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REVIEW: HP ZR2440w Part 6

Luminance distribution and colour homogeneity

We test the luminance distribution and image homogeneity using a white test image, on which we carry out measurements at 15 points on the screen. The luminance deviation (in percent) and DeltaC (i.e. the difference in colourfulness) are then derived with regard to the value measured in the centre of the screen.

Left: Luminance deviation, right: colour homogeneity for a white test image.

The HP ZR2440w’s luminance distribution and colour homogeneity are not quite as pleasing as its illumination, black point and contrast. The average luminance deviation is 6,1 percent, whereby the largest deviations are at the top towards the sides. However, these deviations do not exceed the limit of 20 %, beyond which they would be visible.

When we tested the colour homogeneity, we measured a DeltaC deviation of more than 3 in the lower left and right corners in particular. Interestingly, however, no colour tints are visible with the naked eye on a white test image.

Viewing angle

One of the characteristics of an IPS panel is a very stable viewing angle, which means that even when the viewing angle is changed from the centre, even to a great extent, the colour reproduction remains constant and only the contrast decreases. On the HP ZR2440w, colour deviations cannot be seen from any viewing angle, but from wider viewing angles the contrast decreases.

Viewing angle of the HP ZR2440w.

Colour reproduction

With monitors intended for consumer and office use, we first test the colour reproduction in the factory settings after the reset and also in sRGB mode, if there is one. Finally, the monitor is calibrated using Quato iColor display. We use our own software for the measurements and an X-rite DTP94 as a measuring device as well as an X-rite i1 Pro spectral photometer.

sRGB: 92 % colour space coverage

With 92 percent coverage of the sRGB working colour space, the HP ZR2440w achieves a good level for a monitor with an LED backlight and is just 2 percent behind the HP ZR24w with its CCFL backlight. However, the undercoverage is more in the blue area with this model as well.

Video: Coverage of sRGB colour space (Explanation of 3D views).

We have summarised the explanations of the chards below: DeltaE deviation for colour values and white point, DeltaC deviation for grey values and gradation.

Comparison of factory settings with the sRGB working colour space

In the factory settings, the "Standard (6500K)" image mode is selected. Without making any changes, we carried out measurements on this image mode: the grey axis is very neutral and 8is well set up. The contrast ratio of 1099:1 is also convincing. The DeltaE of the colour values is rather high, especially for blue and green, which indicates an undercoverage in these colour sectors. The white point is somewhat too warm at 6251 Kelvin, whilst the gradation is too low at an average of 2.09.

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