film vs digital

[D&A]

The article in the linked page concludes--->"These results meet the macro-pheomena: Professional film, positive film and low ISO film show smoother grain and vice versa"

I almost want to say "duh"....one doesn't need electron microscopy to evaluate and come to this conclusion . I think this fact was well established before electron microsopy was even in existance. (I just couldn't resist...LOL!)

Dave (D&A)

 

[Leigh]

+1 Yup.

Except I don't know what a pheomena is.

- Leigh

 

[Shashin]

Originally Posted by Shashin
There is no grey, only black or white. If course these grains often do not cover 100% of the area but occasionally can approach 100% coverage. Lets say they do, and lets say we take a sample of 10 microns on a side. That sample will only contain roughly 100 crystals and can have only 100 different levels of transmission.

Invalid assumptions.

You're neglecting the depth of the emulsion and the orientation of the grains.
Both factors can dramatically increases the number of possibilities.

I went through an exhaustive study of this effect on a product that I designed a few years ago.
It counted microscopic particles in a fluid, which flowed through a sensor array.

The methodology was quite simple for low densities of particles, but became much more complex when the concentration exceeded about 10% of the presumed maximum, which itself was not nearly full saturation.

- Leigh

I did not post what you are quoting. I am not sure why particles flowing through fluid is very relevant.

BTW, what is the depth of a standard photographic emulation? I would love to know because the film companies don't publish that data. Most people only know the base thickness which is far greater.

 

[Leigh]

My comments were not directed at you; they were for Bob.

The distribution of particles in a fluid is absolutely relevant, since that's exactly what you have when an emulsion is coated, before it dries. After it dries, it just freezes the particle distribution.

I too would like to know the emulsion thickness. I don't have that information.
You could easily find out by removing the emulsion from half a sheet of film, then measuring the thickness of both areas.

Also, I'd like the definition of a micron in this context. It's used in various disciplines to mean either one millionth of a metre or one millionth of an inch. Two very different sizes.

- Leigh

 

[Shashin]

Well, I took this morning. It is a section of color negative film. Emulsion to the bottom. 50x objective with DIC.

Here is a 10um overlay. I work in SI units and so that is a real micron of one millionth of a meter (0.001mm). The grid is 0.01mm squares. (What is an inch? And who defines a micron in relation to one? Certainly not scope manufacturers--electron or otherwise)

This is from the developed leader and so I don't know how much swelling is going on--it certainly has an unusual density as it was completely exposed to light. Nor do I know how the cutting machine has deformed the emulsion. Still, with three color layers and an integral mask, it is not very thick--20um or less. I would imagine B&W emulsions are thinner.

 

[Bob]

Very cool.
I was furiously looking for data on film emulsion thickness and found only one source for radiographic film which was listed as 10 microns(metric)
I am guessing that the cross-section you have posted looks roughly like about a 20 micron thickness but we know that color negative film is often coated in at least 4 layers (three color and one usually thinner yellow filter).
So unless we have more data, can we assume that the emulsion layer is on the order of 5-10 microns? I seem to recall this figure although I have misplaced my old copy of Mees and James.
Also, can we assume that the emulsion consists of approximately 40% silver halide and 60% binder (from memory)
I unfortunately predate tabular crustal emulsions which seem to be pretty popular, but it appears to me that these are roughly 1 micron across the base. I do not have a good reference for their thickness.
The next step might be the estimation of the number of such grains in a volume of emulsion at nominal thickness and some area we might agree as that which effectively is a perceivable unit of area.
For sake of argument, perhaps we have an enlarging factor of perhaps 2 (approximately a 4x5 negative enlarged to an 8x10 print) to 8 (35mm frame's 24mm enlarged to 8 inches).
Final print observable minimum feature size of lets say 85 microns (300 per inch converted to SI) which gives us a film "observable unit" from say between 42 microns on a side for 4x5 and 11 on a side for 35mm.
Anybody have better data for these assumptions?
thanks
-bob

 

[Leigh]

The term micron, defined as a millionth of an inch, was used in the machine tool industry at least 100 years before the SEM was invented.

- Leigh

 

[Bob]

The term micron, defined as a millionth of an inch, was used in the machine tool industry at least 100 years before the SEM was invented.

- Leigh

Maybe so, but the SI version seems to be the one most used today in photographic and scientific applications.
-bob

 

[Leigh]

Hi Bob,

I don't disagree. SI units are certainly common in contemporary scientific usage.

But back when coating machines were invented, they were built by an industry that used inches, and micro-inches (microns).

- Leigh

 

[Bob]

Hi Bob,

I don't disagree. SI units are certainly common in contemporary scientific usage.

But back when coating machines were invented they were built by an industry that used inches, and micro-inches (microns).

- Leigh

LOL we were using SI back in 1967 when I used to do this.
-bob

 

[Shashin]

Maybe so, but the SI version seems to be the one most used today in photographic and scientific applications.
-bob

A little clarification--the ONLY definition used in scientific and photographic applications today and for a long time before now--micrometre is the actual term but micron has been in use since 1876 or so. And no offense to the machinists I know that still work in inches. (I would really like to know who was making one millionths on an inch cuts or holes 100 years before the SEM. ) I think you will find a micron (or mil) in engineering referred to 1/1,000th of an inch, which is 24.5um.

 

[Bob]

A little clarification--the ONLY definition used in scientific and photographic applications today and for a long time before now--micrometre is the actual term but micron has been in use since 1876 or so. And no offense to the machinists I know that still work in inches. (I would really like to know who was making one millionths on an inch cuts or holes 100 years before the SEM. ) I think you will find a micron (or mil) in engineering referred to 1/1,000th of an inch, which is 24.5um.

Yup, micrometer is correct, but colloquially an awful lot of folks call them microns as in a 5.5 micron pixel pitch.
-bob

 

[Shashin]

I know, every scientist I work with uses "micron." "Micrometre" pegs you as a geek.

 

[Bob]

I know, every scientist I work with uses "micron." "Micrometre" pegs you as a geek.

ok, perhaps µm but I keep forgetting my keyboard shortcut for it.
-bob

 

[Shashin]

Very cool.
I was furiously looking for data on film emulsion thickness and found only one source for radiographic film which was listed as 10 microns(metric)
I am guessing that the cross-section you have posted looks roughly like about a 20 micron thickness but we know that color negative film is often coated in at least 4 layers (three color and one usually thinner yellow filter).
So unless we have more data, can we assume that the emulsion layer is on the order of 5-10 microns? I seem to recall this figure although I have misplaced my old copy of Mees and James.
Also, can we assume that the emulsion consists of approximately 40% silver halide and 60% binder (from memory)
I unfortunately predate tabular crustal emulsions which seem to be pretty popular, but it appears to me that these are roughly 1 micron across the base. I do not have a good reference for their thickness.
The next step might be the estimation of the number of such grains in a volume of emulsion at nominal thickness and some area we might agree as that which effectively is a perceivable unit of area.
For sake of argument, perhaps we have an enlarging factor of perhaps 2 (approximately a 4x5 negative enlarged to an 8x10 print) to 8 (35mm frame's 24mm enlarged to 8 inches).
Final print observable minimum feature size of lets say 85 microns (300 per inch converted to SI) which gives us a film "observable unit" from say between 42 microns on a side for 4x5 and 11 on a side for 35mm.
Anybody have better data for these assumptions?
thanks
-bob

As far as I know, emulsion and coating thickness has been a closely guarded secret. I have found very old references to it, but are usually vague and are certainly referring to old emulsion and no T-grain technology.

My question would be how important is this information anyway? Couldn't you get the answer from a simple densitometer? Not in terms of individual grain, which I think is not very useful, but simply the efficiency of the emulsion to pass/reflect light. You should then be able to scale to area? Perhaps not. Not sure.

Although, right now, I can't remember what the actual question was.

 

[Shashin]

If I find an old B&W neg or print, I will put it under a microscope.

 

[Jorgen Udvang]

I think you will find a micron (or mil) in engineering referred to 1/1,000th of an inch, which is 24.5um.

1/1,000th of an inch? You got to be joking. Inches were dumped by all but one industrialised country very, very long ago and doesn't translate to scientific measurements easily.

A micrometre is one-millionth of a metre (or one-thousandth of a millimetre, 0.001 mm, or about 0.000039 inches). The term micron and the symbol µ, representing the micrometre, were officially accepted between 1879 and 1967, but officially revoked by the ISI in 1967. It's still in use in some English speaking countries though.

 

[Shashin]

1/1,000th of an inch? You got to be joking. Inches were dumped by all but one industrialised country very, very long ago and doesn't translate to scientific measurements easily.

That is in engineering. And in the US. And no, not much use in the sciences.

 

[D&A]

From what I recall reading many years ago (and for me "recall" is a relative term for me personally...LOL)...B&W emulsion is on the order of 10 microns give or take, greatly depending on the film stock. Just as Bob (and others) estimated.

Shashin, very cool and yes, the whole world (especially the scientific community) works in metric . Just don't ask me why I have a couple of "english measurement" rulers in the draw next to me...LOL.

Dave (D&A)