LED Light Panel Questions

sfoster · May 18, 2015

I was slow roasting everyone with my hot lights yesterday, they all got really tired a few hours before wrap time… I need some LEDs or something that is low heat.

But it's kind of confusing, look at this one
$240 for 900 lumens
$70 for 900 lumens

Why is there such a huge discrepancy .. just because one is marketed toward people making films? :weird:

I think the second one needs a little bit of wiring work to make it a standard plug.

Also this whole "wattage equivalent" they all list.. it seems to vary wildly and have little correlation with the actual wattage the light takes.

Any thoughts or input on LED lighting ?

sfoster · May 18, 2015

I'm strongly considering buying a power strip, adaptors for light sockets and then plugging in a row of 4 led spotlights.. would cost about $100 and be a 500W equivalent.

sfoster · May 19, 2015

I guess I should've posted in this in the cinematography and lighting section. Okay here is an update.

I ordered a 120W LED worklight, and I'm going to build my own from a power strip too.
I'll do tests and post results next week.

Morris · May 19, 2015

Some of the cheaper LEDs have a tendency of giving a greenish tinge.

sfoster · May 19, 2015

Morris said:
Some of the cheaper LEDs have a tendency of giving a greenish tinge.

It's better than slow roasting my actors. Everyone shut down 2 hours early.
The DIY one I am making will use nice bulbs..

Thanks for telling me - I'll make sure to include a custom white balance for each test. In addition to an AWB.

WalterB · May 19, 2015

The difference comes from differences in CRI values: C-something Retina Index which is a scale to indicate how close a light is to full spectrum daylight.
Cheaper LEDs are often (more) greenish, because the spectrum is weak(er) in the magenta area.
Above CRI 90 is considered high and they are more expensive.

And ofcourse, marketing plays it's part probably as well...

sfoster · May 19, 2015

WalterB said:
The difference comes from differences in CRI values: C-something Retina Index which is a scale to indicate how close a light is to full spectrum daylight.
Cheaper LEDs are often (more) greenish, because the spectrum is weak(er) in the magenta area.
Above CRI 90 is considered high and they are more expensive.

And ofcourse, marketing plays it's part probably as well...

I thought it was color rendering index but yeah i get what you're saying.

jax_rox · May 19, 2015

Morris said:
Some of the cheaper LEDs have a tendency of giving a greenish tinge.

All of the cheaper LEDs tend to be green. The only film LEDs I've encountered that don't look green at all on screen are in the thousands of dollars to buy.

WalterB said:
The difference comes from differences in CRI values: C-something Retina Index which is a scale to indicate how close a light is to full spectrum daylight.
Cheaper LEDs are often (more) greenish, because the spectrum is weak(er) in the magenta area.
Above CRI 90 is considered high and they are more expensive.

You mean Colour Rendering Index?

You'll struggle to find a cheap LED with High CRI.

WhiteOpus · May 20, 2015

So I would ask some of the more experienced people here, is the cost-cutting worth the compromise in image/color? This seems like an EXTREMELY cheap way to get a LOT of light, and if a slight green spike is the only issue, I'll grab a few from Amazon this afternoon.

sfoster · May 20, 2015

WhiteOpus said:
So I would ask some of the more experienced people here, is the cost-cutting worth the compromise in image/color? This seems like an EXTREMELY cheap way to get a LOT of light, and if a slight green spike is the only issue, I'll grab a few from Amazon this afternoon.

It also make me wonder if a slight magenta gel would correct the tinge.
I'm going out of town this weekend so I won't be able to do my tests until next week.

Power strips all have slots on the back for screw heads, so I can easily mount them to a 2x6 strip of wood.

Now I just need to find a cheap stand for a stick of wood + pivoting head.
Any suggestions?

WhiteOpus · May 20, 2015

here's my design
it's been a while since i went to school for engineering but i think this should work.

Sweetie · May 20, 2015

It also make me wonder if a slight magenta gel would correct the tinge.

It could in theory. In practice, I think you'd get yourself into more trouble than its worth by pushing it the other way.

The issue isn't exactly the green (while it is a problem), the problem with the lights having such a low CRI, each light may have a slightly different color. At the level that you're working, the benefit of having more light (even with a low CRI) will outweigh the downside of shooting without lights. In other words, if the option is no lights vs using these, use them.

You can get into trouble when color grading when you're using lights with different temperatures. Just be aware of it.

sfoster · May 21, 2015

Sweetie said:
It could in theory. In practice, I think you'd get yourself into more trouble than its worth by pushing it the other way.

The issue isn't exactly the green (while it is a problem), the problem with the lights having such a low CRI, each light may have a slightly different color. At the level that you're working, the benefit of having more light (even with a low CRI) will outweigh the downside of shooting without lights. In other words, if the option is no lights vs using these, use them.

You can get into trouble when color grading when you're using lights with different temperatures. Just be aware of it.

I am shit at color grading anyway, with a macbook and an uncalibrated monitor etc it's hopeless

Sweetie · May 21, 2015

Not everyone can do everything. You are allowed to have other people on your team /wink

WalterB · May 21, 2015

jax_rox said:
......
You mean Colour Rendering Index?
.....

sfoster said:
I thought it was color rendering index but yeah i get what you're saying.

My bad.
You are both right.
I mixed it up with another acronym Dedo (the CEO of Dedo Lights) uses to test lights as well, because in the CRI test skintones are almost completely ignored. At Dedo Light they measure it against another palette as well and it has retina in the name...

Oops.

BTW: if he is in town to do a presentation: go!

sfoster · May 27, 2015

I was told the LED work lights I ordered had a plug.. but they just came with two wires sticking out. Not even a grounding wire.

Going to take me some extra time.

Meanwhile for the home made ones.. I think I have to make my own soft box to fit but there must be some sort of adaptor I need to buy in order to mount a swivel head on top of a light stand? I found one for cameras but the bolt seems a little too short for something like this.

I haven't bought any stands just yet. Not sure what is out there.

sfoster · Jun 3, 2015

So those LED lights I ordered had a wrong description .. they don't even work with house power at all, they're DC!

no time to buy anything else, I'm filming tomorrow.
This is what I've built - 100W of daylight balanced LED

Going to paint the insides white tomorrow morning.