Quick test of the Medialight Pro 6500K CRI99 Bias Light strip

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maukka
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Quick test of the Medialight Pro 6500K CRI99 Bias Light strip

There isn’t a suitable forum for LED strips so here it goes.

I got a sample of the Medialight Pro 6500K CRI99 LED light strip for bias lighting monitors and televisions. This is a feature that decreases eye strain in a completely dark room so that the (relatively) small viewable display area is not the only bright thing in your field of view. To my knowledge Philips is the only TV manufacturer with a built-in bias lighting system (Ambilight). Aftermarket kits are available and they can even be programmed to dynamically react to the content on screen when you wire the HDMI signal through the bias light controller.

The Medialight Pro is a single color bias light with PWM dimming. I don’t know the manufacturer of the violet (~400nm) pumped LEDs. Despite the similar package size they are not Yuji VTC series, that’s for sure.

Long story short and measurements right after the observations:
- Excellent CRI (Ra 98, R9 98, TM-30-15 Rf 97, Rg 99)
- Tad greener than D65 (which the light is supposed to mimic)
- PWM controller is too slow in frequency (~150Hz) to be used on any other mode than max (click for video https://imgur.com/uVcJ59W)
- Power consumption on max is 2.6 watts (0.49A at 5.3V)
- Power consumption on min is 82mW (15.4mA at 5.3V)
- Power consumption on standby is 30mW (5.6mA at 5.3V)


Contrary to what it might look like here, all the LEDs are identical in color temp.


Image adjusted to be closer to what it actually looks like. My monitor is actually calibrated to 6150K, not D65.


The violet pumped LEDs produce a stunning spectrum with super high CRI as promised.


Bouncing it off of my Grandview projection screen gives the light a bit of greenish tint, which would be visible compared to a D65 calibrated monitor.


XY coordinates on CIE1936 chart compared to the D65 illuminant. The greenish tint would benefit from a slight magenta tint to the wall the light is bounced from.

Edited by: maukka on 10/08/2018 - 16:19
SKV89
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Very interesting. I would love to see more of these. If these were 3000k and below BBL, I would buy a set right away.

DavidEF
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SKV89 wrote:
Very interesting. I would love to see more of these. If these were 3000k and below BBL, I would buy a set right away.

Better would be the use of multiple CCT emitters with the ability to adjust to match your screen/monitor. Since monitors can be adjusted to different CCT by the user, it would be great if these could be as well.

Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone.
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Jerommel
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Wow, that’s quite a UV spike these things emit..

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Jerommel wrote:
Wow, that’s quite a UV spike these things emit..
Well, it’s around ~400nm so not bad, really. Probably makes things more interesting to look at, really. Cool

Reason is not automatic. Those who deny it cannot be conquered by it. Do not count on them. Leave them alone.
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maukka
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There certainly is some borderline UV, but the actual energy even at the 400nm peak isn’t very high, especially when used in its intended purpose behind a tv and bounced. If you’re worried, then you probably have your curtains pulled closed during the day as well Smile

Here’s the spectrum compared with and without polycarbonate saftely glasses to block actual UV. Doesn’t affect CRI.

Jerommel
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The peak is huge compared to the Yuji VTC D50 or sunlight.

I have a 400NM light for curing glue, and it’s not pleasant when you look at the output.

maukka
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Sure the relative peak is higher but the energy is not. Just tested and even a dim sunlight through a thick cloud cover in the morning has more absolute 400nm content than this when bounced from a wall and observed from 40cm which is not realistic.

Of course you shouldn’t look straight into the LEDs without filtering.

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My point is that relative values are more important because your iris accommodates to the full spectrum.

maukka
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A bias light is supposed to be about 10% of the maximum brightness of the television. In most situation the visible light from the display will trump the output of the bias light.

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Yes, in the application for which it is intended, you’re right.
I was thinking about when you use it for work light or whatever else we can come up with.
In such case i would prefer to use a UV filter.

I wonder if these LEDs also light up fluorescent objects (white paper, yellow objects etcetera) considerably more than low / no UV LEDs.