Halogen Spotlight for after sunset beach shots....

Thread view:

Enable EMail Alerts

Start New Thread

Thread rating:

Tom - 08 Mar 2006 06:59 GMT

So, I am interested in shooting the shadows on the sand...even when I
have run out of time and the sun has gone down. A Flash won't let me
pick out angles...but my new 12,000,000 candle rechargeable Halogen
Spotlight for 30$ will give me an hour or so of "light"!

Now, what to do about that flashlight style center bright spot? How do
I defuse it and still get nice sharp 'sunset style' shadows?

I'll be using a D50 18-55, until I start buying primes...
thanks - t.

Reply to this Message

zeitgeist - 08 Mar 2006 10:11 GMT

> So, I am interested in shooting the shadows on the sand...even when I
> have run out of time and the sun has gone down. A Flash won't let me
[quoted text clipped - 3 lines]
> Now, what to do about that flashlight style center bright spot? How do
> I defuse it and still get nice sharp 'sunset style' shadows?

get a video camera light.

try this, get one of those fresnel magnifying plastic sheets, used instead
of reading glasses, some are book sized. (but they might not be, uh, fire
proof.)
maybe the lens off an old spot light might work. find an old enlarger and
salvage the condenser lenses and see if they are any help.

why won't a flash let you pick out angles? Oh, cause its a flash, well use
your flashlight to find the angle and put your flash there.

Reply to this Message

mark.thomas.7@gmail.com - 08 Mar 2006 11:25 GMT

Sadly, I think you will find that once you diffuse those '12M candles',
they won't give you much light at all.. And to get an even spread I
doubt that a fres-lens will help - I would suggest maybe frames of
ripstop nylon, or drafting film, which will wipe so much light out....
Plus awkward, if not useless in windy conditions.

And lastly a $30 light may not like being operated continuously for
more than a few minutes.

Call me a pessimist, but I suggest you simply get up earlier in the
mornings... (O:

Reply to this Message

Andrew Haley - 08 Mar 2006 15:10 GMT

> Sadly, I think you will find that once you diffuse those '12M candles',
> they won't give you much light at all..

Well, let's see. A wax candle generates a nominal 12.5 lumens, and a
tungsten halogen bulb has a luminous efficacy of about 25 lumens/watt.
So, to match 12 million candles with tungsten you'd need

12*10^6 * (12.5/25)

About three megawatts, in other words. I wonder how big that
spotlight is...

Andrew.

Reply to this Message

Andrew Haley - 08 Mar 2006 17:39 GMT

>> Sadly, I think you will find that once you diffuse those '12M candles',
>> they won't give you much light at all..

> Well, let's see. A wax candle generates a nominal 12.5 lumens, and a
> tungsten halogen bulb has a luminous efficacy of about 25 lumens/watt.
> So, to match 12 million candles with tungsten you'd need

> 12*10^6 * (12.5/25)

> About three megawatts, in other words.

Duh. Six megawatts.

Andrew.

Reply to this Message

mark.thomas.7@gmail.com - 08 Mar 2006 20:21 GMT

I trust/hope you were being as sarcastic as I was. A 55w halogen
globe, which is what the OP has, I'll wager, actually gives somewhere
in the tens to hundreds of thousands (eg maybe 12,000 (not 12 million)
'candlepower'). There is *no* direct conversion from CP to watts -
el-cheapo lights take great liberties with their specs ("oh, that
reflector probably means we get a thousand times more light, so let's
call it 12,000,000").

So it's a 55 watts, or at best 100. Versus 6MW? That one would need
quite a power supply...

And even the smallest continuous halogen light for photographic use is
probably a 250W at least. I wouldn't bother trying to diffuse anything
less than that...

(O:

Reply to this Message

Tom - 09 Mar 2006 01:03 GMT

>I trust/hope you were being as sarcastic as I was. A 55w halogen
>globe, which is what the OP has, I'll wager, actually gives somewhere
[quoted text clipped - 13 lines]
>(O:
>

Yes to the realistic assessment of actual light output...its driven by a
12v 7hr battery, and I suspect I can get at most 2 hours out of it...so,
3ah X 12v = 36watts?...maybe 50w, but I can't see 100w. I don't want to
pull the bulb, might break it, so, lets say 50 watts and a 6" reflector.

What would be the pro or pro-sumer/ebay choice for an hour of portable
lighting useful for taking stills, with or without a tripod, through a
D50 18-55 3.5 and slower, and, low noise (iso closer to 200 then 1600),
as I would like to blow up the good ones.

If the "right choice" is, oh 10x in cost over my $30 spend, I'll keep
what I have and report back in a week or two after the sand thaws out.
On the other hand, if I can buy something made for the job used for <
$100, well..then I won't have to upgrade later :-)

- thanks, Tom

Reply to this Message

Jeremy Nixon - 09 Mar 2006 05:57 GMT

> What would be the pro or pro-sumer/ebay choice for an hour of portable
> lighting useful for taking stills, with or without a tripod, through a
> D50 18-55 3.5 and slower, and, low noise (iso closer to 200 then 1600),
> as I would like to blow up the good ones.

Strobes powered by battery packs.

> If the "right choice" is, oh 10x in cost over my $30 spend,

No, you're still in the wrong order of magnitude on that. It would be
thousands, and probably not just one or two.

Signature

Jeremy | jeremy@exit109.com

Reply to this Message

werdan - 09 Mar 2006 05:04 GMT

>> Sadly, I think you will find that once you diffuse those '12M candles',
>> they won't give you much light at all..
[quoted text clipped - 9 lines]
>
> Andrew.

Candlepowper is a bit like PMPO ratings for speakers. Great for advertising, useless for practical
measurements which you've just demonstrated.

Assuming that it's powered by a Sealed Lead Acid battery, the heaviest that you want to carry would
be about 7.5AH 12v.
Lets be really generous and multiply that by 4 to give 30AH.
P = V * I so 3000000 / 12 = 250000 Amps.
30AH / 250000A = 0.432seconds.

I would try to keep the shutter speed faster than 1/4 of a sec ;-)

Reply to this Message

mark.thomas.7@gmail.com - 09 Mar 2006 10:25 GMT

> P = V * I so 3000000 / 12 = 250000 Amps.

250,000 Amps, hey...? I'd suggest you would probably want something
fairly solid in the way of wiring for that setup, and stand back when
you flick the switch.. wooohooo! (O:

A video light is probably the best solution you've been offered. Or
the other one, to use a flashlight to get the direction, and then use
flash.

But a lot depends on what sort of area you need to evenly illuminate..?

Reply to this Message

Tom - 09 Mar 2006 14:28 GMT

...continued fun with math and exploding wires..snipped...

>A video light is probably the best solution you've been offered. Or
>the other one, to use a flashlight to get the direction, and then use
>flash.
>

Yes, a single consumer video light seems to be available in the
$100-$300 range (with batteries)..

>But a lot depends on what sort of area you need to evenly illuminate..?
>

Great question. the key area will likely be about 10'x10'...but I don't
really want that to appear to be in a cave. Hmmm...I know I won't
buy/carry enough light to shoot in the dark - I would just like enough
supplemental lighting to get interesting shadows and depth effects when
the natural lighting is too diffuse (clouds or sun just set).

Reply to this Message