Smoke and Mirrors
As linked from BoingBoing, here's a page from a photography blog which talks about a photographer who makes uncommonly lovely pictures of smoke, as you can see above.
Here's a paragraph from the Photocritic piece:
With the smaller aperture needed to capture the plumes of smoke properly, you obviously lose quite a bit of light. This is a problem, because in order to freeze the motion of the constantly-moving smoke, you need quite a fast shutter time. In practical terms, this means 1/250 or faster. Simultaneously, you can’t reduce the ISO value on your camera either, because the purile plumes of smokes would be ruined by significant amounts of noise. Needless to say, a coinciding need of low ISO, small apertures and high apertures means that you need a vast amount of light.
I don't know what an ISO value is*, but I do know this: "purile" isn't an English word, so I have absolutely no idea what the author's talking about. Googling "purile" gives a depressing 63,000 hits, but that doesn't make it a word; it makes it a really common mistake. Any spell-checker will red-flag "purile" and lead the conscientious writer to a dictionary, where the mistake can be discovered.
"Puerile", on the other hand, is a word, and if that's what's meant, then it's used incorrectly. I just don't know what's going on that sentence. Not a clue. I've written about "puerile" before: it means "childish", from the Latin. So obviously this isn't what the author meant to say: "childish plumes of smoke". "Pure" isn't what's meant, either, I'm sure; it doesn't make any sense in context. ("Pure", since you must be wondering, is from the Latin "purus". Same meaning.)
The context suggests something like "delicate" or "ethereal". So why didn't the author say that?
Naturally, the word "smoke" made me think of the phrase "smoke and mirrors", and I realized that I had no idea where the word "mirror" comes from, except to note that it suggests "miraculous". Will you be as delighted and amazed as I was to learn that they're essentially the same word?
The entire etymology, from Answers.com:
Middle English mirour, from Old French mireor, from mirer, to look at, from Latin mīrārī, to wonder at, from mīrus, wonderful.
"Wonderful" is exactly the word I had in mind.
*Well, I didn't before I started writing this, anyway. Then I looked it up. I still don't know precisely what an ISO value is, but at least I know that "ISO values tell you how fast your camera reacts to light", and "The lowest ISO value gives images with the least noise", which is a start.