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Topic: Photographic flash  (Read 8096 times)

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Halma

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Photographic flash
« on: December 29, 2005, 01:38:47 PM »

I hope this isn't too off-topic here, mods+admins feel free to remove it if it is.

I was thinking about making my own chemical photographic flashes..

I've read about "flash" powder, but as well as being dangerous, it also produces a very loud sound when confined, and I'm not interested in bangs!

So how else could I do it?  I thought about magnesium, but magnesium strips burn too slowly.. Would it burn faster in pure oxygen?  What about aluminum, or iron?  Would aluminum foil burn in a high-oxygen environment?  Say, if I put some aluminum foil or steel wool in a container of (possibly slightly compressed) oxygen, would they burn fast enough to make a flash?

Offline Alberto_Kravina

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Re:Photographic flash
« Reply #1 on: December 29, 2005, 02:28:08 PM »
magnesium in oxygen is a good idea. Another possibility would be to burn titanium, I think.... :P

Offline constant thinker

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Re:Photographic flash
« Reply #2 on: December 29, 2005, 02:46:44 PM »
Grinding the magnesium into a fine powder (and aluminum would work probably also) should allow it burn faster. There would be more surface area. The first photographers used magnesium powder. I'd try out powdered aluminum or iron. Remember though safety first. ;)

http://en.wikipedia.org/wiki/Flash_photography
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Offline Bakegaku

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Re:Photographic flash
« Reply #3 on: December 29, 2005, 03:21:59 PM »
I think old fashion one-time-use bulbs used a very thin and long magnesium filament that coiled inside the bulb.  A strong electric current would be sent through it and the magnesium would burn off.
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Re:Photographic flash
« Reply #4 on: December 29, 2005, 03:39:26 PM »
I think old fashion one-time-use bulbs used a very thin and long magnesium filament that coiled inside the bulb.  A strong electric current would be sent through it and the magnesium would burn off.

Yup.  They were sealed inside the bulb in a pure oxygen environment so the slightest charge would cause it to instantly ignite.
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Re:Photographic flash
« Reply #5 on: December 29, 2005, 04:39:58 PM »
Used them back in seventies :)

Glass bulb was covered with some plastic so that they were not able to explode, as glass was always crushed by heat. They had blue dot inside - as long as it was blue, they were OK, once the dot changed to pink bulb was destroyed (I wonder what it was - cobalt salt? Checking if the gas inside is dry?)

Finally - not all cameras were able to use them. Electronic flash gives much more energy much faster, while magnesium filament needed some time to start burning and to reach maximum power. Thus cameras had two modes of flash synchronisation, one for electronic flash, one for magnesium bulbs.
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Halma

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Re:Photographic flash
« Reply #6 on: December 29, 2005, 10:56:37 PM »
Hey, thanks for the replies!

I don't imagine powder would work very well; I don't think it could be easily set up so that all the particles have access to oxygen.

A magnesium filament would be awesome, but where on earth can I get that?

Would copper work?  Thin copper wire is plentiful, but would it burn?  Would it burn green?

Offline billnotgatez

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Re:Photographic flash
« Reply #7 on: December 30, 2005, 04:48:03 AM »
One wonders if making your own photo flash would be more expensive than buying a system. Surely, over the long haul using a chemical that is burned would cost more.

In any case I doubt that copper would produce a quick bright white flash.

I remember once having a Xenon discharge tube having a bright white flash when the large capacitor released its charge.


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Re:Photographic flash
« Reply #8 on: December 30, 2005, 05:40:47 AM »
Note also that every flash has its color - which have to be taken into account when taking color pictures. All high end digital cameras allow to set a white point - that's a way of offseting ambient light and flash light color.

Magnesium flame is just white (well, in fact it is not, as it depends on the burning temperature), but other chemical lights may be colored and thus very diifcult to use.
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