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View Full Version : How many grains in 35mm emulsion, difference per brand , effectiveness of recording



Mustafa Umut Sarac
05-15-2012, 05:17 PM
How many grains are there per 35mm BW and Color Film , How this number change per manufacturer , I want to compare Tri X and APX and what percentage of these grains are effective to record a picture ?

Umut

Diapositivo
05-15-2012, 06:25 PM
It's more "how much grain" than "how many grains", photographic grain is a non-numerable entity, like milk and butter. "Grain" is the visual perception of "clouds" of things that at the microscope look like more or less dense filaments.

Nice microscope pictures here:

http://cool.conservation-us.org/coolaic/sg/emg/library/pdf/vitale/2007-04-vitale-filmgrain_resolution.pdf

The numeric measure of grain is given either by resolution in line-pairs/millimetre, or by RMS granularity.

In the abovementioned document you'll find such measures for many films.

Hope it helps

Fabrizio

Mustafa Umut Sarac
05-15-2012, 07:43 PM
Thank you. Document is excellent. I loved the Kodak BW Film Comparison with violin pictures. Tri X and Plus X is giving very very noticable and natural texture. They are all different from others , not sterile.

John Austin
05-15-2012, 08:46 PM
Right, piece of film on the microscope stage, here we go

One, two, three, four, five, six, seven - Oooops, lost my place - One, two, three, four, five, six, seven, eight, nine, eleven, twelve, ten, thirteen . . .

What was that about a monkey, a typewriter and Shakespeare?

dehk
05-15-2012, 11:23 PM
It's more "how much grain" than "how many grains", photographic grain is a non-numerable entity, like milk and butter. "Grain" is the visual perception of "clouds" of things that at the microscope look like more or less dense filaments.

Nice microscope pictures here:

http://cool.conservation-us.org/coolaic/sg/emg/library/pdf/vitale/2007-04-vitale-filmgrain_resolution.pdf

The numeric measure of grain is given either by resolution in line-pairs/millimetre, or by RMS granularity.

In the abovementioned document you'll find such measures for many films.

Hope it helps

Fabrizio

That document actually taught me a lot of new things, good thing i stumbed in here.

hrst
05-16-2012, 12:50 AM
It's more "how much grain" than "how many grains", photographic grain is a non-numerable entity, like milk and butter. "Grain" is the visual perception of "clouds" of things that at the microscope look like more or less dense filaments.


This is an internet legend.

There actually ARE distinct grains (and those are called "grains"; "graininess" is the non-numberable entity resulting in from having grains); those work as the light-sensitive "sensors" in the film. There is a simple explanation; unlike pixels in a digital sensor, these grains exist in a very random three-dimensional matrix with a thickness comparable to 10-30 grains. Therefore, when you look at the finished product under a transmission microscope, you see a composite image of these grains overlapping. (In addition, most BW developers dissolve grains together and change their shape.)

The grains are just so small (in the range of 0.1 - 2 Ám or so!) that you need an electron microscope to see them clearly; so this is an another reason, normal visible light cannot render sharp images of grains and they are blurred. And, finally, you have to remove the grains from the thick emulsion for microscopy if you want to see them separately. See the attached image --- image courtesy Robert L. Shanebrook, Making Kodak Film, 2010 Recommended reading!

So, the original question is perfectly valid, and I can see it would be quite fun to talk about giga- or teragrains to a digital megapixel person ;). In larger formats than 135, I bet it would quickly become petagrains.

The number will be truly huge, because in film, a single grain works along with hundreds of others to form smooth gradation. (Although, contrary to an another internet legend, a single grain is NOT limited to on/off state but can develop partially. Still, the development is an amplification process with a factor in the range of 1000000, so that for a really smooth gradation, a high number of active development centers (or spots of latent image; a few Ag atoms) is needed, and this happens in multiple grains.)

What would be the way to count the number of grains? First approximate their size distribution (e.g. from electron micrograph), then create a simple mathematical model for their weight, and use some known amount of silver in the film?

Ray Rogers
05-16-2012, 02:48 AM
Hi HRST!

Nice summary!

I think you and Diapositivo are really saying the same thing.

Diapositivo calls silver halide crystals "things" rather than "grains",
but you both point out there are AgX crystals and that
there is a perception of a "non-numberable entity" resulting from observing en masse
what results from those crystals upon development (the filaments).

The same word "grain" is being used to describe 2 different things and
this continues to be a source of confusion;

I try to use the words like this:

"crystals" before development,
"filaments" after development and
"grain" or "graininess" for the visual impression one gets
when looking at massive numbers of filaments with the (naked) eye.

(Oh, and of course, the book by Sheppard!)

Diapositivo
05-16-2012, 03:07 AM
The "graininess" we observe, which is a visual perception thing, has not much to do with the grains at the microscope, which are not visible, or indirectly perceivable, by the human eye.

A pixel is perceivable as such and can be counted as they are ranged and don't overlap. The "grains" overlap and what we see is some form of a "cloud of edges of crystals" which we call grain because we see the "graininess" but not the crystals.

Although I appreciate the implied argument that there is more resolution in film than in common digital sensor :) (which I confirm with practising both technology and being able to confirm that in a 135 frame scanned by a film table scanner at 4000 ppi resolution there is WAY more detail than in my 11 MP serious digital) I think that calling crystals "grains" as if each of them was perceivable by the human eye (as it happens with pixels) is a bit forced, but would not like to descend into a nominalistic quarrel here.

Those crystals whose edges overlap form areas of higher or lesser density but one cannot "count" the crystals, or the grains, in the way one counts "pixel" to arrive at a resolution measure, the resolution measure being the reason of the original question.

Fabrizio

PS I see Ray says it better and more concisely, in fact.

hrst
05-16-2012, 03:50 PM
Well, if a pixel is visually perceivable by eye, then the system has failed miserably in its very basics. I'm not saying that doesn't happen. It's actually one of the facts that separate theoretical and realistic digital imaging; even today, digital displaying on screen has not made a single step in last 10 years and this is one of the big reasons why digital pictures look oversharp, lacking detail, and film scans look overgrainy and/or blurry when shown on computer screen. But in theory, the idea goes that the pixel size is decreased until it is invisible to eye as a single pixel. This idea is actually somewhat close to that of a single "grain" or "crystal" or whatever in film, except that more grains/crystals than one are needed to render tones. In both cases (digital/film), the system is (or "should be") designed so that eye does not have enough resolution to resolve single grains/pixels. In digital, this "blurring" or combination process happens in two dimension, in film, it happens in three dimensions, and the third dimension prevents even electron microscope from seeing individual grains/crystals. But even if you cannot see them, they are there, and they can be seen indirectly, and understanding them is crucial. Furthermore, understanding is so easy that I find there is no reason to "hide" the construction of grain under typical internet statements like "there are no individual grains". (This is not a quote from you; it just came to my mind. We should actively try to smash internet legends every time we have a possibility to! :).)

I agree that the naming conventions are very confusing and "grain" indeed can mean both things, but I did't like the fact that you first presented as if the OP had something wrong while he didn't, but was just using one of the usual naming conventions you just didn't happen to like. Distinct crystals/grains exist and you could have just said that, accompanied with an addition that they are not necessarily called grains.

After all, understanding that the individual grains/crystals exist, and their shape, is a prerequisite to further understand how their composites look like; how the individual grain size is related to RMS granularity (the first causes the second, with other factors too of course); and especially, as we are discussing emulsion making, we are making those individual crystals. On this subforum, crystal size and shape play a HUGE role --- we would use the RMS granularity for the opposite direction, trying to deduce the average crystal size based on that.

On the terminology side, calling them crystals should be quite safe and misconception-free. I'll try to use that word from now on, and "graininess" for the overall composite effect. This way, the ambiguous word "grain" can be avoided completely.

As a bottom line, getting information available and elaborating on the world behind the basics is more important than what terminology we use. And, luckily, this disagreement in terminology has been good for that purpose.

hrst
05-16-2012, 04:11 PM
I have to further add that the OP's question also included:

"what percentage of these grains are effective to record a picture"

This would make absolutely no sense if "grain" were to mean composite effect of graininess when looking at the final image. So it's absolutely clear from the context that these grains are crystals in OP's terminology of choice.

Also, the plural form gives away the meaning.

As for the percentage, I think it's quite near to 100% for today's films. Of course, if you don't use the complete exposure latitude of the film, some of the smallest are not "used", but they COULD be used given enough exposure.

Diapositivo
05-16-2012, 04:28 PM
It's the idea of "counting" grains which I was objecting to, as they overlap both on the horizontal plane and on the "depth" of the film and so what we see is not a "number" of grains composing an image (like in a mosaic, or in a pointilliste painting, or in a digital picture) but the overlapping of borders of these grains, which makes the "count" of them misleading.

This very moment my screen shows me characters which are 1 pixel wide. I can clearly see, in text, the width of the pixels. They are "ordered" in a matrix and so counting them makes sense to asses the "resolution"* of the screen.
The "resolution" of the digital image (or the mosaic, the TV screen etc.) is strongly correlated to the number of pixels. Even if we don't perceive the single pixels (we certainly don't while looking at a move on the TV set) we perceive that the resolution depends on the "count" of the pixels. High definition TV gives perceivably a higher definition even if we cannot isolate the single pixels, we perceive there is a higher count of them forming the image, because the image is formed on one single plane of geometrically ordered tesserae.

This analogy doesn't stand well with "grains" because they behave differently. In colour film the clouds of filaments are "transparent" and their overlapping gives various areas of colours where the variation in colour can be continuous at a certain magnifying scale (well shown in the Vitale document) so that one doesn't have a matrix of pixels with an abrupt variation of colour from an atomic information to the next, like in digital, or in a mosaic.

Digital and analogue are IMO a bit like mosaic and watercolour. In a mosaic we can count the number of tesserae but in a watercolour we cannot "count" an equivalent, that's what I meant. Probably somewhere at some microscopic scale we can find some solid "grains" on the paper but that is on a completely different scale, and visual effect, if compared to the mosaic.

With black and white probably the filaments are more "opaque" and, although the darker or lighter effect is always given by the overlapping of crystals edges in the "depth" of the film (in colour film a yellow "cloud" can partially overlap with a magenta cloud and partially overlap with another magenta cloud, how do we count them, in black and white we have a section where the "dirtier" the water the "darker" the image, so to speak, and we could theoretically count the single particles of dirt in suspension, each being, I guess, quasi non-transparent), one can say that the "working" is a bit more similar to the digital medium because there aren't, IIRC, the "half transparent" crystals which happen to be in colour film (the filaments forming the clouds).

Fabrizio

* OK "resolution" itself can have several meanings.
I don't think we disagree. It depends on which microscope scale we consider "meaningful" for the comparison with digital.

hrst
05-16-2012, 04:42 PM
Yes, I think we just read the OP's question in different light. I was getting it in the sense of a bit humorous or "child-like" search for trivia, such as "how many grains of sand in Sahara desert?" -- So it actually wouldn't make much sense but would count as a "fun fact". Especially, when said to a digital person counting his megapixels :).

Maris
05-16-2012, 05:27 PM
A possible complication lies in the fact that the graininess of the final picture, a positive, is actually a map of the spaces between the grains of the negative.

Many times when I have looked at a very dense part of a negative through a grain magnifier on the baseboard of an enlarger I've remarked on the smoothness of the view. It's mostly dark with bright points here and there but I know those few widely separated "stars" will deliver conspicuous pepper 'n salt grain in the highlights of my final photograph.