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Ink stained Fingers

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How does the spectral composition of a gray look like , here is a plot of a very old photographic gray card from Pentax and a gray patch printed with CMY inks on a L1800

Pentax Graycard.png


The spectral response to light is equal at all wavelengths, a graycard like this looks gray under all light conditions since all colors are reflected with the same intensity dimmed by the gray paint. Such a paint is a mix of plenty different pigments, small bumps are visible, and there is a slight fall off at the blue end.

A gray printed with CMY inks looks like this:

L1800 45 Gray.png


The luminance at L=46 is almost identical but strong spectral bumps are visible, and this gray print only looks equal to the above gray card if viewed at the specified white point color temperature - D50 or 5000K in this case. The spectral response differs very much by wavelength, and if you view this gray under different light conditions - daylight - lamplight - it'll change its color tone. This is the reason why it is not recommended to use a CMY mix for gray, it would be much better to have a real neutral base of gray inks and just using CMY colors for small corrections and adjustments of the color response, this is the main reason to introduce gray inks in photo printers improving the situation. Light magenta or light cyan is no remedy in this situation.
I may add some spectral plots with pigment inks and a gray ink later
 

websnail

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I'll try to get hold of an i1Studio/ColorMunki unit.
I've managed to get an i1IO unit (at last!) which is coming with an i1Pro (don't know which type yet) which will be unneeded so once I've tested everything to check it works (assuming it does), you'd be welcome to use the spare unit if that'd help.
 

Ink stained Fingers

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@websnail - thanks for your offer - I picked up an i1Studio just on the last weekend from a friend rather close by.

The revision and type of i1Pro is shown on the unit label

I1Pro.jpg

You may run an initial check with the i1 diagnostics which gives you the starting point of various parameters. The diags supports both the i1Pro and the i1iO table

https://www.xrite.com/de/service-support/downloads/i/i1diagnostics_v4_2_1

Newer diag versions just support newer hardware but not the original i1Pro anymore. The diags run as a standalone program.
Be aware that the combo I1iO/i1Pro is sensitive to the voltage of the USB-port under load - it may work with 4.9 Volt but not with 4.8 Volt anymore, different USB ports on your computer may deliver different values. I have an old i1Pro which only works with an USB voltage above 5.1 Volt. It is the small halogene lamp inside, you get some deposit inside the glass bulb over time, but these little bulbs are not available anymore.

i1Pro-1.jpg

XRite tells you not to run the i1Pro via a USB hub, it works for me - with an external power supply, but these support the 5 Volt condition differently - the above one with 5.40 V, and another power supply only with 4.9 V.
 

Ink stained Fingers

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I still can find them original expensive, alternative not so much.
At what price ? I may need one - whenever .

I was told by several sources that those lamps are not avavilable anymore and service was discontinued for the old i1 spectros already several years ago. X-Rite for sure wanted their customers to upgrade to the newer models instead.
 
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