LED help

[rtv]

I'm in the TV biz..(and an led nut) anyway..i'm trying to make a camera light to replace the halogens we have used forever. i'm kind of leaning towards the mr16 5w or 7w. In my searching i can only find these in other countries
china austrailia Uk poland etc etc none in the USA!! anyone know of a good supplier in the USA? Ive found the leds themselves but not in the MR16s with
internal drivers.

Thanks for your help,
rtv

 

[laserblue]

how much is the price of those LEDS?

 

[rtv]

about $40

 

[SemiMan]

Well generally the reason why they have not been out is the potential performance has been too low with available LEDS. The claims for the MR16 replacements are often well beyond what they actually do. I would look for some to come on the market shortly based on Cree, Lumileds and OSRAM LEDS with the potential to be in the 500+ lumen range or similar to 35W and up Halogens. That said, watch out for the spectrum. Your camera may not color balance that well to an LED based light.

Semiman

 

[rtv]

Thats a good point about the spectrum and color balance...i guess i'll just have to "try and see"

Thanks
rtv
ps I'm looking at the osram ostars now....1000 lm!!

 

[PhotonWrangler]

The ostar looks interesting. It wouldn't be hard to power it from a 12v brick.

 

[rtv]

not so sure about that...they want 24v!! maybe a DC to DC converter would work. i sure DON"T want to use 2 bricks!!

rtv

 

[PhotonWrangler]

Oops! Missed that. Yeah, two bricks would be a bit much.

I ran across a high wattage multi-chip LED from DigiKey recently. I think it uses a series-parallel setup so it runs around 10 volts. If I can find the specs and part number I'll post it here.

**Edit** Just found a Lamina array at DigiKey, 10.8v at 5a and over 1800 lumens at 3900k. It's a little pricey at $130, but it's a quick way to get an LED array that's close to halogen color temp and compatible with a brick. This could be a sweet camera-mounted light.

 

[rtv]

very cool...i'll investigate.. although it seems expensive for an led, compared to what i have to pay for other lights it's cheap!

Thanks!!!

wow! they really have their color temps mixed up on the pdf

 

[VidPro]

i made a video light with these "blue" white leds and the colors were terrible, then i started making combos, adding in bits of green (just a tiny bit of green) and red, lots a red, and finnaly got a usable 20W led light that worked better than the 50W incan.
it had
3 high powered white leds
a amber high powered led added selectivly for incadescent
both using optics at about 10*
many 8* Red 5mm leds for blending into the main
many 20* 5mm white leds for blending
many 10* amber leds for blending
a few 20* green leds for blending
4 knobs and 3 switches to controll it all

then a drop down difuser because of the mess of partly blended colors, and finnaly it worked.

then i got into the usual 8+ types of light in the field, white balance the camera TO the field light, then readjust the led light to match it. 2 second later my subjects were next to a window, readjust everything again.
then under Mercury vapor, 4 colors of florescent, sodium vapor, 3 yellows of incan (from low power bulbs to high) , and 3 colors of outdoor light, sunset sunrise and everything else. it could adjust to any of them , given enough time.
finnaly i went insane, and told people that the color was a film effect, and they should pay more for it

sooo, if you get some "white" leds, toss at least a red in there, like the "pink panther" light , without it you will have ugly light.
another design i was looking at (long ago) was luxeon rings, because they interlocked, a 10ring of "white" a 6 ring of amber, and then stuff a red in the center, $1300 of just leds :-(

the ultimate would be something with RGB full blended (hard to do) with 12 instant microcontroller settings, for light matching.
i know how to get RGB blended now, but not blended AND thrown a distance, only enough for a floody light.

i use a 100W PWM incan now, because nobody else (assistant) could even operate the other one.
and a bunch of other stuff, but as for the on cam light, i am waiting for magic tri-color phosphors to be on leds, like on full spectrum florescent.

they are comming out with a new "warm" led that starts with a different blue die underneath, took them long enough, with it warm leds will be more efficient, but there will still be a big gaping hole in the spectrum.

 

[SemiMan]

You may find that an RGB array gives an even poorer result when taking video than a white LED. The narrow spectrum of the leds reflecting off what you are trying to video gives some unexpected results. The wide spectrum of a standard white LED will be much better in most cases and certainly more repeatable.

You may be best off to start with neutral white and add in some yellow.

You can go colored LEDS, but then you really need to consider at a minimum red, blue, green and amber and even then you likely may want to add in some cyan. This is the only way you will get proper reflectance off objects. While you can create any perceivable color with RGB when the eye is looking at the source, it is a completely different ball game when it reflects off an object.

Reading your post and I see you are in the TV business. That likely means you are working with some high end cameras. I will assume then that you can tightly control the individual channels for white balance on your camera? I would create either a Cool White + Amber or Neutral White + Amber and then work on the color balancing. You will have to be careful though, the Amber changes a lot with temperature. In practice, you may be better off just sticking with a good neutral white (which has more red output than cool whites) and then work on the color balance with your camera. Just make sure you save it!

Semiman

 

[VidPro]

the pro cameras have 3 seperated chips, like the 3 channels in photoshop,takes a red green and blue collection, then process that.
so its like trying to get a signal to all 3 , which reduces grainey noise, as can also been seen in photoshop. it uses filters that only send one color (range) to each B&W chip collector thing.
i think there have been 4 filtered collection too, but its not as common.

if you can get all 3 chips out of "gain" (grainey) so to speak, by having something anything going to all 3 you reduce the noise, then "balancing" is done AFTER that color light collection happens in the front, the toning down of one or the other in the "processing" in the hardware after the chips collect.

so i donno how the Short spectrum in the seperated colors would effect that exactally.

plus the WAY they assemble a RGB for high lumens, might not be the way you would assemble it for "filtered light chip collection".
for example if you lean the reds into orange red, you get more visual output (cute specs) , but less actual red. then they have some RGBY which fills the green and red up (there is no yellow collection chip) , but if you look at a seperation in photoshop, the blue is grainey when shot under low incadescent light, the red is grainey under white led spectrums. the green is rarely/never grainey, as lots of all the light types have sufficient green chip triggering.

i really dont know, because the cameras are also tuned to the "box" that we are usually stuck in anyways. but that is what i am seeking is something that takes all that into account, zooms from wide to tight, and it doesnt really exist.

and in Channels in photoshop, you CAN observe this stuff, with a digital still camera picture also, so to see it, you dont "have to" see a digital video frame, some of the same things occur with other electronic light collection methods too.