Colour temperature calibration?

Hi Ken,

If you put the same voltage into the three electron guns in your monitor you’ll get about 9300 Kelvin. To get D50 you’ll have to run the red gun at a much higher level than the other two. The red phosphors in the tube begin to fade and need more and more power to get a particular color. Eventually you can’t get a bright red, even running the red gun at 100%, without darkening the other two colors to the point that the monitor looks dark.

In a high-end production facility they often calibrate their monitors to D50 and replace them every year or so. For the rest of us, D65 is a good compromise.

Tom Nelson
Tom Nelson Photography

In article <46ab3bb2$0$15276$>, Ken
wrote:

From what I have read, 5000K (D50) seems to be the standard for viewing booths and 6500K (D65) the standard for monitors.

Why, if D50 is the standard for viewing prints, isn’t D50 the preferred temperature for monitors?

Ken

On Jul 30, 12:11 pm, Tom Nelson
wrote:

Hi Ken,

If you put the same voltage into the three electron guns in your monitor you’ll get about 9300 Kelvin. To get D50 you’ll have to run the red gun at a much higher level than the other two. The red phosphors in the tube begin to fade and need more and more power to get a particular color. Eventually you can’t get a bright red, even running the red gun at 100%, without darkening the other two colors to the point that the monitor looks dark.

In a high-end production facility they often calibrate their monitors to D50 and replace them every year or so. For the rest of us, D65 is a good compromise.

Tom Nelson
Tom Nelson Photography

In article <46ab3bb2$0$15276$>, Ken

wrote:

From what I have read, 5000K (D50) seems to be the standard for viewing booths and 6500K (D65) the standard for monitors.

Why, if D50 is the standard for viewing prints, isn’t D50 the preferred temperature for monitors?

Ken

Thanks Tom

Thanks, Tom.

Is the problem unique to CRT monitors or does it also apply to LCD monitors?

Ken

In article <300720071211370170%>,
Tom Nelson wrote:

Hi Ken,

If you put the same voltage into the three electron guns in your monitor you’ll get about 9300 Kelvin. To get D50 you’ll have to run the red gun at a much higher level than the other two. The red phosphors in the tube begin to fade and need more and more power to get a particular color. Eventually you can’t get a bright red, even running the red gun at 100%, without darkening the other two colors to the point that the monitor looks dark.

In a high-end production facility they often calibrate their monitors to D50 and replace them every year or so. For the rest of us, D65 is a good compromise.

Tom Nelson
Tom Nelson Photography

In article <46ab3bb2$0$15276$>, Ken
wrote:

From what I have read, 5000K (D50) seems to be the standard for viewing booths and 6500K (D65) the standard for monitors.

Why, if D50 is the standard for viewing prints, isn’t D50 the preferred temperature for monitors?

Ken

Ken wrote:

Why, if D50 is the standard for viewing prints,
isn’t D50 the preferred temperature for monitors?

There is no single answer to that:

1) D50 _is_ the preferred CCT for monitors of most of the people who use D50 viewing booths (people who deal with material that is going to be printed).

2) in the past there was no ("full spectrum") D65 fluoresecent lamps and filtering Tungsten to D65 is way more inefficient than to D50.

3) The chromatic adaptation of the vision is still not fully understood/characterized.

4) People only rarely view prints under D65 (open shadow on sunny day), mostly they view them under 2850K … 4000K. So even the 5000K is pretty high for the purpose of simulating the actual viewing experience. But lesser than 5000K for the viewing boot is troublesome in respect with color management … already the 5000K looks a little yellowish (to many).

5) With monitors, there is not many practical needs to limit the CCT of the whitepoint to D50, monitors can as easily produce CCT of D65 as well. The only need that I can figure out is the (supposed) need to match the viewing booth color temperature. D65 is, for many, very very pure white. And D50 is, for many, a little yellowish white, it is about the white that you see when you look a normal xerox copypaper that is illuminated by the direct sunshine. In case the monitor whitepoint is set to D65 then it can show the very pure white efficiently (all channels at max), and it can show rather high luminance D50 also very efficiently (mainly the blue channel is scaled down a little, and this has only a small effect to luminance). But a monitor that is set to D50 can not show the color of D65 at high luminance at all (both red and green channels need to be scaled down and that eats a lot of luminance). So, when a monitor is set to D65 it can show different kind of images more efficiently than a monitor that is set to D50 (where often luminance has to be sacrificed in favor of more pure whites).

Timo Autiokari

Timo

Thanks for the response.

Point #5 is going to take me a while to digest. I have a lot to learn 🙁

Ken

"Timo Autiokari" wrote in message

Ken wrote:

Why, if D50 is the standard for viewing prints,
isn’t D50 the preferred temperature for monitors?

There is no single answer to that:

1) D50 _is_ the preferred CCT for monitors of most of the people who use D50 viewing booths (people who deal with material that is going to be printed).

2) in the past there was no ("full spectrum") D65 fluoresecent lamps and filtering Tungsten to D65 is way more inefficient than to D50.
3) The chromatic adaptation of the vision is still not fully understood/characterized.

4) People only rarely view prints under D65 (open shadow on sunny day), mostly they view them under 2850K … 4000K. So even the 5000K is pretty high for the purpose of simulating the actual viewing experience. But lesser than 5000K for the viewing boot is troublesome in respect with color management … already the 5000K looks a little yellowish (to many).
5) With monitors, there is not many practical needs to limit the CCT of the whitepoint to D50, monitors can as easily produce CCT of D65 as well. The only need that I can figure out is the (supposed) need to match the viewing booth color temperature. D65 is, for many, very very pure white. And D50 is, for many, a little yellowish white, it is about the white that you see when you look a normal xerox copypaper that is illuminated by the direct sunshine. In case the monitor whitepoint is set to D65 then it can show the very pure white efficiently (all channels at max), and it can show rather high luminance D50 also very efficiently (mainly the blue channel is scaled down a little, and this has only a small effect to luminance). But a monitor that is set to D50 can not show the color of D65 at high luminance at all (both red and green channels need to be scaled down and that eats a lot of luminance). So, when a monitor is set to D65 it can show different kind of images more efficiently than a monitor that is set to D50 (where often luminance has to be sacrificed in favor of more pure whites).

Timo Autiokari

Good question, Ken. I would think LCD monitors would be immune but I don’t know for certain. Does anybody else here know?
Tom Nelson
Tom Nelson Photography

In article , Ken
wrote:

Thanks, Tom.

Is the problem unique to CRT monitors or does it also apply to LCD monitors?

Ken

In article <300720071211370170%>,
Tom Nelson wrote:

Hi Ken,

If you put the same voltage into the three electron guns in your monitor you’ll get about 9300 Kelvin. To get D50 you’ll have to run the red gun at a much higher level than the other two. The red phosphors in the tube begin to fade and need more and more power to get a particular color. Eventually you can’t get a bright red, even running the red gun at 100%, without darkening the other two colors to the point that the monitor looks dark.

In a high-end production facility they often calibrate their monitors to D50 and replace them every year or so. For the rest of us, D65 is a good compromise.

Tom Nelson
Tom Nelson Photography

In article <46ab3bb2$0$15276$>, Ken
wrote:

From what I have read, 5000K (D50) seems to be the standard for viewing booths and 6500K (D65) the standard for monitors.

Why, if D50 is the standard for viewing prints, isn’t D50 the preferred temperature for monitors?

Ken