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Schlock Mercenary
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April 19th, 2007

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12:26 pm - New camera !
So ... quite a while ago, I posted about the trouble I was having in choosing a camera to replace my poor old Optio S (lost while getting off a BA flight at Gatwick). Not quite as long a while ago, I came to a decision[1] to get the Optio W20. Then I dithered a bit longer while trying to decide where to buy from, and then failed to buy it from purelygadgets.co.uk (bad online ordering system, and their support people couldn't help much either). Finally, I ordered from Pixmania and it arrived on Tuesday. It's shiny ! And has many neat features - interval timer, very close macro (see below), nifty highlighting of under/over-exposed areas, waterproof (essential for Scotland), and still quite compact. I also got a spare battery and a nice neoprene case (both from eBay; the case fits the camera snugly, and I've not seen anything quite like it in the shops - look for seller "atomichh" - based in Australia, ironically).
Of course, I'm still thinking of eBaying an Optio S sometime, for two reasons - one is that the W20 doesn't work with the IR remote control that I have, and the other is that I want a camera that I'll feel happy about hanging from a kite. Clearly not something I want to do with my shiny new one !

And here's a sample image - taken from about the minimum focal distance, approx 1cm :
Close-up photo of water from tap

[1] Astrology is almost entirely silly, but Libran indecisiveness ? Very, very real, at least for me :-)
Current Mood: cheerfulcheerful

(4 touches | En garde !)


[User Picture]
Date:April 19th, 2007 01:28 pm (UTC)
You seem to be nicely demonstrating the break-up of a liquid jet there.
[User Picture]
Date:April 19th, 2007 10:40 pm (UTC)
a liquid jet

... otherwise known as the kitchen tap :-)
I took a few more photos of it later, and it does some seriously weird stuff further down. I feel sorry for anyone who has to try to work with the maths of the stuff.

[User Picture]
Date:April 23rd, 2007 09:59 am (UTC)
Very nice, especially the third and the fourth.

A part of what you see is reasonably easily explained. It demonstrates what's technically called the Rayleigh "sausage" instability. Surface tension at the air-water surfaces "wants" to reduce the surface area of the water. And it turns out that for a given volume of liquid, arranging it as a cylinder (like the jets when they come out of your nozzle) yields a surface area which is larger than a cylinder with wiggles on it , so the water "chooses" to make itself a wiggly cylinder (peristaltic, like a row of sausages). From there it's just a matter of time until a few milliseconds later, the wiggles develop into drops.

What's fun here is that it looks like your tap has multiple small jets coming out of it, so you get lots of small drops. These drops look like they get bigger, until they bump into their neighbours. Then they merge with their neighbours, and get even bigger! And then (maybe) air drag affects outside drops differently than inside drops, and you get more collisions, the complicated picture you see at the bottom. The little satellite drops probably come out of the drop collision and merging events.

If I had more time, I'd point you to some photos showing that this really is rocket science. In the meantime, if you're interested, get your hands on a copy of the Album of Fluid Motion by Milton van Dyke. It has lots of pretty photos, which you might find inspiring.
(Deleted comment)
[User Picture]
Date:April 19th, 2007 10:43 pm (UTC)
Thank you ! (and now there are more photos, in my other comment)

And the dragonfly is indeed one of mine - taken near Bothwell castle, which is near Glasgow. If I were organised and had tagged all of my LJ entries appropriately, I'd be able to point you to the entry where I wrote about visiting Bothwell, but ... well, I'm not. I'll let you know if I run across it, though :-)

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