HDR Measurements & Hands-On
To test the S2718D’s HDR feature, we had to add a new device to our calibration toolkit: the HD Fury Integral. It’s a small box that modifies a 1080p SDR signal by adding the appropriate HDR10 metadata. We connected it between our Accupel pattern generator and the display. We also used a special CalMAN workflow designed specifically for HDR10 calibrations. It measures the proper EOTF luminance tracking function, as well as Rec.2020, DCI-P3, and Rec.709 color.
When it comes to the S2718D it’s important to note two things: it must be switched manually into one of its two HDR picture modes before sending the signal; and there are no image adjustments available in either Movie HDR or Game HDR. What you see is what you get. It also engages dynamic contrast even though the OSD option is grayed out. We could see brightness pumping when switching quickly between patterns of varying brightness. There is also visible edge enhancement that cannot be defeated with the sharpness slider. Luckily, color and luminance are fairly accurate. Let’s check out the pertinent graphs.
First up is grayscale tracking. It’s laid out similarly to the graphs we use to measure SDR, only the percent values have been replaced with code values, and there are 16 measurement points. EOTF is the most important aspect of HDR rendering, because luminance is what creates the impression of greater contrast. If the display’s levels don’t match the signal’s, the whole effect collapses. You can see the grayscale stays close to D65 until around code value 500, roughly midway up the brightness scale. At that point, blue begins to clip and a warm tone begins to set in until you get to maximum brightness.
The EOTF chart shows the clip more clearly. It starts to roll off around CV500 and is fully-realized at CV700. What this means is that any signals above 700 will display at the same brightness level. How that affects content depends on how much dynamic range was used during the encoding process. If the S2718D had left its contrast control unlocked, it could be lowered to compensate for this, though bringing out that extra detail would make the picture somewhat flat and murky. The upside is that below the clipping point, it follows the EOTF very closely.
Moving on to color, we ran three sweeps covering Rec.2020, DCI-P3, and Rec.709. Current Ultra HD Blu-ray discs are mastered in the DCI-P3 gamut. The S2718D tracks color saturation well until it hits the limits imposed by its native primaries. This is how an HDR display should look. It manages to nail every target until it simply runs out of color. Though the highest saturations won’t appear, everything below that will be rendered correctly with maximum detail.
When watching HDR content on the S2718D, one should remember that it is still an IPS panel with a native contrast ratio below 1000:1. It won’t suddenly look like an OLED panel in HDR mode. But that judgement must be made while viewing actual content, which is exactly what we did next.
Playing HDR Content On The S2718D
We used the Philips BDP-7501 Ultra HD Blu-ray player to spin a few UHD discs. First off, it’s not quite a plug-and-play experience. You must engage your settings in the right order to make it all work, but it’s simple. After powering up the player, select the S2718D’s Movie HDR picture mode before inserting a disc. This will ensure proper handshake through the signal path to engage HDR10 decoding. In our case, the player’s on-screen messages confirmed we were in HDR mode. If you load the disc before changing picture modes, the player won’t switch the monitor to HDR mode and you’ll need to eject and start again.
To assess the difference in quality, we watched JJ Abrams’ Star Trek and The Martian in both Ultra HD and standard Blu-ray. The S2718D happily accepts Ultra HD signals at full 3840x2160 resolution and down-converts them internally with no apparent artifacts. Watching the same scenes from both standard and UHD discs showed subtle differences in color and dynamic range. The HDR version looks a bit more saturated, and there is clearer detail in both highlight and shadow areas. The dynamic contrast feature doesn’t cause the visible issues we saw during our pattern tests. And the added edge enhancement seems subtle enough not to degrade clarity.
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