Filter correction advice needed....

[Mike Harrington]

I bought some cheap LED lights....
as expected they are not quite the best color wise...but i still want to salvage them to use at times as they are freaking bright

compared to my kinos they come across about 1200k degrees to hot (6700 ish) and they need about 3/8- 1/2 minus green (i used 3x 1/8 minus greens rosco stacked to get the tint during auto white balance to match the kinos)

the minus green also brought the color temp down to about 6500....

I am not sure on the color science.....but there must be a single filter that would give me close to what I want....
basically combining the 1/2 - green with something CTO that can bring the temp down 1000k or so....

any body have any insight into this....i guess i could always stack filters....just hoping there could be 1 single one that could do it...

and yes...this is a bit of a hack...I know...its embarrassing to even ask this question among a group of high end users...but I still want to use these on occasion (probably never as a key)

thanks

 

[Matthew Scott]

You shouldn't be embarrassed asking a legitimate question like this. I actually have the same color shifts with my LED's, but thankfully I have a dial on the back of mine that allow me to control the kelvin. Like you said, they're about 1000k out from the Kinos....Sorry I can't help with the Gel suggestion.....but there must be something out there!

 

[Phil Holland]

This is one of the major downsides to some of the cheaper LEDs panels out there. They drift green, some way green. There likely is one filter out there that will get you to where you want to go, but due to the variety of kelvin ranges and inconsistencies sometimes across the same manufacturers panels there probably isn't a perfect answer. To compound issues, during the course of some LED fixture's lifespan the color drifts further green. I've also seen panels drift faster towards green if exposed to heat, like leaving them in a hot vehicle.

What I would do in your situation though is pickup a Rosco sample pack. You might get one for free, you might have to pay a few bucks for them. Sift through those and find your appropriate strength minus green filter in there.

I ended up getting a variety of gels for both correction and more stylized looks then cut them all to size to just drop into the LED. Nice and quick. I do find myself using them less these days though. Great if you need a compact kit, a splash of color, or need lights near talent.

Hope that helps.

 

[Bob Gundu]

Here is an interesting read from Guy Holt on the spectral deficiencies of LED.

http://www.dvinfo.net/forum/photon-...spectrum-nowhere-near-flat-2.html#post1667436

 

[Mike Harrington]

ya thanks for the advice guys....

I guess what I was hoping for is some kinda online calculator...to combine filters and come up with a result...not sure if that exists...
i think i will grab a rosco sample pack do it the old fashioned way and stack some filters

in theory though...if one knew the color science...they should be able to run the numbers and come up with an ideal correction filter....that may or may not exist

 

[David Mullen ASC]

You're not going to gain anything in terms of stop loss with a combo gel, it would be the same as two gels put together.

If there were only one type of LED and it only needed to be corrected in one direction (like to 3200K with no green), then you could design one gel to correct it -- but there are many types of LED's and fluorescent fixtures with various amounts of green and with different color temperatures, so there isn't going to be one gel that works in all situations.

Back in the 1970's when most fluorescents were a common type of Cool White or Warm White, and were being photographed onto Kodak 3200K-balanced film stock, then there were "fluoro" gels and filters to correct them, but today's fixtures aren't as green and vary more in color temp... and often have to be matched to something other than 3200K, to various cameras that vary in terms of how sensitive they are to the green spike. And some of these lights vary in terms of the green spike depending on how warm they get.

 

[Phil Holland]

@David - Have you been able to shoot with the Nila LEDs yet? I've had about a breath of a second with them and thought the light was pretty good compared to damn near everything else I've used.

I'm somewhat on a mission to find low draw/high output daylight. Nila and Hive have been interesting to say the least.

 

[PatrickFaith]

I bought some cheap LED lights....
as expected they are not quite the best color wise...but i still want to salvage them to use at times as they are freaking bright
...

I am using real cheap LED's flood lights to shoot large rooms with hardly any power and heat ... but i'm mainly using the monochrome epic. This lighting approach drastically cuts costs in doing black and white shoots(i also am re-using my old lighting hardware to give more control to the led lights as in my inserted picture). Anyway, you can always use the LED's for bw or low saturation type shots. But i'm in your same boat with cheap LED's and color (i think it's even a bit worse then you state, as the emission bands of the led hit's the sensor's color filters in a weird way - so it's basically impossible to get skin colors right even though the light doesn't look to bad to the naked eye).

 

[Matthew Scott]

If you can adjust the temp with a dial, the cheap ones are really fine....I get beautiful skin tones, beautiful results. So many people are freaking out about cheap LED's. The one's I'm using (no-name china ones) cost me under $400 from eBay.

 

[Marc Wielage]

I have color-corrected many scenes that were contaminated with mixed lighting or bad source lighting to the point where the white balance was all over the place. It can be done, but even when it's corrected, it never looks quite right (to my eye). But it at least can look much, much better in post, to the point where it's acceptable.

So the answer to me would be: hire a good colorist.

 

[Mike Harrington]

buy cheap lights and hire a good colorist....
or buy good lights and hire a cheap colorist
:cheers2: