32″ 4K monitor with fixed 48/50Hz mode

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Buying a monitor? Please refer to this post before purchasing.


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  • #65360
    hedgepigdaniel

    I recently got burned after buying a BenQ EW3270U because the 24/25/50Hz fixed modes don’t work properly. It’s something that’s quite important to me I can’t easily find information about in in most reviews, so I hope to be able to find a better alternative!

    The use case is that I want to use a monitor for a mixture of programming work and TV/movies. So 60Hz is fine for programming, but where I live (Australia) sport is generally available in 25 or 50fps (and like everywhere else, movies are usually 24fps). Watching a 50fps stream of a football/tennis match on a 60Hz display is absolutely terrible. Every 5th frame is displayed twice and panning motions are extremely juddery. 24fps content isn’t as bad, but still pretty terrible compared to playing it properly at a multiple of 24Hz.

    So I bought the EW3270U because it’s advertised as having fixed 24/25/50Hz modes. And it does, in the sense that they are in the EDID, but the display refresh rate remains at 60Hz. So the only consequence of selecting them is that the monitor does the pulldown. So watching a 50fps stream on the 50Hz fixed mode is still juddery (in fact its worse than the 60Hz mode because the monitor does a far worse job at the pulldown). Looking at it with a slow motion phone camera its easy to see that it just displays every 5th frame twice. It’s especially weird because the monitor supports adaptive sync at 40-60Hz, so clearly the panel is capable at refreshing at 48 or 50Hz, but it doesn’t when selecting any fixed mode. It does the same thing if you overclock it. e.g. if you add a 61Hz mode, all it does is skip every 61st frame. And in case you’re wondering why I don’t use adaptive sync to watch TV and movies – because my computer (a top of the range but non gaming laptop) is not able to drive a display with adaptive sync. Also because software support for adaptive sync is pretty flaky so the most foolproof option is to use a fixed mode.

    With some monitors it’s possible to create custom resolutions/timings for different refresh rates even though out of the box they only support 60Hz. For example my LG 32QK500W is only advertised to work at 60 or 75Hz. But I have added custom resolutions at 50Hz and 72Hz (48Hz didn’t work). So between 50Hz, 60Hz, and 72Hz, I can always select a mode that is a multiple of the content I’m watching. The trouble is it’s very difficult to know if this is possible without actually buying the monitor.

    So – does anyone know of any good and cheap non-TN 32″ 4K monitor which either have fixed modes for film/TV (that actually work) or have the ability to add them?

    And also @PCM2, it would be awesome if you included that kind of information in reviews (whether the refresh rate changes to match all the fixed modes, and what range of refresh rates are supported with custom resolutions)!

    #65362
    PCM2

    Hi hedgepigdaniel,

    To be honest that is a very niche requirement. I’m already beyond saturation point with the amount of detail and small things that need to be tested in reviews. That has increased steadily over the years, so I don’t intend to add to that with something like this.

    That said, I’m curious what you mean by the monitor (EW3270U) still running at 60Hz despite selecting 50Hz or 24Hz etc. If I set this PG32UQX I’m currently using to 24Hz, for example, everything becomes horribly unresponsive (including the mouse cursor). And Test UFO‘s 24fps row looks like I’d expect for 24fps content. The monitor’s ‘refresh counter’ and other indications display 24Hz as you’d expect. What exactly happens on the EW3270U?

    #65372
    hedgepigdaniel

    Ah, fair enough.

    The symptoms are pretty weird. For example for 50Hz, the monitor OSD shows correctly that the input is 3840×[email protected], as does the computer. Despite this, the screen only visibly updates in intervals of 1/60 seconds. So in total it displays the 50 frames the computer sends each second, but it displays every 5th frame for 1/30 seconds and the rest of them for 1/60 seconds (instead of the expected 1/50 seconds each).

    My guess is that internally the monitor has a buffer for the next frame to display, and the frames are buffered at 50Hz, as you would expect according to the mode. But maybe someone forgot to write the code that switches the panel to refresh at 50hz, so the panel keeps reading from the buffer at 60Hz?

    Here’s a video of what it does (this is a slow motion video taken with an android phone camera – the slow motion part is 120fps): https://photos.app.goo.gl/NfmaEVaioXnuFg2B8. You can see the juddering at any speed, but if you play it frame by frame you can see the pattern in the number of phone camera frames per monitor frame. The pattern is 2-2-2-2-4, when instead I would expect something like 2-3-2-3-2.

    #65389
    PCM2

    I’ve discussed this with Mark Rejhon of Blur Busters and we both agree that this “isn’t normal behaviour”. If a monitor has 50Hz listed then it really should work as you’d expect, without the frame skipping you seem to be experiencing. Especially if it is definitely capable of running at such a refresh rate, which you correctly identified it does in this case due to a lower floor of operation for Adaptive-Sync. The BenQ EW3280U has the same refresh rates listed as the EW3270U. And this is a generally advertised for BenQ’s ‘EW’ models so you’d certainly expect it to work correctly. I assume you can observe this frame skipping behaviour using this test as well? Some things to note:

    – You could try power cycling the monitor. Set it to 50Hz, disconnect it from the power but leave it hooked up to the system (and the system on). Wait 30 seconds or more, then connect the monitor power back up.

    – Try this power cycling with the monitor set to 144Hz, then select 50Hz. Mark has observed that setting the monitor to certain lower refresh rates first (such as 24Hz) can trigger odd behaviour at other refresh rates such as 50Hz.

    – This could be a firmware bug, not sure if BenQ could do anything about it but it may be worth contacting BenQ support to see. Mention that you specifically bought the monitor to use it at 50Hz and this was advertised as being supported, but it skips frames as you clearly observe in various tests or just general observation.

    – The monitor may be having an issue with running at this refresh rate with your graphics hardware. A bit of an odd one, but sometimes monitors have certain capabilities that would be reserved for when Adaptive-Sync is available. Even if it isn’t actively being used.

    #66434
    hedgepigdaniel

    Hi,

    Thanks, I appreciate your help 🙂

    I did contact BenQ and with some persuasion they accepted that it was an issue. I got a EW3280U as a replacement (after paying the price difference), which does not have the issue (50fps works fine, with or without adaptive sync).

    As for the cause and whether it will be fixed on newer units of EW3270U, I don’t know. The support person I spoke to apparently contacted the technical team in Taiwan, but I never heard anything else.

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