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Tips & Tricks

CRI | The Important Lighting Factor You’re Likely Overlooking When Purchasing A Light

By Kishore Sawh on April 30th 2015

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I remember the incredulous look on the face of my mother and family, when they learned that part of my uppity all-boys private school education was to spend a considerable amount of time at one point, on the hazards of drugs. But I sort of understood because I used to while away some of my homework hours listening to Dark Side Of The Moon. If you were a young person in the 70s, you didn’t need this sort of education because Pink Floyd was a living beacon of what recreational drugs could do to a person.

That album cover also happened to be some introduction to understanding light, weirdly. The famous beam of light hitting a Prism then showing the rainbow of colors within the beam coming out the other side. If you’re a freak, like me, you’ll probably estimate that that light bean is sunlight given the evenness of the colors coming from the other side. This brings us neatly to the often overlooked topic of the Color Rendering Index (CRI), and how its ratings are of far more importance than most tend to give them in the photographic world.

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When thinking about light and light sources, we tend to think about them in terms of intensity, power, and temperature. This is all well and good and those are important factors to consider, but perhaps just as useful would be the measure of a light source’s color characteristics in terms of a CRI rating. In the most simple terms, CRI measures the ability of a light source to show an object’s color naturally or ‘realistically,’ typically measured compared to a standard reference source like daylight.

A CRI of 100 is the maximum and more perfect value, and you’ll typically get very high ratings in the high 90s from an incandescent light source, but fluorescent and LED lights typically have a much lower rating – between 60 and 75, from my experience. Generally, you’re looking for 85 and above for a good light for photography. So, the good folk over at DIY Photography have put together a video and associated post explaining a bit more about CRI, why it matters, how it’s measured using a Spectrometer, and how you can test it.

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They’ve also tested various LED light panels to show how they are not all made equal. The cheapest of the lot came in around 71, and the most elite was 96, which is highly impressive. (Incidentally, the new Icelight V2 has a CRI of 96 also which is partially why it’s so impressive – learn about it here). It’s great to see on video just how much of a difference a high CRI rating makes a picture, and this is something that should be considered with every light you buy, especially in this age of LED product proliferation.

See the full post here, and the video below.

Source: DIYPhotography

About

A photographer and writer based in Miami, he can often be found at dog parks, and airports in London and Toronto. He is also a tremendous fan of flossing and the happiest guy around when the company’s good.

Q&A Discussions

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  1. Joseph Prusa

    Ice light is nice

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  2. Robert Sheppard

    Interesting information, especially as I am considering an LED light. Thanks

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  3. Ralph Hightower

    Kishore:
    Yes, I concur. Pink Floyd was one of my favorite groups.

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  4. Graham Curran

    Really informative post, thanks.

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  5. Dave Kai Piper

    Great post !! Loved and shared !

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  6. Karthik Thorali

    Hi,
    Is there a way to measure / validate CRI for light source as LED ?

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    • Jeff McCrum

      Not really, as manufacturers know what the meters are looking for. With specific phosphor mixes on the LED chips to create the white light they can tweak to specific wavelengths in the 15 colors and let the spaces in between and ends of the spectrum taper off. If you look at the colors involved with CRI they’re mostly pastels (http://www.gc-lighting.com/wp-content/uploads/GREEN-CREATIVE-CRI-website22.png), there’s no clean blue, no orange, a single red. They are mostly about tones used in an office setting. Photography deals with a wide array of color and when you have millions of dollars at stake there has been a lot of tweaking to game the system and provide a high CRI source that doesn’t really look good to the eye.

      Additionally, CRI doesn’t take color temperature into account. Nor does it acknowledge color consistency. So they can send a 4100K batch with the best spectrum they can collect and then have things average out over the long run.

      There was a new measurement system (called CQS) that was proposed but about two months ago the CIE stopped bothering moving forward since it couldn’t get out of committee. So CRI is the only way we can scientifically measure things right now, but again, that doesn’t mean it’s the best way. You have to power things up and determine if it’s right for you and your work the same way you have to shop for any camera gear and determine if it works for you.

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  7. Lauchlan Toal

    So maybe there is a difference between different brands of strobes… Would love to see how the CRI’s of Broncolor, Profoto, Elinchrom, and PCB compare.

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    • Stan Rogers

      They’ll all test out to 100 since they’re all continuous spectrum (as is tungsten). That doesn’t make them the same; it just means that they can be profiled and/or gelled (at the used power) to give the same end result. Most strobes/flashes change colour considerably at different power settings (while retaining their 100 CRI, which has nothing to do with colour temperature). A few are much more consistent within a specific range (Broncolor’s Scoro and Siros, Elinchrom’s new ELC Pro HD, some Hensels, PCB’s Einstein), but outside of that range still need to be gelled for power differences between heads (and for modifiers) if colours are critical. (And sometimes the differences are *extemely* predictable; almost all speedlights need 1/4 cut of CTS per stop down. So if you’re using one speedlight at half power and another at 1/4 power, you’d need a 1/4 cut of CT straw on the 1/4-power unit to make them the same colour. CTO is usually too red unless you’re dealing with 2-1/2 stops or more difference.) Except in product photography, though, one doesn’t usually deal with wild power differences and critical colour at the same time; warmer highlights and cooler shadows are, often as not, a desired outcome rather than a problem to be fixed.

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  8. Ben Perrin

    Interesting. Still wouldn’t pay so much money for an ice light though. Maybe I missed it but does something like the colour checker passport make this a moot point?

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    • Jeff McCrum

      No. Because the source literally cannot create all the light wavelength colors in the first place the colors therefore cannot bounce off the objects and into the camera.

      If we gel a light to filter it so that only red wavelengths come out and then shine it on a blue object, it will appear black because there are no blue wavelengths in the first place. Colour checker passports will correct for color temperature and things like that, but they cannot add color into the scene that wasn’t there in the first place.

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    • Ben Perrin

      It’s not just white balance they do, they have a look at colour values (from the passport) and manipulate those colours to look like the real world values. Not saying that they are the best option, obviously getting it right in camera is the best option just wondering if they can minimise the difference to the point where it’s not worth the money to purchase more expensive lights. Just a thought anyway…

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    • Jeff McCrum

      They’ll help, but if the color isn’t rendered in the first place you can’t get it back in. You can push saturation or tweak hue, but it seems like a lot of work when you could just use a non-LED source to do the same thing in the first place.

      CRI’s in the 80’s, which is where you’ll find most LED sources, are decent for most uses, but that last 15% is going to be noticeable. And, since tungsten-halogen or xenon flash is still less expensive than LED, you’re probably better off just using it for projects that are really important.

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  9. Rafael Steffen

    Thanks for sharing this detailed explanation about lighting. This helps to understand the quality of light as Cliff Mautner once explained me.

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  10. Jeff McCrum

    Also, please keep in mind that CRI is only a specific scientific metric that was developed long before we had the capabilities to tune specific wavelengths to game the system. CRI was developed for fluorescents and we still do not have a good metric for LED.

    Test it with your eye and your camera, don’t just read the specs.

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    • Thomas Horton

      I can have 100.1% CRI in my lighting. But if I don’t know how to use it….

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    • Jeff McCrum

      Can’t that be said of any camera gear? Who hasn’t seen the person with the $5,000 camera that they don’t move off the green box setting?

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  11. Ed Rhodes

    lots of great info!

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  12. Keith Starkey

    Great information, what with the popularity of LEDs and all becoming quite the thing. Thanks!

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  13. Brandon Dewey

    great video

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