of the works by Ross, to be cited below. Basically, he contends that some people claim to have seen clumps when viewing a film but what they are really seeing are the inevitable statistical patterns we see when we look at thousands upon thousands of grains stacked vertically. When we look at a cross section, they are separated into distinct grains.
This is what I always thought of as grain clumping. It's that film is a 3D medium -- the emulsion has depth. When you look through it, you look through all of it. In a heavily exposed area you might see thousands of grains, all stacked one above the other. But they aren't all the same size, or same shape. So they "overlap" and form a non-transparent grouping of grains that's bigger than any of the individual grains. Thus -- a "grain clump".
Density is formed by metallic silver grains, yes? More density means more grains. And more grains means more overlapping, which in turn means "grain clumps" which are "bigger". This accounts for the grainy highlights from most B&W negative films. Said another way, this accounts for the spread in the sizes of the visible grains -- resulting in a range of sizes -- which is why grain size is sometimes referenced as an RMS average size (whatever meaning this might have).
This was my interpretation, though I can't remember ever having seen it written down anywhere. How wrong am I?
This is what I always thought of as grain clumping. It's that film is a 3D medium -- the emulsion has depth. When you look through it, you look through all of it. In a heavily exposed area you might see thousands of grains, all stacked one above the other. But they aren't all the same size, or same shape. So they "overlap" and form a non-transparent grouping of grains that's bigger than any of the individual grains. Thus -- a "grain clump".
Density is formed by metallic silver grains, yes? More density means more grains. And more grains means more overlapping, which in turn means "grain clumps" which are "bigger". This accounts for the grainy highlights from most B&W negative films. Said another way, this accounts for the spread in the sizes of the visible grains -- resulting in a range of sizes -- which is why grain size is sometimes referenced as an RMS average size (whatever meaning this might have).
This was my interpretation, though I can't remember ever having seen it written down anywhere. How wrong am I?
Bruce;
You have it correct! In fact, you lead into the next phase of this.
RMS = Root Mean Square and is usually said RMSG where G = Granularity.
Grain varies with type of development (high solvent, low solvent) and other factors such as pH as I mentioned above. Haist shows micrographs of several types of grain. I have yet to see an authoritative post on grain clumping or micro reticulation.
So, here is a plot of Grain vs Density. Note how grain varies with development time! This is how our eye fools us into thinking something has happened and the explanation is not correct. Grain even varies with development time at equivalent density.
It was mandatory to study the image structure on every coating I made. This included photo micrographs and electron micrographs, RMSG, etc.. I coated 10 coatings every other week, so in one year that was about 250 variants on a given film product. I've processed from 68F to 120F as well during these studies. I believe that the Ross paper expresses the true situation.
I have seen no definitive or authoritative references to the contrary. This is particularly true when as you say, and as Mark Antony says, it is a 3D effect. You need cross sections to prove the point.
Okay, so what the disagreement revolves around is "apparent grain clumping" vs "actual physical grain clumping"? As far as boiling the film in hot developer - that is one thing, but what happens to the gelatine structure when temperature goes haywire? Does the silver still stay where it is?
If Ross made this experiment in the 1920s - does it still hold value? Does the active versus inactive gelatine have any impact on the issue?
Prints reveals truths that negative scans obscures.
Ok but now we have "Grain" "Granulairity" and "Grainyness" and "root mean squared granularity" in that last post. We probably need specific definitons of those and how they are measured to continue.
Can we agree in the discussion that "Grain Clumping" means the net movement of silver in the emulsion in a "grain-centric" direction, independent of any stocastic movement.
We need to agree on what constitutes movement also.
If a "grain" were to gain silver mass on one side and lose silver mass on the opposide side, the grain's center of mass has moved but the molecules in the grain have not moved.
It's fascinating that in study of image structure, the study of graininess, sharpness, acutance, contrast... namings and definitions are not easy, and so, discussion is not easy. Like much in photography, those definitions and names are a can of worms.
Originally Posted by Mark Antony
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Hmmm ... Mark Antony's image does indeed look quite like a can of worms. Maybe we should refer to such appearance as "worminess" rather than calling it clumping, since "worminess" refers just to an observed appearance, and does not impute a movement or process to create that appearance as "clumping" does. It is useful to try to tease out metrics that are as independent as possible to try to sort out root causes.
If gelatin does not move, then the silver does not move by more than about 2 microns according to the work of Ross. He used either Formalin or Chrome Alum as hardener, probably the latter as it is preferred on glass plates. Since astronomers still use plates to some extent and routinely check star positions, I would say that the work is still valid. I know that a Kodak research worker was assigned to the observatories in AZ for several years during the 70s checking out this type of work.
That said, if gelatin moves, then silver moves with it and relative to the gelatin movement. I have actually caused blisters in films and papers and have been able to lift the emulsion from the support and view the image. BTW, Kodak sold "stripping films" that did exactly this and remained intact for transfer to another support. The stripping was normally carried out at 100F.
All grain is typically reported as RMSG. It is accompanied in many cases by photo micrographs down through the film and with cross sections to show the grain pattern. I have posted examples of both in my OP. It is critical to understanding this that silver takes many forms due to development conditions and grain type and these appear different to the eye and appear different when measured by an instrument.
That said, if gelatin moves, then silver moves with it and relative to the gelatin movement.
PE
That's the theory and practice in most cases.
When it goes wrong you used to get full reticulation with most typical films (up until the late 60's), with modern hardening few films have issues, but apart from the relatively unhardened EFKE films which aren't remotely typical there's a small number of films are prone to issues.
Stripping films work in a different way with an unhardened subbing layer and a hardened emulsion.
There's some crossed thoughts in this thread because Ron's original post support the practicalities that with modern (available) film developers it's not temperature or pH themselves that affects grain (& grain clumping).
What's also confuses is the term Grain clumping has been historically used to cover more than one type of large/excessive grain seen in practice.
What is known is that with full blown reticulation there is Silver migration (Mason et al) where little work has been published is the stages prior to full reticulation, but we know it exists.
It reminds me of my Virology lectures at University in the mid 90's when our lecturer (an eminent virologist) told us they knew cervical cancer was often caused by a virus, but they had no proof, that took another 20+ years.
In the case of micro reticulation/grain clumping companies know why it happens so why pour research money into it, they already have a cure . They improve film hardening instead.
However for other reasons, possibly to get better film speed and other characteristics etc both Kodak & Fuji make 400 ISO films that are significantly less well hardened. These are the films that show the most micro reticulation.
I posted an RMSG plot earlier to show the variations introduced by differences in development time.
To back this up further, here are some actual grain pictures taken from Haist (with permission BTW)
From left to right
1. Early stage development
2. Late stage development
3. Using a physical developer
4. Using a straight chemical developer
In like manner, the appearance of the grain varies substantially as a function of pH, time, temperature and Grant goes on to add that it also varies as a function of exposure type such as bright short exposures vs dimmer long exposures.
And, what is missing in this is that there is a 3D or X-Y-Z component to the image so what you see in these 4 photos are 2D representations of a 3D world more clearly shown in the original post in cross sections.
So, back to these micrographs - you cant tell me that your eye would not see a difference in grain. You are basically seeing under and over development and two different developers. And the result is a huge change in the grain structure, but absolutely no movement of silver beyond perhaps, what Ross reported! And, there are no literature references to "micro reticulation" beyond some scattered statements of individuals trying to explain changes in their negatives which can easily be explained by this post. Adding a 3D component takes us back to the example in the OP where we see stacks of these grains, not clumps.
Adv Reply
Originally Posted by Photo Engineer
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. They improve film hardening instead.
