We have based our test method around an X-Rite i1 Display Pro colorimeter and an X-Rite i1 Basic Pro spectrophotometer, which we can use to calibrate the colorimeter for every monitor test. Using our self-made accessory (long live 3D printers) we can use this colorimeter to measure the viewing angles. For the analysis of the data we use a new workflow developed in SpectraCal Calman 5.
We test monitors on a great number of aspects. We measure them 'out of the box', but if they have an sRGB-mode we test this separately. This is also the case with an AdobeRGB-mode. An exception to this are the monitors that are clearly adjusted for a wider colour space out of the box – in this case we measure using a corresponding colour space. The standard one we use is the sRGB-triangle.
We use our colorimeter to set the monitors to a brightness of 150 cd/m² (or a value that comes as close to this as possible). This brightness is representative for what you will use in most scenarios in a normally lit room, and can be displayed by practically every monitor. By configuring all monitors to the same brightness of white, we create an equal playing field. Of course we still measure the maximum brightness, as well as the corresponding contrast and power consumption. Below we will briefly discuss the different segments of the test.
Brightness and contrast
We measure brightness and contrast in both 150 cd/m² and the maximum brightness, as well as the black values in both settings. We also look at the minimum brightness, in other words the brightness of white when we change the monitor brightness to its minimum level. Aside from that we measure the contrast between a white and black surface, surrounded by a 50% grey surface (transverse measurement), the checkerboard contrast with a 5x3 raster of alternating white and black fields, and the maximum contrast between a fully white and fully black surface.
For the uniformity we first look at the ratio between the lowest brightness in a white area compared with the highest measured brightness, expressed as a percentage. For example: the least bright part of the screen was 77% of the brightness of the brightest part. We also measure the ratio between the average of a measurement of 15 points and the highest brightness. Aside from that we perform the uniformity measurement with a black surface as well, showing severe clouding and backlight bleeding – if it is present. All uniformity measurements result in five screenshots per tested monitor: the uniformity of black, white, the contrast ratio at all (15) points, the colour temperature uniformity and the relative colour differences in comparison with the middle, expressed as DeltaE-value
Of course it is best when you are sitting right in front of a monitor, but what if you are not? In order to find out how a monitor performs under a sharped viewing angle, we measure the remaining brightness and colour shift compared with the middle under an angle of 45 degrees, expressed as DeltaE-value. This is based on the average of red, green, blue, cyan, magenta and yellow, plus 100% and 75% white. Because we also calculate the standard deviation of those sub measurements, we can also give an indication on whether or not a colour shift takes place: a big standard deviation means that one or more sub measurements deviates quite a bit, which means that a colour shift takes place.
Aside from the average colour deviation we also show the deviation of grey compared with the middle from all of the four measured angles. We do this for every tested product using a screenshot. A possible colour shift becomes clear when you look at this screenshot.
We perform colour measurements using CIE2000. This measurement is based on a large amount of sub measurements, the so-called ‘Colour checker’ which looks at a lot of common hues. Once again we show the standard deviation as well as the average deviation, to give an impression of the amount of fluctuation of our measurements. A smaller number means there is a more constant degree of deviation. This is also the case for our grayscale measurements, that we perform in twenty steps for a more accurate result. With every tested product we also show a screenshot of a so-called saturation sweep in order to show the deviation of the base- and support colours in the entire colour space. Of course you can also find screenshots of the colour measurement and colour checker results for every tested product.
We have added measurements of a white and black screen at 150 cd/m² to the existing measurements at 100% brightness (white, black, standby and off). This will show a more realistic image of the actual power consumption of the tested monitors.
For gaming purposes we test response times and input lag. For this we still use a photo sensor with a Waverunner 6100 oscilloscope, and a combination of a Leo Bodnar input lag tester and a comparison with a CRT-monitor respectively.
The test method generates a lot of new data. For now we have chosen to add and show this data in its entirety via our database. As a direct result our pages with the test results of monitors are very long. We have tried to keep it as clear as possible with by separating the data in smaller blocks. The reaction times and input lag are shown first, followed by the power consumption. After that there is a small block with the basic results of brightness and contrast, followed by a larger block with the uniformity results. Next up are the viewing angle values and following that are the colour measurements in the default view. If the monitor has an sRGB-mode, an identical block is shown with the results of the measurements using that mode; the same is be done for AdobeRGB-mode if possible.
For this review we compare the AOC I2490PXQU, I2790PQU and Q2790PQU with a selection of competitors we also tested. Most of those are found in the 24-inch full hd and 27-inch qhd-segments, but we also have some comparison material for the 27-inch full hd variant. This can be recognized by the black bars in the graphs on the next pages; the green bars are the 27-inch qhd monitors, the blue are 24-inch full hd. The three AOC models are red in the graphs.