Confusion about calibrating x-rite 880 890 892 etc.

[czygeorge]

Hi all~

We use an old x-rite 892,and you know it needs to be calibrated by a 880-100 strip.

Like many its owners we don't have this calibrating stripsAnd I guess those stock may get faded with aging too

So a friend of mine are trying to print it by our own and use manual calibrate function(you can input the rgb densities of the calibrating strip's white space by your own) to do this job

What confused us is:
Now the density reading we or printing factory use should be CMY channel.And the reflection densitometer we used for reading the correct densities of the paper will only give CMY result

And this x-rite 892 use rgb.

Is this rgb actually means cmy in the paper and you can just input the cmy of the paper reading than it should be OK?

Btw we are very surprising that this densitometer only use white spot calibrating
And not only 880 892 for control strips reading, we found those x-rite 1990s densitometer all have very different reading results from one paper when not get calibrated

Unfortunately a x-rite 820 is so expensive and rare.And the lamp of this desitometer are also a headache too

Any thoughts or advices would be fully appreciated !
Thanks a lot

A picture of the strips he printed

 

[Mr Bill]

What confused us is:
Now the density reading we or printing factory use should be CMY channel.And the reflection densitometer we used for reading the correct densities of the paper will only give CMY result

And this x-rite 892 use rgb.

Hi, offhand I'm not very familiar with the X-rite 892.

But some densitometery background: In color photography the film or paper generally uses dyes called cyan, magenta, and yellow, the so-called subtractive primaries. The normal color densitometers can isolate (sort of) and measure the optical density of each of these dyes.

They do this by (essentially) inserting a hard-cutting color filter into the optical path; the filters are called red, green, or blue. These filters each allow only a narrow spectral band through, thus the densitometer is only able to "see" a narrow spectral range for each color.

When we do traditional color "process control," here's what basically happens. We process the so-called "control strip" which is pre-exposed by the manufacturer. We then read it using a color densitometer. To read the amount of cyan dye the densitometer uses the red filter. We traditionally call this "the red density" and plot it on the chart with a red line. But it is actually a measurement of the cyan dye density.

Similarly the "green density" is measured by inserting a hard-cutting green filter into the optical path, and this measures the magenta dye. Finally, the blue density uses a blue filter, and measures yellow dye.

So in other words, in color photography, we are actually measuring the densities of the cyan, magenta, and yellow dyes by using a red, green, or blue filter, respectively, in the densitometer's optical path. But we generally refer to the reading as "red," "green," or "blue" according to the color of the filter used.

In order to understand HOW this works you probably need to see spectral graphs of the dyes and then think things through. (If you use Kodak Wratten printing filters (cyan, magenta, and yellow) they'll have curves for different values, where, for example, a 30cc filter would read about 0.30 on a densitometer. So you could actually work through the calculations if you wanted to.)

The color densitometers used in photography should probably be what they call Status M for color negatives, or Status A for reversal (slide) films and color papers. These define the narrow spectral bands that the densitometer should be able to "see." Which is roughly what the red, green, and blue filters let through.

I know this is a lot to swallow at once if you're new to this. I'll be glad to explain further if you'd like.

 

[czygeorge]

Hi, offhand I'm not very familiar with the X-rite 892.

But some densitometery background: In color photography the film or paper generally uses dyes called cyan, magenta, and yellow, the so-called subtractive primaries. The normal color densitometers can isolate (sort of) and measure the optical density of each of these dyes.

They do this by (essentially) inserting a hard-cutting color filter into the optical path; the filters are called red, green, or blue. These filters each allow only a narrow spectral band through, thus the densitometer is only able to "see" a narrow spectral range for each color.

When we do traditional color "process control," here's what basically happens. We process the so-called "control strip" which is pre-exposed by the manufacturer. We then read it using a color densitometer. To read the amount of cyan dye the densitometer uses the red filter. We traditionally call this "the red density" and plot it on the chart with a red line. But it is actually a measurement of the cyan dye density.

Similarly the "green density" is measured by inserting a hard-cutting green filter into the optical path, and this measures the magenta dye. Finally, the blue density uses a blue filter, and measures yellow dye.

So in other words, in color photography, we are actually measuring the densities of the cyan, magenta, and yellow dyes by using a red, green, or blue filter, respectively, in the densitometer's optical path. But we generally refer to the reading as "red," "green," or "blue" according to the color of the filter used.

In order to understand HOW this works you probably need to see spectral graphs of the dyes and then think things through. (If you use Kodak Wratten printing filters (cyan, magenta, and yellow) they'll have curves for different values, where, for example, a 30cc filter would read about 0.30 on a densitometer. So you could actually work through the calculations if you wanted to.)

The color densitometers used in photography should probably be what they call Status M for color negatives, or Status A for reversal (slide) films and color papers. These define the narrow spectral bands that the densitometer should be able to "see." Which is roughly what the red, green, and blue filters let through.

I know this is a lot to swallow at once if you're new to this. I'll be glad to explain further if you'd like.

Dear Bill

Really really thanks for your so deeply and warmfull explanation
Now I totally get it!And all my confusions are resolved
Thanks again

Best
George

 

[Mr Bill]

You're quite welcome George. If you have any other questions feel free to ask (I have set an alert to watch this thread).