REVIEW: NEC PA241W Part 8

Additional losses arise for deviations from the native white point (screens with RGB LED backlighting are an exception). In the case of the calibration to D50 as a white point and with ColorComp at Level\ 3, we measure a black point of 0,29 cd/m² at a luminance of 140 cd/m2. The contrast is thus almost 520:1. The same settings for light density and ColorComp give rise to a black point of 0,21 cd/m² at a white point of D65. The contrast ratio in this case is thus around 660:1. In the image mode "FULL", the contrast ratio for the minimum light density of 39 cd/m² is around 260:1 (ColorComp: Off).

Illumination of the monitor for short exposure time (left) and long exposure time (right).

Brightness distribution

We examined the brightness distribution and image homogeneity on a white test picture, taking measurements at 15 points on the screen. This gives rise to the luminance deviation in percent and the DeltaC (i.e. the difference in chrominance) with regard to the value measured in the centre. For the DeltaC, the threshold for perception, using achromatic colours as a reference, is already 0.5. A DeltaC of 4 should not be exceeded by a significant amount – otherwise, stronger colour tints will arise. Comparing the correlated colour temperature (CCT) in Kelvin does not make any sense. This measurement only indicates the colour temperature of a black image, which is the most similar to the concrete colour test. Thus, the colour values from two tests with an identical CCT can be considerably different from each other.

The luminance distribution (left picture) and image homogeneity (right picture) were measured at 15 points on the screen - ColorComp off.

The luminance distribution (left picture) and image homogeneity (right picture) were measured at 15 points on the screen - ColorComp 5.

The deviations measured in luminance and homogeneity are at a rather mediocre level for a model of this performance and price class when ColorComp is not activated. With regard to the image homogeneity, this applies to the upper right hand section in particular. Fortunately, the image changes dramatically when ColorComp is activated. In the highest setting, the NEC PA241W achieves an outstanding result. The slight losses of contrast should certainly be accepted in return for this clear improvement. At this point, it should be noted that NEC is the only manufacturer we know of which allows the user the use of an existing compensation function at all – i.e. the only one who does not activate this without offering a choice.

Viewing angle

The manufacture’s indication for the maximum viewing angle is 178 degrees horizontal and vertical. The values indicated are based on a resting contrast of 10:1. These values are typical for modern IPS and VA panels. TN panels also achieve similar viewing angles on paper, but at a resting contrast of 5:1. Thus, the values are not comparable. In addition, other colorimetric changes are not considered in the measurements.

Therefore, the actual, subjective viewing angle stability without visible colour errors, negative effects or changes to other image parameters is more important than the viewing angle indication with respect to the resting contrast.

Viewing angle on the NEC PA241W.

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