Not All LED Panels Are Made Equal. Here’s How To Tell The Difference

Apr 30, 2015

Udi Tirosh

Udi Tirosh is an entrepreneur, photography inventor, journalist, educator, and writer based in Israel. With over 25 years of experience in the photo-video industry, Udi has built and sold several photography-related brands. Udi has a double degree in mass media communications and computer science.

Not All LED Panels Are Made Equal. Here’s How To Tell The Difference

Apr 30, 2015

Udi Tirosh

Udi Tirosh is an entrepreneur, photography inventor, journalist, educator, and writer based in Israel. With over 25 years of experience in the photo-video industry, Udi has built and sold several photography-related brands. Udi has a double degree in mass media communications and computer science.

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Today I want to talk about LEDs and CRI. You see not all LEDs were created equal. Most of the time when we talk about LEDs we talk brightness and color temperature, and that makes sense as those are easily measured and have great impact on our photos.

One thing that we often overlook is CRI. And what is CRI you ask? Well CRI stands for Color rendering index and it the number that has the bigger impact on the quality of light.

Let me explain.

You already know that not all whites are created equal. A florescent light is not the same as incandescent light, and those are not the same as an LED light.

Why CRI Matters?

Because white is actually made of combining all the colors in the spectrum.

The sun is a perfect example, if you put the sunlight through a prism (as Pink Floyd showed us with the awesome Dark Side of The Moon) you get all the colors of the rainbow.

This is not the case with all lights.

Some lights, like LED lights have more of one color and none of the other. The quality of the mix is measured with CRI.

We are going to use a handy device called a Spectrometer – the one that we are using for these test is called Lighting Passport from Allied Scientific Pro. It is a small boxy device that provides incredibly accurate results and we absolutely fell in love with it. We were also very surprised with some of the results.

CRI results

Let’s look at the sky. as we can see it has all color components in roughly similar quantities, with a slight shift to the blue as the skies are blue because of the scattering effect.

sky-spect

Now Let’s look at a cheap LED bulb. As we can see, there is a huge blue pike and a high green spike but almost no red.

led-bulb-spect

Another way to look at this is by using RA tests. RA tests test the how the light will render a certain color, with colors like red and green, but also colors like Caucasian and Asian skin tones.

Let’s compare the RA test results of the sun and our DIY built LED panel. Can you guess which is which?

sky-vs-bulb

As we can see R9 which is strong RED is absent completely from the cheap LED panel

Now, any CRI below 8o is not really suitable for photography and anything under 85 is quite marginal. Now for the full results

We tested several lights:

A cheap LED bulb from Dealextreme, A no brand LED panel, A DIY panel that we made from eBay Strip lights and two Aputure Amaran lights the AL528 and the HR672.

The Cheaper LEDs that we used can are around 70-75. This is ok if you are doing black and white or if you don’t really care about color rendering.

The light bulb measured at 71, the DIY panel at 73 and the non name panel at 76.

The best light came from the Amaran panels with the older AL528 coming at 87 CRI and the newer HR672 coming in at astounding 96.

Here are the test results for the lights we tested listed from top CRI to bottom:

Apature Amaran HR672 CRI = 96
Aputure Amaran HR672 CRI = 96
Apature Amaran AL 528 CRI = 87
Aputure Amaran AL528 CRI = 87
No brand LED light CRI = 76
No brand LED light CRI = 76
DIY panel from eBay / 73
DIY panel from eBay / 73
Cheap LED bulb CRI = 71
Cheap LED bulb CRI = 71
Light pad from rosco CRI = 65
Light pad from Rosco CRI = 65

There you have it. Shop wisely.

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Udi Tirosh

Udi Tirosh

Udi Tirosh is an entrepreneur, photography inventor, journalist, educator, and writer based in Israel. With over 25 years of experience in the photo-video industry, Udi has built and sold several photography-related brands. Udi has a double degree in mass media communications and computer science.

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26 responses to “Not All LED Panels Are Made Equal. Here’s How To Tell The Difference”

  1. Phillip C Reed Avatar
    Phillip C Reed

    OK, CRI is important. We get that. How do you tell what you’ve got?

    1. DIYPhotography Avatar
      DIYPhotography

      Most manufacturers will state their CRI on the box / in the specs / on their website. If they dont… be concerned…

    2. Luc Pilloud Avatar
      Luc Pilloud

      You buy a Lighting Passport and test the Lights before you buy them! ;)

      http://www.LightingPassport.com

  2. Eric Reutlinger Avatar
    Eric Reutlinger
  3. Fazal Majid Avatar
    Fazal Majid

    Theist did you use to measure the specta? Sekonic makes a spectrometer, the C-700, but it costs a cool $1500. CRI is too reductive a number in comparison.

    1. udi tirosh Avatar
      udi tirosh

      Hi Fazal, we used a Lighting Passport Essence: https://www.lightingpassport.com/

      I agree that CRI does not tell the entire story, but it is a very good place to start and if you want a drill down you can look at the individual RAs above

      The LP is similar to the C700 (sans strobe measurement) but still a cool $1500 :)

      1. Fazal Majid Avatar
        Fazal Majid

        I suppose it is consistent with a ~ $1K price for an i1 spectro plus $500 for the LCD and UI. The Colormunki includes a decent spectra for a much lower price, though.

        This gadget may be an alternative for assessing the nature of a light source’s spectrum, for a much more reasonable $100:

        http://www.bhphotovideo.com/c/product/967078-REG/rotolight_rl_spectra_spectrascope_with_leather_case.html

        And a more expensive but probably higher quality instrument from Edmund Optics:

        http://www.edmundoptics.com/testing-targets/spectrometers/handheld-spectroscope/1901/

        1. udi tirosh Avatar
          udi tirosh

          this one looks interesting, though definitely not as accurate :)
          http://store.publiclab.org/collections/spectrometry/products/desktop-spectrometry-kit-3-0

          1. Fazal Majid Avatar
            Fazal Majid

            Great minds think alike. Here’s an even cheaper $5 one that still has a nanometer scale, although the reviews say it’s not so good for older eyes:
            http://smile.amazon.com/EISCO-Premium-Quantitative-Spectroscope-Accuracy/dp/B00B84DGDA/

  4. Alex Avatar
    Alex

    The general point that there are good and bad LED lights is right on, but CRI is the wrong metric for quantifying that in photography. CRI assumes the human visual system in the equation. In photography the camera and/or film see the world differently than humans do. Sometimes very differently. Greater CRI doesn’t necessarily correlate with better color rendering when a digital camera or film are the sensing media.

    1. Burpbeef Avatar
      Burpbeef

      Wouldn’t any decent camera manufacturer “tune” the sensor output to match the response of the human eye? Expeed.. Truepic.. Digic..
      Does the “sensing media” actually matter in such a case?
      And films, well, of course they “tune” the chemistry as well to create something pleasing to a human eye.

      1. udi tirosh Avatar
        udi tirosh

        if an LED light is missing a certain wavelength, you can not “adapt” to it.

        1. oldclimber Avatar
          oldclimber

          Exactly. As manufacturers lump products into bins, i.e. budget = shoplight, worst likely color balance and sold cheap; home upgrade = widest variations, color temps and gizmos attract homeowners but CRI often left off packaging, so not much better than shopgrade; upsale with CRI about 90, looks like it’s great, except R9 can still be near zero, so bold reds look dead brown. Very little incentive yet for brands to care about real color renderings, and standards/indexes/regulations lag way behind. More info is available online but it takes effort to weed out the hype and verbiage. Last, if color matters, find the best bulbs with solid specs and forget about LED lifespan, as real failure rates are likely to be far worse than advertised. If it matters, save all your receipts; saved my butt with the Cree T8 recall and a dozen 4-foot lamps.

      2. oldclimber Avatar
        oldclimber

        Every technology evolved with its own limitations; b&w film was not uniformly sensitive the way eyes are, and filters were routinely used to accommodate that fact. Color films were based on dye layers that were tweaked to best deal with the specified light source. Sensors may be inherently sensitive to a band of wavelengths, so filters physically or electronically modify the result. Human eye output is filtered in myriad complex ways between the retina and any conscious registering of any images, and the brain finishes the editing and manipulations, with many paradoxes and limitations well known to researchers. All the technical wonders now involve rendering product which people find convincing, with no desire to replicate what eyes “see.”

  5. Paganator Avatar
    Paganator

    I wish you showed photos of those colored pencils taken under each different light, so we could tell the difference easily.

  6. Christopher Yule Avatar
    Christopher Yule

    Lots of higher end panels have the information available as it’s a selling point for the monitor. It’s the same for if your displaying photos in a studio etc high cri lamp choices (halogen cri 100, most fluorescents hover around 80) show them off in the best way.

  7. Tristan Robitaille Avatar
    Tristan Robitaille

    Sweet and concise post. Thanks!

  8. Jimmy Fu Avatar
    Jimmy Fu

    i got LED strip with CRI 90-95, R9>60, R12>60, others over 90.

    1. udi tirosh Avatar
      udi tirosh

      HI Jimmy,
      please do share a link :) I would love to see if we can get the word out.

  9. OMla Avatar
    OMla

    Interesting. May I ask you to perform an additional test, by adding a red strip along the normal cool white one? the cool white one will have the spectrum you measured, lacking red, while the red strip will have only that one. Maybe together (after a proper tuning of the relative power) could reach an higher CRI? especially for reds.

  10. Rick Avatar
    Rick

    If I am buying LED bulbs would “natural daylight” bulbs have a better CRI? If my bulb CRI is not good would colour grading after filming help correct things?

    1. Mathew Farrell Avatar
      Mathew Farrell

      Hi Rick, no, “Natural Daylight” just refers to the colour temperature, and has no bearing on the response across the whole light spectrum, which is what we’re ultimately talking about here. Grading can help a little with some issues, but if a range of wavelength (or several) was just not there in the light, nothing was illuminated at that colour, and can’t add it back in artificially. Ditto if some colours were peaking – if they blow out, you’re not bringing them back down.
      Sometimes cheap LEDs look fine to the eye, but the results on camera are bad and not fixable.

      1. Davey Culhane Avatar
        Davey Culhane

        NO bearing on the response across the whole light spectrum ?
        This is confusing me, as I expect CRI and “color temperature” are not independent.
        Wouldn’t “natural daylight” (the sun) have “the full light spectrum” ?