Pls recommend LED that suit for Video Light Panel

cursor

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Jun 24, 2009
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Hi everyone,
I am new in the forum, in fact I came upon this site while searching for information on LEDs.
Anyway, I planned to DIY a small light Panel using LEDs for video taking in low light area or just dim it down to use as fill in lights.
In the process of search and trying the LEDs, I can't seem to find one with the correct colour temperature of around 5600K (daylight). Most LEDs that claim to be Daylight are all Cool daylight which already had a blueish tint. Look quite bad on video esp the skintone.
So I need some help here to suggest or narrow down the LEDs that I can try on.
My requirement:
1) To build a small panel of LEDs (5600K, High CRI) array (depend on the brightness of the LEDs, can mount 4 to 40.... as long as it can fit into a 10x10cm board.
2) Able to light up wall about 3x3m when the light is place 2m away from the wall. And able to thow the light far as far as 8m
3) Light intensity fall on the subject is adjustable, by a variable potential meter.
4) Simple circuit wiring if possible, like from battery connect to potential meter then parallel to all the LEDs. Hopefully no LEDs drivers needed.
5) Able to power by 4 x AA Rechargable (2600mAH) battery and can lasted for at least 3 hrs of usage.

So I need some expert input as in which LEDs should I choose and if this spec if even possible to meet in the first place.

Thanks in advance.
 

snarfer

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Feb 21, 2008
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Here is my analysis of your problem:

Assume Lithium batteries type 18650, 2600 mAH, 3.6v nominal

2600 mAH * 3.6 v * 4 batteries = 37.44 Watt Hours

37.44 Watt hours / 3 hours = 12.48 watts

High CRI LEDs average 60 lumens/ watt

60 lumens/watt * 12.48 watts = 1248 lumens

I know from experience that 1248 lumens will probably give you about 5-6 foot-candles at 2m, assuming no optics and lots of spread. Maybe it would actually be less.

Your video camera is rated at 320 ASA for a decent quality picture. Assume 360 degree shutter and 24 frames/second. So you have 1/24 second exposure.

Here is a chart from Panavision for showing required foot-candles assuming 1/50 second shutter.

Assume you're shooting wide open T 1.4. The chart says 8 foot-candles, divide by 2 because you have 1/24 second shutter instead of 1/50. So 4 foot-candles are required.

It looks like it could be possible. However you will definitely need a driver. Sorry I'm not sure where to recommend you obtain high CRI LEDs. The companies that make them usually don't distribute them at a retail level. Even some manufacturers of LED video lights don't use high CRI LEDs.
 

blasterman

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Jul 17, 2008
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Mouser.com sells the high CRI Seouls.

However, I would guess that neutral white 'quality' LEDs with a CRI of 80 or so *might* suffice for video work.

Combine cool white 5mm LEDs with low CRI to begin with and it does terrible things to flesh tones that is tough to balance out.
 

snarfer

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Feb 21, 2008
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Mouser.com is a good idea. I think the high CRI Seouls are only available in warm white though.

I just checked and found that Mouser is selling the new Sharp Zenigata High CRI LEDs. Part numberGW5BNC15L02 if that link doesn't work. Maybe 3 of them together would work for you.

If it was my light I would put them all in series and run them with a boost driver. But that's just the way I do things.
 

cursor

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Jun 24, 2009
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Mouser.com is a good idea. I think the high CRI Seouls are only available in warm white though.

I just checked and found that Mouser is selling the new Sharp Zenigata High CRI LEDs. Part numberGW5BNC15L02 if that link doesn't work. Maybe 3 of them together would work for you.

If it was my light I would put them all in series and run them with a boost driver. But that's just the way I do things.

This part is nice... but the operating voltage is 10.2V.... my 4 AAs will not be able to generate that kind of voltage without a boost circuit.... And even with a boost circuit, it will not last for more then 2 hrs, I think. If this part is pair with a 12V battery, then it would be perfect!
 

cursor

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Jun 24, 2009
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I always learn something new when doing this DIY project.
Before I begin, I only know there is White LEDs. Once started then I know there is Warm and Cool white.
After I use cool white, then I realise that it belong to higher Color Temperature hence got blue tints. Which now I know I should look for LEDs that in the 5500K range.
Only when I come into this forum, then I know about CRI....
This is getting more interesting every step I move on (or fall back)....
 

videoman

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Jul 26, 2009
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I don't think they will last 3 hours. 2600mah is the problem. If the leds can take in 7.2V instead, how about a Sony NPF-960 or 970 Li-ion battery. They are rated at 6000mah and are not bigger than 4AA stuck together.
I get mine from power101.com if they have any left. Also get the charger for it.
 

Linger

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Feb 17, 2009
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advertised capacity does not always reflect the actual performance the cell gives. To further complicate the matter, different usage (high short bursts vs low continuous discharge vs. ....) at different temperatures and the same cell will perform differently, thus producing a range of 'rated capacities.'
 

Stillphoto

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Welcome Cursor, I think you're one of many here going after the same sort of build. So far, I'm really just waiting on some high(er) cri daylight balanced leds.

Even Litepanel's 5mm leds have a little bit of shift in them...hence why their filter kits include a minus green filter, as that is the direction they always seem to go.

I'm still weighing my options as far as batteries go. Might go after something exotic, who knows.
 

Archie Cruz

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Aug 1, 2007
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Welcome Cursor, I think you're one of many here going after the same sort of build. So far, I'm really just waiting on some high(er) cri daylight balanced leds.

Even Litepanel's 5mm leds have a little bit of shift in them...hence why their filter kits include a minus green filter, as that is the direction they always seem to go.

I'm still weighing my options as far as batteries go. Might go after something exotic, who knows.

I think the Lowel blender is based on my boss's white paper and will be a great product if they ever pay him his cut. Not shipping yet.
The short answer is that even if you can buy the right emitters, the rest of the build + time will cost you more than just buying it.
The subject apparently came up in CPF 5 years ago and was ignored. Now, too many big players already doing it. More will join in as LED's become the hot ticket in the years to come.
I personally like LED-Z & I also use Lupine Lighting ( bike lights) for on camera video. > http://www.gearninja.com
 

cursor

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Jun 24, 2009
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Welcome Cursor, I think you're one of many here going after the same sort of build. So far, I'm really just waiting on some high(er) cri daylight balanced leds.

Even Litepanel's 5mm leds have a little bit of shift in them...hence why their filter kits include a minus green filter, as that is the direction they always seem to go.

I'm still weighing my options as far as batteries go. Might go after something exotic, who knows.

Hi Stillphoto, for the warm welcome.
yup I am still searching around...
But likely to build the first prototype with Cree LED, XRE series if my memories never fail me.
But this LED will need a heat sink... also from the brightness, I think I will need only 3 or less to get the job done.
 
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