A Good Size

On the phone with a gentleman who is hard of hearing:

Him: Do you have a 35-mm microfilm reader?

Me: I think so...

Him: Sorry, can't hear you. Do you have a 35-mm reader?

Me: YES, I THINK SO. IT'S THE STANDARD SIZE.

Him: And how big are the reels? 100 feet? 400?

Me: I HAVE NO IDEA. MAYBE IT SAYS ON THE MACHINE. I'LL GO LOOK.

Him: Okay.

I go look at the machine--no info at all. I grab a reel and bring it back to the desk, where I have to hunt around for a metric ruler.

Me: YES, IT IS 35MM.

Him: But how much film can you put on there?

Me: WELL, IT'S ABOUT 3.5 INCHES IN DIAMETER...

Him: (impressed) Oh, that's a pretty good size! You could probably put about 500 feet on there.

Me: OKAY, WELL, COME IN AND USE IT ANY TIME.

Him. All right, thank you very much.

I hang up

The Liberrian: Wow, for a minute I thought you were going to unspool the whole thing and measure how many feet long it was.

Me: NOT LIKELY.

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Later, The Liberrian [who majored in math] gets all dreamy-eyed, imagining the calculus problem you could do to find out how many feet of microfilm would fit on a reel, if you take into account the thickness of the film and the increasing spiral, etc. etc.

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Still later: OMG dude!
Someone asked this very same question on Ask Metafilter!
So I will definitely be figuring that out in my copious free time.
Yep.