SpyderX Delta E Calculation Mismatch – Need Help!

[yulincoder]

I have been researching color measurement using the SpyderX Elite.
I have some very confusing questions about it. Can someone help me? Thanks!

I found that when using the SpyderX to obtain Delta E values, my own calculations do not match the results from Spyder's official software. Specifically, when I read data from the SpyderX (using the open-source code for hacking SpyderX on GitHub), my Delta E values differ from those reported by the official software.

Example

• Test sample: Lab = [83.61, 3.36, 87.02]
• Tested generated image's RGB: (243, 205, 7) (I took a screenshot)
• Delta E from official software: 0.27

However, in my own calculations:

1. I obtained the primary chromaticity coordinates (xy) as:
   • [0.623570, 0.298768]
   • [0.310583, 0.593947]
   • [0.120839, 0.069452]
2. I measured the XYZ values of a pure white (255, 255, 255) image using the SpyderX:
   • [390.636366, 414.663251, 498.881663]
3. I measured the XYZ values of the test image (243, 205, 7) using the SpyderX:
   • [247.880162, 252.762201, 49.025823]
4. My calculated Delta E: 2.763

I've attached my code below.

Can anyone help me understand why my results differ from the official software?
Thank you very much!

import numpy as np
import colour

# Define colour cards with Lab and spyderx values
colour_cards = {
    "card3": {
        "Lab": np.array([83.61, 3.36, 87.02]), # Test Sample Lab, its RGB is [243, 205, 7] in myapple
        "spyderx_wp": np.array([390.636366, 414.663251, 498.881663]),
        "spyderx": np.array([247.880162, 252.762201, 49.025823]),
    },
}

# Calculate and print delta E for each card
for card, value in colour_cards.items():
    print(f"{card} --------------------------------")
    methods = ["CIE 2000", "DIN99"]
    spyderx_Lab = colour.XYZ_to_Lab(
        value["spyderx"] / value["spyderx_wp"][1], 
        colour.XYZ_to_xy(value["spyderx_wp"])
    )

    for method in methods:
        deltaE = colour.delta_E(value["Lab"], spyderx_Lab, method)
        print(f"{method} : {deltaE}")

output

card3 --------------------------------
CIE 2000 : 2.7636120152160455
DIN99 : 2.3592621541713523

[yulincoder]

[KelSolaar]

Hello @yulincoder,

I'm actually not too sure, do you know what is the RGB space of the (243, 205, 7)? It does not look like sRGB or Display P3.

Cheers,

Thomas

[yulincoder]

Hello， @KelSolaar

Thank you very much. I suspect the official Spyder software might be referencing my computer's ICC profile to calculate RGB values. Attached is my current display color profile:
AppleColorLCD-spyder-250305-sRGB.icc.zip

Given that I've already obtained the XYZ measurements for both the white reference card ("spyderx_wp") and the test color card ("spyderx") displayed through SpyderX software, would it be appropriate to directly convert these XYZ values to Lab using colour.XYZ_to_Lab without considering the color space context?

Best
Yulin