How many grains in 35mm emulsion, difference per brand , effectiveness of recording
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 ?
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:
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
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.
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?
That document actually taught me a lot of new things, good thing i stumbed in here.
Originally Posted by Diapositivo
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This is an internet legend.
Originally Posted by Diapositivo
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 µm 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?
Last edited by hrst; 05-16-2012 at 12:01 AM. Click to view previous post history.
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!)
Last edited by Ray Rogers; 05-16-2012 at 02:11 AM. Click to view previous post history.
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.
PS I see Ray says it better and more concisely, in fact.
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.
Last edited by hrst; 05-16-2012 at 03:07 PM. Click to view previous post history.
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.