Wow - read this re: Film versus Digital debate!

[tonybrown]

This thread must be a record. Interesting, though. A couple of thoughts - 1) in digital it is very difficult to accurately reproduce a deep red colour - but not impossible. I spent time this summer capturing and printing a deep red rose. The printing part was the most difficult and following my usual process gave me rather purple reds. However, reducing the luminance of the reds and oranges while increasing the saturation gave me the desired result. My camera a 1DsmkIII and printer i9900. In my view the primary problem is that a simple 3 colour RGB representation (Adobe RGB) cannot represent everything the camera tries to capture (or what my eye sees) - and incidently this also applies to images scanned from film and represented by the RGB format. 2) The role of the photographer is more important than the camera or the medium. Digital has enabled me to rapidly grow on the photographer's learning curve largely because I have more control over the process and experimentation does not cost me a bean. With over 50 custom functions on a 1DsmkIII there's lots of room to go wrong - but also lots of room to combine serious science with art ... and I'm a scientist. Regards to all ... it was an interesting read.

[rich_evans]

Well I'm posting some micrographs that I took today, and I'll try to be as specific as I can as to the prep and imaging fundamentals, so that the visual information can be used as a basis for one side of this discussion or the other. I can't quite rationalize what I'm seeing but I'm certain that they'll be any number of valid explanations.

 

The first set is a series of light optical micrographs taken with a NIKON Eclipse LV100POL microscope equipped with 4, 10, 20, and 40x strain free POL med. NA (numerical aperture) objectives. The image capture software was OLYMPUS analySIS.

 

Sample was from a small section of very old Plus-X film - the image was originally tree branches so there is some variability in the density. The film was mounted emulsion side up on a pre-cleaned glass microscope slide, immersed in 1.550nD oil, and covered with a 0.15mm coverslip. Note that film's emulsion does not present the actual 'grains' at the surface - the grains are actually trapped in a gelatin or gelatin/latex matrix which is (usually) laid down on a polyester base. (This became problematic when attempting to image the grains with the scanning electron microscope as shown later.) So there is some thickness and therefore a depth-of-focus issue when imaging the tiny grains. At any given point of focus, some grains will be in focus and present a totally absorbing feature, others will be slightly out of focus and present a small dark halo - this is normal when observing features (especially this small) and is referred to as a becke line.

 

The images were taken at 40x, 100x, 400x magnification at the sensor (used to be called the 'film plane') - actual magnification is dependant upon the size of the final image (screen/print/projection). However - the most important thing in any micrograph is the micron marker. Images were obtained using transmitted plane polarized light - the microscope is always perfectly aligned as per Koehler illumination.<div></div>

[James G. Dainis]

This whole thing seems to be about nothing but semantics. In common usage, binary refers to files contain

formatting information that only certain applications or processors can understand. I can look at a roll of film

(analog) and see images; I look at a CF memory card (binary) and see nothing. If you need a computer or

application to interpret it, it's binary.

[rich_evans]

Next up - the SEM images. (This is mostly only for those interested in the technical aspect of how the images were

obtained - but read on if you like)

 

This is the same piece of film however because the 'grains' (let me call them features) are trapped in the emulsion, the

scanning electron microscope (SEM) can't 'see' them. The SEM only images surfaces. Unlike the light microscope

images, which are generated by passing light through a material, the SEM generates images by collecting electrons

which are emitted from a surface, typically only from a depth of 0.5-3 microns. Sample was coated with approx. 50

angstroms of gold for conductivity. The instrument and parameters are as follows: Zeiss Supra 55 field emission SEM,

10kV accellerating voltage, 10mm working distance, probe current of 400pA. Note the scale bars in each image.

 

So the features were not on the surface. I scanned around and found a few 'discontinuities' or damaged/scratched

surfaces and was able to find some exposed particles by using a backscattered electron detector. This detector is able

to image differences in the elemental composition of materials - low atomic number materials are 'darker' grey and higher

atomic number materials are 'brighter' by comparison - this type of image is sometimes called atomic number contrast.

So because the silver is of a higher atomic number than the surrounding organic matrix of gelatin/latex, any particles

should show up as bright areas on a dark background with this detector. The composition was confirmed by x-ray

spectroscopy - interestingly the only element found was silver (you'll see gold in the spectrum later and this is artifact

from the sample prep).

 

The backscattered electron detector has the disadvantage of lower resolution by about a factor of 10, so while the sample

of interest was found, the clarity, or resolution, was less than I had hoped - the best I could manage was about 100.000x.

Once the features were located, the higher resolution secondary electron detector was used to obtain the second image

in this sequence. You'll note the much better resolution even at this high magnification (220,000x).

 

What's interesting is that the apparent individual 'grains' that we think we see in the light microscope images are actually

agglomerates or clumps of much smaller crystals.

[rich_evans]

SEM Images..............repost attempt.........<div></div>

[rich_evans]

And finally - just to muddy the waters a bit more, a number of years ago, when Kodak came out with TMAX 400, I thought

it might be fun to try to image the individual crystals of the emulsion with the SEM, since Kodak was marketing the new

technology as a breakthrough in their emulsion and halide growing expertise. At that time, I had found a way to disolve the

gelatin emulsion from the unexposed film base (and which I have since not be able to find) and got this really neat image

of a single crystal. For what its worth............<div></div>

[vijay_nebhrajani]

Rich, thanks for the images. Amazing.

 

I only have questions at this point; not the argumentative variety - just the "I want to know" variety.

 

1. In the 400x optical picture, I see ring-like structures that are most visible in the white areas. What are those?

 

2. Can you go higher optically? Like 1000x or more?

 

3. Is it possible that because of the bright light the dynamic range of your image capture is exceeded so the

silver appears black? Could you overexpose progressively to see if those black grains lighten? I mean truly

opaque grains shouldn't lighten with greater exposure, should they?

 

4. In the SEM images, especially in the 102x one, it appears like there is a cavity surrounding the silver,

almost as if a silver halide crystal was present that is now gone, but has left that silver deposit behind. Is

this a correct interpretation, or is it just random gelatin goo?

 

5. Would any structure made up of opaque silver grains separated by gaps smaller than the wavelength of visible

light be completely opaque to visible light? Would the size of the grain matter or would only the gaps that are

smaller than 400 nm?

[James G. Dainis]

I now know what a single crystal looks like. I thank you for that. Can you now show me what a binary 1 or 0 looks like?

[vijay_nebhrajani]

Rich - another thought: how would that 20 angstrom sputter coated gold film look under a 400x optical microscope? What if we could make it 500 angstroms thick?

[danielleetaylor]

Rich,

 

Thanks for the microscope views. They offer no surprises, to me any way.

[danielleetaylor]

<P>Vijay,</P>

<P></P>

<P><i>The first statement puts a lower size bound on grains - 0.2 microns - a size easily detected by an optical

microscope (even if it were a bit fuzzy - here's the reference).</P>

<P></P>

<P>The next statements imply that the smallest developed grain is not even detectable by an optical microscope -

much smaller than 0.2 microns then.</i></P>

<P></P>

<P>If I didn't make this clear, everything I said was in reference to the 400x photo in the same post. See the

scale next to it. You would be hard pressed to see or notice a 0.2 micron grain at 400x. Most of what you see in

that photo is clumps of grains, not individual grains. That's the nature of film grain, to clump together into

larger sections based on exposure.</P>

<P></P>

<P>You are so bent on trying to win this argument that you can't see the forest for the trees. You nitpick every

single thing that is said. I feel like I'm dealing with a lawyer and I have to triple check every statement I

make. I'm afraid at some point I'm going to have to declare that it all depends on what "is" is.</P>

<P></P>

<P><i>You changed the definition of grain on me there didn't you?</i></P>

<P></P>

<P>A single deposit of silver left over from the development of a single silver halide crystal.</P>

<P></P>

<P><i>Ha. You imply that observation is the ultimate truth. Yeah right; we observe daily that the it is the sun

that rises and sets, yet this is a heliocentric planetary system.</i></P>

<P></P>

<P>Vijay, you claim that there are individual gray grains, that tone is formed within a single silver deposit

from a single grain based on filaments which have to be imaged under an electron microscope.</P>

<P></P>

<P>It is <i>on you</i> to explain why we never observe gray grains. Even if they could theoretically exist, they

are so rare that Ansel Adams, after studying film, described B&W film tone as a halftone process. Either he never

saw them, or saw so few that he determined they do not contribute anything significant to formation of tone. I've

studied at least a dozen different B&W frames under a microscope and I never observed a gray grain. Michael

Reichmann doesn't seem to think they exist. The clumps are there or not, unlike pixels which are there in any one

of thousands of tones (before Bayer interpolation; millions after).</P>

<P></P>

<P>I really think you are suffering from an emotional bias in this debate. You want film to "win". This isn't

about "winning" or "losing". It's just the nature of their image structures.</P>

<P></P>

<P><i>Your observations could be flawed simply because you are seeing bright light through a microscope which

might be exceeding the dynamic range possible for your eye, meaning that gray could appear black.</i></P>

<P></P>

<P>Which explains why I see gray tones and colors when using a prepared slide of a specimen :-/</P>

<P></P>

<P>To do anything meaningful with B&W film you must project a light from behind it. This is how enlargers and

scanners work. Silver is opaque. It's not translucent or transparent, it's opaque. Therefore the device which

"sees" the film opposite the light, whether a human eye or CCD or traditional photo paper is going to "see" black

specks on clear base. Silver is what it is. It's not glass or diamond. It's silver. Opaque.</P>

<P></P>

<P><i>You'll have to do better than that if this is your idea of "experimental evidence". When you show me some

incontrovertible experimental evidence, I'll think about bending the theory. No sooner.</i></P>

<P></P>

<P>This from a man who has no evidence what so ever to back his theory. Ansel freaking Adams called B&W film a

halftone process, exactly what I am saying in this thread. That's enough for me. When you observe and record gray

grains, let me know.</P>

<P></P>

<P><i>That is quite absurd. You imply that as soon as the size of a grain becomes less than some threshold it

won't be optically observable, but clusters of these will block light just fine, i.e., work just fine as an

optical attenuator.</i></P>

<P></P>

<P>That's how things work when you're dealing with clusters of an opaque material where sizes are at the

threshold of either A) the resolving power of the recording device; or B) the threshold of visible wavelengths.</P>

<P></P>

<P><i>This means that if I ever make a film with really fine grain - smaller than 0.1 microns even - I must keep

those grains more than 0.4 microns apart, somehow, because otherwise the film simply wouldn't pass light as soon

as those grains developed - to any size. And yet, if I did manage to clump them close enough so that they formed

a super granular structure, they would start passing light again, tones would reappear, and everything would be

fine again.</i></P>

<P></P>

<P>You're thinking yourself into circles and coming back with conclusions not supported by anything your

opponents have said.</P>

<P></P>

<P><i>Daniel, every time you come up with a theory of what may be happening, I come up with the absurdities it

causes.</i></P>

<P></P>

<P>I've had the same exact theory from my first post. The only thing I modified was that I incorporated the fact

that silver deposits grow in size in relation to exposure and development time. The theory does not cause any

absurdities what so ever. The only absurdity in this debate is that you insist something exists and meaningfully

contributes to perception of tone when said thing has never been observed by you, me, Adams, Reichmann, etc.

Where are these gray grains if they form the basis of tone in B&W materials? We would have to see them on every

frame. But we don't see them at all.</P>

<P></P>

<P><i>Won't you come around to accepting that a single grain must act as a light attenuator by itself, i.e., not

be binary - clear or opaque?</i></P>

<P></P>

<P>Can you find any reference in any literature to transparent or translucent silver?</P>

<P></P>

<P><i>And yet Rich Evans provided an example of a 20 angstrom gold film sputter uniformly coated with gold</i></P>

<P></P>

<P>We're not dealing in angstroms Vijay, we're dealing in microns. As you can clearly see in my microscope views

and Rich's microscope views, silver is opaque at the scale of optical enlargement of a B&W frame.</P>

<P></P>

<P>What is a theory of the physical world apart from observation to support it? Faith. I'm not against faith, but

between faith that there are gray grains and observation that there are not, I'll go with observation on this

one. I've read no religious text that insists God told man grains are like pixels, and I know of no religion

which insists that I believe B&W silver grains are just like pixels. So I have no reason to even examine the

possibility that I should have faith in gray pixels.</P>

 

[rich_evans]

Vijay - answers:

 

1- the rings you see are as I tried to explain (maybe not too clearly) in the description of the optical images.

Because many of the smallest particles are in a different plane of focus, an effect called the Becke Line occurs -

this is a dark (or light) ring around a given feature which moves into or out of the feature as focus is raised or

lowered. What you are seeing is that phenomenon.

 

2 - the depth of the emulsion becomes problematic with increasing magnification because the particles are

scattered at various depths throughout. As magnification increases, DOF decreases and fewer particles will be

in sharp focus. In addition, resolution is a factor of many things including what is known as MUM - Maximum

Useful Magnification - a point beyond which further optical resolution is impossible. This is determined by the the

numerical aperture (NA) of the objective used times 1000 (1000 x NA) - the NA of the objective I used was 0.65.

Magnifications higher than this value will yield no further useful information or finer resolution of image detail, and

will usually lead to image degradation. In addition, excessive magnification introduces artifacts, diffraction

boundaries, and halos into the image that obscure features and complicate interpretations.

 

I will give it a shot on Monday when I get back to work and we'll see what we get.

 

Ditto for items 3 and 4 - although if there were any other elemental contribution it would have shown in the x-ray

spectrum (which I didn't get a chance to post - that will also have to wait until Monday).

 

5 - I don't know.........

 

--Rich

[danielleetaylor]

<P><i>So to form say the equivalent of a digital pixel, which has 2^16 tones for just one color, you'd need (2^16 - 1) binary film grains; or 65,535 grains. The film pixel that this would form would occupy an area of 256x256 binary pixels, or at a 2 micron grain size, an area in the neighborhood of 500 microns x 500 microns, or 0.5mm x 0.5mm.</i></P>

<P></P>

<P>1) You're out thinking yourself again. Most grains are smaller than 2 microns, though they often clump to larger than 2 microns. They vary in size and clumping patterns and occur in 3D space which all affects the number of tones which can be rendered within a given space. You'll never find a precise count for a precise area because film is not uniform, and there's no easy way to compute what can be produced using grains of varying size and clumping patterns in a 3D stack.</P>

<P></P>

<P><i>By this reasoning, of course a color film pixel would be nearly 1mm x 1mm assuming dye clouds are roughly as small as silver halide grain. Of course, if the dye clouds were bigger, the film pixel would be even larger.</i></P>

<P></P>

<P>Dye clouds are roughly 3-10 microns, but they're also translucent and randomly stacked in 3D space within each layer, with a minimum of 3 layers. Within one layer two dye clouds could overlap and will produce a darker color than one by itself. Three would be darker still. Two dye clouds could just be touching and their thin edges could be perceived as some lighter tone. Multiply this interplay by 3 layers. A single dye cloud is not like a pixel, able to take on any of millions of colors. But the random arrangement we see in color film makes for a very efficient dithering mechanism. You don't need nearly as much area as you might think to be able to render millions of colors. I would guess the area would be larger than today's DSLR pixel sizes, but not by much.</P>

<P></P>

<P><i>So then, in B&W chromogenic film, the image is formed by transparent, or rather, grayscale dye clouds. So one dyecloud (maybe somewhat larger than a traditional silver grain) - must be capable of representing continuous tone. So the resolution of chromogenic (C41) B&W film must be orders of magnitude better than traditional silver halide film, right?</i></P>

<P></P>

<P>No, because there's not that much potential variation of tone within a single dye cloud, and dye clouds are, on average, much larger than grains.</P>

[danielleetaylor]

<P><i>3. Is it possible that because of the bright light the dynamic range of your image capture is exceeded so the silver appears black? Could you overexpose progressively to see if those black grains lighten? I mean truly opaque grains shouldn't lighten with greater exposure, should they?</i></P>

<P></P>

<P>No, they should not.</P>

<P></P>

<P>But let's say, for sake of argument, that you did find a gray grain on overexposure (which was not caused by a halo effect). Or heck, let's say someone posts a microscope view at normal exposure where we find a gray grain. Let's go even further as I did earlier and propose a machine that could deposite a silver grain so precisely that half its surface area consisted of gaps capable of passing light, a gray grain.</P>

<P></P>

<P>Would any of this mean that tone in B&W film is formed by gray grains which are like pixels in their ability to represent thousands of distinct tones?</P>

<P></P>

<P>Nope.</P>

<P></P>

<P>One of the key things you're missing is that for all practical purposes, you lost this debate a long time ago. Even if it were demonstrated that a gray grain could exist or does occasionally exist, it clearly does not exist any where near the frequency necessary to be a significant component of B&W tone rendition. Grains do not magically turn gray under the light of an enlarger as one can verify with a grain focuser or a really big print. We're looking at two frames of B&W film at 400x and the gray in those frames is clearly formed by black clumps of opaque grain mixed with clear base. No gray grains contribute to their image structure.</P>

<P></P>

<P>I just don't understand why you're hung up on this. What would convince you? More microscope views?</P>

<P></P>

<P><i>5. Would any structure made up of opaque silver grains separated by gaps smaller than the wavelength of visible light be completely opaque to visible light? Would the size of the grain matter or would only the gaps that are smaller than 400 nm?</i></P>

<P></P>

<P>If you could manage to "push" light through a hole in photographic silver deposits smaller than its wavelength then you would literally have the basis for a scientific paper. There are examples of electromagnetic radiation passing through holes in an opaque material smaller than said radiation's wavelength, but they are rare, special cases currently being studied. (The working theory is that the radiation doesn't actually pass through, it excites electrons in the material which emit the same wavelength of radiation off the other side.) Again, stand in front of your microwave. Put your hand right on the glass. The reason you do not burn is because the wavelength of microwaves generated is too large to pass through those holes. </P>

[emraphoto]

"My favourite photographer, Perou, still shoots primarily on film, unless requested otherwise. There has to be a reason why

so many pro's stick to the medium..."

 

in the last two years of shooting news service i haven't seen a single film camera amongst the fellow rabble. please do not

mistake this as anything more than my observation. i happen to like film, don't work on it but have fond memories...

[philip_sutton]

Yes guys I am sitting here having a chuckle to myself. I did not know when I penned my question that we would be

setting some kind of a record. Does this make me famous?? I hope the moderators aren't abusing me or

something?

 

As mentioned in my second comment at the top - the only experience I have with forums like this, is on my two

traditional archery sites. A debate like this (long-winded, contentious), would have been pulled by the moderators

long ago. I am not saying that is a good thing - in fact hail to those in charge here for letting a healthy debate run its

course.

 

In fact I am sure that the main antaginists here (you all know who you are - LOL) will either be about to be divorced

by their spouses, need to go and see their optitions for a new prescription, be getting the sack at work for being so

tired and mind fatigued, or have elevated cholesterol for sitting at the computer for so many hours. In other words -

whether this thread is pulled or not does not matter - these blokes will be falling like flies shortly and this thread is

about to die out!!

 

All jokes asided - may I please ask a serious question.

 

Can one of you scientist dudes please write a summary for the rest of us plebs. I have tried reading this all through

from the top and it is just too daunting. Can you please summarise what conculsions we have reached - otherwise

(for the majority of us) whis whole thing has been pretty pointless.

 

Please say whether film is still up there with digital (I mean comparing my 67ii pentax, scanned on a high quality

home scanner like a Nikon 9000), not for pro's running to time constraints, but to the serious ametour like myself.

 

I hope this does not open up a whole new can of worms??

 

Go on guys - knock yourselves out!!

 

Phil

[bernardwest]

<i>In fact I am sure that the main antaginists here (you all know who you are - LOL) will either be about to be divorced by their spouses, need to go and see their optitions for a new prescription, be getting the sack at work for being so tired and mind fatigued, or have elevated cholesterol for sitting at the computer for so many hours.</i><p>

 

You've got that one right....<P>

 

<i>Can one of you scientist dudes please write a summary for the rest of us plebs. I have tried reading this all through from the top and it is just too daunting.</i><p>

 

Check out Rishi's post from Nov 14th 2.31am. I found this to be really helpful to me in understanding how the process works.

[danielleetaylor]

<P><i>As mentioned in my second comment at the top - the only experience I have with forums like this, is on my

two traditional archery sites. A debate like this (long-winded, contentious), would have been pulled by the

moderators long ago. I am not saying that is a good thing - in fact hail to those in charge here for letting a

healthy debate run its course.</i></P>

<P></P>

<P>This has been a civil debate. I feel bad for being sarcastic with Mark, but I was just annoyed with the

microscope misunderstanding. He pressed pretty hard for someone who had never tried it. Other than that, I can't

think of any reason why a moderator would want to kill this. We haven't been at each others throats or anything.

I would buy Vijay a beer if we lived near each other.</P>

<P></P>

<P><i>In fact I am sure that the main antaginists here (you all know who you are - LOL) will either be about to

be divorced by their spouses, need to go and see their optitions for a new prescription, be getting the sack at

work for being so tired and mind fatigued, or have elevated cholesterol for sitting at the computer for so many

hours. In other words - whether this thread is pulled or not does not matter - these blokes will be falling like

flies shortly and this thread is about to die out!!</i></P>

<P></P>

<P>Priorities man. What is a marriage or a job in the face of a discussion about the nature of the interaction of

light with silver grains on B&W film? ;-)</P>

<P></P>

<P><i>Can one of you scientist dudes please write a summary for the rest of us plebs. I have tried reading this

all through from the top and it is just too daunting. Can you please summarise what conculsions we have reached -

otherwise (for the majority of us) whis whole thing has been pretty pointless.</i></P>

<P></P>

<P>I thought the thread was over with Rishi's excellent summary. Search for Rishi Sanyal , Nov 14, 2008; 02:31

a.m. His message pretty much sums things up, though apparently Vijay still disagrees regarding whether or not

individual grains contribute in a meaningful way to tonality.</P>

<P></P>

<P><i>Please say whether film is still up there with digital (I mean comparing my 67ii pentax, scanned on a high

quality home scanner like a Nikon 9000), not for pro's running to time constraints, but to the serious ametour

like myself.</i></P>

<P></P>

<P>For the most part this has not been about whether or not film was "up there" with digital. To decide that you

have to shoot an identical scene with your film equipment and digital equipment, process using your work flows,

and evaluate using your final prints. The variables at each step are too large for a single theory as to which is

"up there". Either medium is capable of excellent results with good equipment and technique. I will say that

unless there's a serious flaw in your equipment or work flow, a 6x7 system should be capable of excellent

results, competitive with the results of very high end digital equipment, so use it without reservation. Your

image quality will rest on your imagination and technique, not your choice of digital or film.</P>

<P></P>

<P><i>I hope this does not open up a whole new can of worms??</i></P>

<P></P>

<P>Please, no debates about whether or not worms are opaque or translucent ;-)</P>

[danielleetaylor]

philip,

 

Going back to your original post I would have to say that I sometimes agree with Ken, sometimes disagree. I'm not

going to go point by point and say where I disagree with the linked article. It's not worth it. Your Pentax 6x7

is capable of excellent results. Enjoy it. Add a DSLR (if you don't already have one) at some point and enjoy it to.

 

I think the fact that the film market has become smaller has created too much insecurity among people who, for

whatever reason, continue to shoot film. While I find the technical differences interesting, and have my own

opinions on the strengths and weaknesses of each, I can't say that digital or film has ever been the deciding

factor in a photograph which impressed me. As I look at images in museums, in galleries, at photo club meetings,

on the Internet, etc., digital or film is never the thing which makes the image impressive. It's the imagination,

technique, and vision of the artist behind the image.

 

Having said that, Canon images always look much better than Nikon images ;-P

 

(Yes, I was kidding with that last sentence.)

[philip_sutton]

Wow - thanks Daniel and Burnie - a nice summary. I will check out what Rishi wrote - thanks

 

Phil

[rich_evans]

This has definitely been one of the most civil and interesting (at least to me and a few others) debate that I've experienced on ANY forum on any site. The banter has been mostly intelligent and thought out, not necessarily abusive, and if nothing else, educational as to content and process. I commend you all.

 

Phil - thanks for opening the 'can of worms' - its been fun. I for one will continue in MY quest of obtaining some kind of meaningful data that may help others.

 

And I'll continue to shoot both film and digital.

 

Now if only I could find a digital sensor that I'd be willing to sacrifice for some kool SEMs of the sensor surface.......................

[rishij]

Vijay: <i>"This means that if I ever make a film with really fine grain - smaller than 0.1 microns even - I must keep those grains more than 0.4 microns apart, somehow, because otherwise the film simply wouldn't pass light as soon as those grains developed - to any size. And yet, if I did manage to clump them close enough so that they formed a super granular structure, they would start passing light again, tones would reappear, and everything would be fine again.

<p>

Daniel, every time you come up with a theory of what may be happening, I come up with the absurdities it causes."</i>

<p>

It would make me so happy, Vijay, if you just quit using the word 'absurd' and all its derivatives. It's really annoying, especially when your absurdities are not absurdities at all. It makes you sound so self-righteous. Your analysis above is bunk. When you say "if I did manage to clump them close enough so that they formed a super granular structure, they would start passing light again, tones would reappear", realize the grains aren't actually moving. They're already in place. The 'clumping' occurs because of filamentous growths adjacent to one another (whether they are on the same crystal or not) start running into one another or getting really close to one another (but still always separated by gelatin if on different grains) such that when viewed at lower magnification, appear as a solid black clump. Less-than-black is created when <i>either</i> subgranular spaces do not have filamentous growths (just clear film base) or super-granular spaces, i.e. a bunch of portions of adjacent crystals, do not have filamentous growths because these areas were not exposed. So, in your example, a clear space would be defined as a bunch of your 0.1 micron grains that remained unexposed + the gelatin separating them. This would lead to an area of lighter tones. What's so absurd about that?

<p>

Furthermore, you write: "Won't you come around to accepting that a single grain must act as a light attenuator by itself, i.e., not be binary - clear or opaque?"... can we please STOP treating silver grains as BLACK HOLES? One of the reasons there are layers in film is to add dynamic range... for example, to extend Dmax by stacking grains because just one grain, fully developed, on a Z-axis doesn't BLOCK ALL INCOMING LIGHT. Even a macroscopic cluster of developed grains may not block all incoming light. That's why we stack layers! This argument of 'fully opaque' or not seems so damn obtuse to me. Let's just say the silver is as black as it can get, the filamentous growths are as black as they can get (doesn't mean they're black holes), and the size and density of these filamentous growths determine overall tone when viewed at lower magnifications.

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Furthermore, Vijay, let's <b>stop</b> talking about single grains being binary or not. It doesn't matter what the grain is when the AgBr is washed away... what matters is the density of filamentous growths from sensitivity centers. Why are you still talking about the tone of a grain? Eventually, unexposed subgranular spaces become just as clear as the gelatin (I believe), so it's the filamentous growths vs. clear film base. <b>So at this point let's just stop talking about the grains!</b>

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Anyone who sees an objection to my reasoning above, though, please do speak up :)

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Rishi

[rishij]

Oh, and Rich Evans? Holy crap, you da man!

 

:)

 

Rishi

[rishij]

Vijay: <i>"4. In the SEM images, especially in the 102x one, it appears like there is a cavity surrounding the silver, almost as if a silver halide crystal was present that is now gone, but has left that silver deposit behind. Is this a correct interpretation, or is it just random gelatin goo?"</i>

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Good work, Vijay, for pointing that out. Goes along with my whole idea I've been touting that <i>post-development</i> let's <b>stop</b> talking about grains and <b>start</b> talking about filamentous growths about a sensitivity center. I believe that the white cluster (of high atomic density) that is in the SEM images is exactly that: the filamentous growth about a sensitivity center. The low atomic weight (darker) stuff around it is gelatin, which passes light. So, yes, you can have subgranular structures in the end, but how much light they let through is only dependent upon their size, and how many of these are filamentous growths are clustered near one another. In the 102x magnification, we see two such clusters, separated by either gelatin or by clear film base where initially there was a grain holding AgBr. Who cares? It's clear now.

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So once again I ask, 'who cares about how many tones a <i>grain</i> can represent?' The more relevant question is 'how many tones can an area the <i>size</i> of a grain represent'? Probably not that many. An area the size of 500 grains, with three layers to add dynamic range? Probably thousands of tones (no, don't just multiply 500 x 3 layers and say: 1500 tones; there should be more than that, because the filamentous growths can be <b>smaller</b> than the grains themselves; i.e. subgranular in size, and so the real binary imaging element here is actually subgranular in size!).

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It's all starting to make even more sense now :) Beautiful. What teamwork. Including he who consistently played devil's advocate, Vijay :P

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Rishi

[rishij]

Vijay: <i>"You changed the definition of grain on me there didn't you?"</i>.

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Daniel: <i>"A single deposit of silver left over from the development of a single silver halide crystal."</i>

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Just so we're clear, then, Daniel's definition of post-development 'grain' is what I call 'a filamentous growth

from one (or more than one very close-by) sensitivity center(s)'.

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Yes?

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As I understand it, there is no silver halide <i>crystal</i> left after all AgBr is dissolved away during

development!

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Rishi