Is your monitor a high CRI light panel?

[kye]

I saw in a recent YT video by Mark Bone he mentions that he's using his monitor as a light source for the video.

What CRI is a monitor likely to have if it's been calibrated and is of reasonable quality?  Does the fact that it can produce the entire sRGB spectrum (or even a wider gamut) mean that the panel in it has a high CRI?  I'm curious because I do camera tests every now and then and would like a powerful and high CRI light source, and if I already own a really large one then that would be very very handy!!

[no_connection]

No it would have very bad CRI since it's literally a R G and B source fit together in a very tight space. Granted a camera sees R G and B so it might be fine.
Light from a LCD is also polarized which can be useful.

Don't be afraid to use low CRI lights if they give what you are after. And work around the times when they are not.

*edit*

I would theorize that older LCD might have better CRI since they are more washed out and probably covers more of the spectrum when white, on the flipside quantum dot probably is worse due to more saturated and narrow R G and B components.

[androidlad]

25 minutes ago, no_connection said:

No it would have very bad CRI since it's literally a R G and B source fit together in a very tight space. Granted a camera sees R G and B so it might be fine.
Light from a LCD is also polarized which can be useful.

Don't be afraid to use low CRI lights if they give what you are after. And work around the times when they are not.

*edit*

I would theorize that older LCD might have better CRI since they are more washed out and probably covers more of the spectrum when white, on the flipside quantum dot probably is worse due to more saturated and narrow R G and B components.

Nah.

RGB LED backlight was once a very high-end technology reserved only for reference monitors, characterised by three distinct spike in its spectral power distribution. It doesn't have a good CRI due to its discontinuous spectrum, as it's intended to "trick" the human eye which is a tristimulus system (only respond to R, G, B and interpolate everything in between).

High CRI/TLCI requires full spectrum light source and some high end white LED backlight can indeed provide.

[no_connection]

I'm confused, you quote me with a Nah then say exactly what I said.

I don't think anyone used RGB backlight, at least I don't think I saw one. R G and B components comes from the filtered array of pixels, you are going to have that no matter what. But old LCD ( as in old) had more washed out colors so therefore have larger humps instead of spikes, so "better" CRI but are still limited by the CCT driving it.

39 minutes ago, androidlad said:

High CRI/TLCI requires full spectrum light source and some high end white LED backlight can indeed provide.

For the very reason that you need very saturated primaries to produce a wide gamut it will not have a full spectrum once it comes out the front end so I doubt they would waste power to produce it. That is why Quantom dot exist to create very controlled spikes that fit together with the RGB filters. Or rather R G and B Quantum dot cells.

[androidlad]

2 hours ago, no_connection said:

I'm confused, you quote me with a Nah then say exactly what I said.

I don't think anyone used RGB backlight, at least I don't think I saw one. R G and B components comes from the filtered array of pixels, you are going to have that no matter what. But old LCD ( as in old) had more washed out colors so therefore have larger humps instead of spikes, so "better" CRI but are still limited by the CCT driving it.

For the very reason that you need very saturated primaries to produce a wide gamut it will not have a full spectrum once it comes out the front end so I doubt they would waste power to produce it. That is why Quantom dot exist to create very controlled spikes that fit together with the RGB filters. Or rather R G and B Quantum dot cells.

"Camera sees RGB so it might be fine" - Nah it's not fine.

HP, TVLogic and Sony all used RGB LED backlight for their high end products at some point. This is the backlight module with individual RGB LED modules, not RGB pixels in the panel!

Old LCD typically have CCFL backlight, it's even more spikey and discontinuous than LED.

Quantum dot produces even sharper RGB spikes so non of these are suitable as high quality lighting sources.

[Eric Calabros]

On 10/25/2019 at 7:30 PM, androidlad said:

Old LCD typically have CCFL backlight, it's even more spikey and discontinuous than LED.

CFL had actually broader spectrum, but the spike was in green region.

On 10/25/2019 at 7:30 PM, androidlad said:

Quantum dot produces even sharper RGB spikes so non of these are suitable as high quality lighting sources.

You see the filtered light, not the light of backlit itself.

What kye means is that if camera sensor doesn't see the gaps/low intensities in monitor white light spectrum, so it doesn't matter. What really matters is the regions it can see. And thats kind of right, our pixel sensitivity is also a combination of three relatively sharp spikes. 

[androidlad]

4 hours ago, Eric Calabros said:

CFL had actually broader spectrum, but the spike was in green region.

You see the filtered light, not the light of backlit itself.

What kye means is that if camera sensor doesn't see the gaps/low intensities in monitor white light spectrum, so it doesn't matter. What really matters is the regions it can see. And thats kind of right, our pixel sensitivity is also a combination of three relatively sharp spikes. 

BS.

In terms of colour spectrum, the LCD panel has no effect on the backlight, the panel is literally millions of tiny windows that open or close to modulate the backlight.

CFL produces some IR and UV, yes it's broader but they are not in the visible spectrum, and the spikes are all over its SPD.

 

Because our eyes can interpolate colours in between sharp RGB spikes and camera sensor can't, that's a big problem and it does matter.

 

[no_connection]

3 hours ago, androidlad said:

In terms of colour spectrum, the LCD panel has no effect on the backlight, the panel is literally millions of tiny windows that open or close to modulate the backlight.

The panel is literally millions of Red Green and Blue windows.

 

3 hours ago, androidlad said:

Because our eyes can interpolate colours in between sharp RGB spikes and camera sensor can't, that's a big problem and it does matter.

A camera have Red Green and Blue filters in front if the pixels, sounds similar to anything?

I could add that some Tv do have white pixels to add brightness, like some projectors. Think some cameras have done this as well.

[Mads Kristoffersen]

Hi. Sorry to reawaken this threat, but. Would not a HIGH CRI LED backlight produce better image / color quality for the user ?

 

On a separate note, if you sit in front of a led backlit lcd monitor all day, would this be likely to interfere with your sleep pattern ? It's very high in the green and blue spectrum but barely has any of the red.

 

And how does color temperature fit into the picture? Can you get the right color temperatures if the cri is low?