i1 Pro / ArgyllCMS calibration

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Joined: 01/20/2021 - 20:51
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i1 Pro / ArgyllCMS calibration

I'd like to evaluate some LED bulbs that I have, and LED bulbs commonly available in the store in North America, especially those that claim to be "high CRI". I see some pretty great work happening here in terms of measuring and cataloguing the measurement results - probably the best I've seen anywhere on the internet!

I have an x-rite i1 pro (2 of them actually, one Rev A with no UV filter, and one Rev D with UV filter). Using ArgyllCMS, neither one supports Ambient measurement mode (I don't think the Rev A supported ambient mode at all, and I guess my Rev D was sold without the ambient filter, so there's no calibration stored in the device). I can still take measurements using emissive mode in Argyll's spotread, and I seem to be getting sensible results, but I wonder if everything is calibrated correctly. Spotread does perform a calibration using the internal lamp and the calibration base with the white reference disk in it, and the s/n of the base matches the s/n of the unit. Because I don't have the ambient filter cap, I'm just holding the sensor facing the bulb, far enough away to not swamp the sensor. When it's too close, spotread says the results are inconsistent - if I back further away from the bulb, I get readings that seem stable.

I'd like to double check my measurement environment before I use it to start measuring bulbs of interest. I measured a 72w halogen bulb, and these are the results I get. Graphs by importing the .sp file from Argyll spotread into ColorCalculator:

Extended R-Values / CCT / Duv / Ra:

R values:


Spectrum with reference from the TM-30-18 report:

TM-30-18 color vector:

TM-30-18 gamut:

Do these numbers make sense for a halogen bulb?

CCT 3240k

The low R9 (97) R10 (98) and R12 (98)

Rf 99

Rg 99

Duv 0.0013

Should I be concerned about red readings falling off from the reference above 660 nm? The violet readings being lower than the reference below 420nm?

Does this indicate my i1 pro isn't calibrated properly? Can I take this halogen measurement and use it as a correction to apply to other measurements, either in Argyll or ColorCalculator?

Can halogen bulbs have slight variation like this? The bulb does have a light frosting on the inside of the outer glass (as I guess most halogen A19 style bulbs do) - is that contributing?


For poop and laughter, a Utilitech (walmart? I forget where I got them now) crappy 9W 2700k LED bulb (cheapest of the cheap)

Edited by: hwgasdfasdf on 01/21/2021 - 03:16