Around how many silver halide crystals are typically in a single B&W 35mm frame ??

Google search results brings up very different figures. One source said 100 million and another source said 84 billion. Kodak themselves say “billions of silver hailide crystals” which isn’t exactly very helpful.

Depends on how you define a 'crystal'. It also depends on the film and its physical structure, evidently . I think it's going to be hard to put a firm number onto this one.

If you assume that a single tabular grain is around 500nm in diameter and you put a single layer of them side by side with no spacing, you'd end up with around 48000 x 72000 = 3.5 billion grains. But they don't lie neatly side by side; there'll be some space between them, and on the other hand, they're not in a single layer either, but suspended in a relatively thick gelatin matrix. In any case, 100 million sounds way too far on the low side and the 84 billion sounds quite plausible, especially for a color film with its many layers. I'd guesstimate that a B&W film like TMAX100 would be somewhere in between at maybe a couple dozen billion halide crystals. That's a pretty wild guess, though.

Viewed through the emulsion thickness, a median grain of developed APX would be something over 1 micron, but the crystals smaller ~0.2-2 micron.

Define "typical film" first.

Depends on the film speed, among other factors.

Lucamancini said:

Google search results brings up very different figures. One source said 100 million and another source said 84 billion. Kodak themselves say “billions of silver hailide crystals” which isn’t exactly very helpful.

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I think your question proves that you've left the realm of photography and need a reality check to get back to picture-making (been there myself).

RalphLambrecht said:

I think your question proves that you've left the realm of photography and need a reality check to get back to picture-making (been there myself).

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I wouldn't make assumptions. I don't know what prompted the OP to ask this question, but for me, thinking about this only inspires me more. You never know where the winding roads of curiosity may lead you

Daniela said:

I wouldn't make assumptions. I don't know what prompted the OP to ask this question, but for me, thinking about this only inspires me more. You never know where the winding roads of curiosity may lead you

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Well said, Daniela! I agree. And we really don't know the background to OP's question; for all I know, he might be looking for parallels between the grain in film and a human population so they can apply this thought to an art project.

Then again, it could be just an AI question designed to waste our time. I sure our future will be full of that -- if we let it.

How many angels...........

xkaes said:

it could be just an AI question designed to waste our time

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So far it's pretty much the other way around - people making up inane questions for AI and in the process waste kWh's with it.

I'm going to say 1 imperial pint.

RalphLambrecht said:

I think your question proves that you've left the realm of photography and need a reality check to get back to picture-making (been there myself).

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I’m with you on this one Ralph….

Daniela said:

I wouldn't make assumptions. I don't know what prompted the OP to ask this question, but for me, thinking about this only inspires me more. You never know where the winding roads of curiosity may lead you

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Oh, Ido know; down another rabbit hole sway from creativity into the fascinating realm of photographic engineering and science!

I'm still counting. Be back soon.

Don't hurry on our account.