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When the AG346UCD receives an HDR10 signal, it enables two dedicated HDR picture modes. These should not be confused with the three HDR emulation modes available for SDR content. You get Display HDR and HDR 1000 Max. I’ll talk about the differences below.
HDR Brightness and Contrast
I measured the Display HDR and HDR 1000 Max modes and saw no difference in peak brightness. Both top out at 237 nits which is the same value I noted in SDR mode. There is no option for variable brightness which is what OLED monitors use to achieve brighter peak highlights. Black levels and contrast are still unmeasurable, so HDR looks very good but without the verve most other OLEDs have. This is the AG346UCD’s one real weakness. I verified these conclusions by measuring full field and 25% window patterns and got the same result every time.
Grayscale, EOTF and Color
I measured Display HDR and HDR 1000 Max and got very different EOTF curves. The charts above show Display HDR which is the default and best choice. The brighter grayscale steps are a tad warm but nothing that will harm actual content. The EOTF trace runs slightly dark up to the tone-map transition at 70%. Some shadow detail might be hard to see but since the progression is linear, there was no problem in the content I observed. I noted that the 1000 Max mode darkened the picture considerably due to a low luminance curve below the tone-map transition. It also made no difference in peak brightness.
The color chart shows some issues that should be addressed by AOC. Color saturation hits the mark up to around 60% where the points fall short of their targets. The DCI-P3 chart should be fully covered to the 100% perimeter, but it isn’t. Blue comes close but red and green are 10-15% shy. This means the brightest colors will be slightly muted in HDR content. Most material falls in the 40-60% range but the most vivid shades don’t quite render. The AG346UCD is fully capable of this gamut so I can only conclude that this is an unintended result. A firmware update would take care of this issue.
Test Takeaway: OLED monitors need a variable brightness option to render the best possible HDR and the AG346UCD currently lacks this feature. That means its HDR peak is no higher than SDR. I also noted the brightest primary colors were undersaturated. This showed in the tests and in my gaming sessions. The awesome OLED contrast and black levels are there, but color should have a bit more verve.
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