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High CRI LEDs?

Blarg King

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Hey all, I want to build an LED light panel for photo/video work. The thing is, I don't want to use cheap white LEDs off ebay because the light quality is likely garbage.

I've been trying to find a source for some 5mm/10mm LEDs with decent color rendering. Ideally a neutral white between 4000-5000 K. I've not had to look for something like this before and Im having no luck. Im not even entirely sure what Im looking for exists :/

Anyways Im turning to here because Im sure a lot of you have more experience getting hold of unique/uncommon lights, and if any of you can point me in the right direction it would help me out quite a bit.

Thanks!
 



Cyparagon

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Don't use 5mm LEDs (for anything besides indicators). The light output is low, the heat dissipation is poor, and this isn't 2005. Add CRI 90 to your search terms.
 

Benm

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I'd skip on the standard 5mm packaged led's too for this.

You could find some decent leds with good color rendering in either the 1 to 3 watt star packages, as well as in 5050/5630/2835 smd packages. Often the 'standard' white ones have pretty horrible CRI though, so look for this specification in any seller listings.

They are usually advertised as 'CRI 90+' or something similar on ebay etc. How accurate that really is remains to be seen though.

If you stictly need a big area source with good color rendering you could also consider TL. Those come with very good color rendition (for example from philips with CRI of well over 90), are quite efficient at full brightness, but not very dimable.
 

Blarg King

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Okay no capsule LEDs. I tried searching "90 cri LED" on ebay and its mostly either lightbulbs or LED strip. I suppose LED strip could work. I had some small white SMD strip for my PC case and that stuff was hella bright.

How is heat dissipation for smd strip? If I adhere it to say a thin aluminum backplate would that be enough to keep them cool do you think?
 

Benm

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TL as in tube light, fluorescent lamps as you may call them depending on where you are from.

LED strips can work very well if you want to build a light panel. You can just stick several rows of strip side by side to get a sqaure/rectangular area lit.

For most LED strips cooling isn't a huge problem: they are often something like 60 leds per meter, with ~0.5 watts for each led maximum. Many come with an adhesive tape back so you can stick them on a metal housing and that's usually enough heatsinking.

Heatsinking varies with how densly you pack them really. Roughly you could say that:

10 watts/m2, no problem at all
100 watts/m2 will get warm, some airflow is required
1000 watts/m2 will probably overheat without additional heatsinking and/or strong airflow.

You'll probably end up around that 100W/m2 figure - at which point you'd want the backplate to have at least free air circulation around it, so don't box that in completely.
 

Blarg King

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TL as in tube light, fluorescent lamps as you may call them depending on where you are from.
Ah. No that wouldn't work too well. I want it to be portable and able to run off a battery for a decent amount of time. Fluorescent tubes would be too fragile and more complex to work with, not to mention bulkier.
 
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will manners

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Add CRI 90 to your search terms.
Seriously that's all the advice you'll need for what you're looking for.

Forget about the LED strips that you use in your PC case. You won't find a high CRI equivalent for a reasonable price.

What's your budget?
 

steve001

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Hey all, I want to build an LED light panel for photo/video work. The thing is, I don't want to use cheap white LEDs off ebay because the light quality is likely garbage.

I've been trying to find a source for some 5mm/10mm LEDs with decent color rendering. Ideally a neutral white between 4000-5000 K. I've not had to look for something like this before and Im having no luck. Im not even entirely sure what Im looking for exists :/

Anyways Im turning to here because Im sure a lot of you have more experience getting hold of unique/uncommon lights, and if any of you can point me in the right direction it would help me out quite a bit.

Thanks!
Have you ever visited Candle power forums? If anyone knows it's these folks. The right word search brought up this site. https://www.flexfireleds.com/high-cri-93-series-ultrabright-led-strip-light-by-the-foot-natural-white/
 

Benm

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If the spectrum graph is real that would make a good candidate indeed.

These strips are convenient to use in a light box since they can usually be cut at every 3rd led and then connected to another piece easily completing an evenly lit rectangular area.

One thing i cannot tell from the listing is if these have adhesive tape pre-installed, which would be very convenient for a project like this.

If they don't have the peel back adhesive tape you can glue them down onto a plate yourself, but you probably should not use superglue or that as the solvents in that can actually degrade solder mask coating, risking the strips to randomly short out with the metal plate.

Glueing them down with some expoxy like glue will be fine though, and perhaps even the adhesive sprays would be enough to secure them in place.
 

Blarg King

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Alrighty. Anyone have any good ideas for powering these and having adjustable brightness?
 

Benm

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Normally you would use PWM to dim these things, but that can cause flicker/banding/beading problems with video and odd exposure problems with photography (with shutter times under 1/100 or so).

I'd suggest using a linear current driver for that reason. They may produce a bit more heat and loss, but the light is constant, so what you meter exoosure on is what you actually will get when taking the shot since the light output is constant.
 

Blarg King

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Hmm isn't there some way I can just adjust the current to the LED's to dim them without using PWM?
 




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