Poly Studio P21 monitor with DisplayLink driver

owmyeyes

This is an interesting monitor that uses DisplayLink drivers instead of the usual Intel / AMD / Nvidia drivers to transmit data from the computer to the monitor. The cable is connected to a high speed USB-A port on the computer (or USB-C with an adapter, it does NOT need to be display capable). Since this is designed for lower bandwidth than the usual HDMI or Display Port connections, my expectation is that there will be no temporal dithering. The use case is also for Zoom / Team meetings that don't require high image quality so there is no marketing impetus for ONE TRILLION COLORS.

It's currently on sale for only $60 USD so I ordered a couple of them. I will update in a few days after testing.

https://www.bhphotovideo.com/c/product/1677357-REG/polycom_2200_87100_001_studio_p21_21_5_full.html

Here's a related adapter that uses the same technology to connect to two monitors at 4k 60 Hz:

https://eshop.macsales.com/item/OWC/CADPDL2HDMI/#specs

owmyeyes

Update after testing for 24 hours: it works great!

The monitor is extremely comfortable when connected to my laptop (AMD CPU) or my desktop (Intel CPU), both running Windows 11 22H2 with latest updates.

I don't have a way to test for temporal dithering, but I am pretty sure that there is no dithering with the Display Link drivers or the monitor itself. Here's a screen shot of the display properties:

The monitor is also very glossy which is great for me personally - I always get more strain with matte displays. There are some nice bonuses: the built-in webcam, microphone, and speakers are all high quality, and there is even a wireless charger on the base to charge my phone. I highly recommend this Poly Studio 21 monitor to anybody with eyestrain, especially when it's on sale for only $60 now.

photon78s

owmyeyes

I have the same model 4k 60hz OWC displaylink adapter/external graphics card and unfortunately it still exhibits temporal dithering (verified with a high speed phone camera and microscope) when connected to a 8 bit monitor with the bit depth set to 8 bit in windows 11 23H2. Interestingly I don't see temporal dithering when I use a 240hz gaming display.

I am using this monitor which shows dithering with the displaylink:

https://www.sharpnecdisplays.us/products/displays/ea271u-bk

My temporal dithering are similar to those found here:

https://www.youtube.com/@notebookcheckadditionalcon2649

For temporal dithering measurements, I think it makes sense to turn backlight brightness to ensure adequate light for the high speed camera. I use 240 fps and 960 fps slow motion camera modes on the phone.

karthi3219

owmyeyes Hi, how is Poly 21 monitor for extended usage? Is it working good for you even with the bad setup? I am thinking to buy this to use with my Macbook M1. Any suggestions?

jordan

photon78s what gaming display do you use with no dithering ?! Is it comfortable then?

photon78s

jordan

The "gaming display" of lenovo legion 7i laptop (nvidia 4080, gen 8). Screen panel:

https://www.blisscomputers.net/lenovo-legion-pro-7i-16irx8h-2560x1600-240hz-display-ne160qdm-nz3-boe0b8b-screen-36870/

So far at 240 hz setting it is ok, 40-50 % brightness. Still some minor eyestrain but I think that is to be expected. For me at least, it feels better at 240 hz than at 60 hz. Probably from motion smoothness as well. It is suppose to have no flicker for the backlight. Maybe some temporal dithering or other image instability is there but beyond the limits of my measuring.

I also tested pixel inversion on the lagrom test and it seemed decent enough. If I connect a normal 60hz lcd external display, I measure significant dithering from either usb-c or hdmi output with the graphics set to discrete graphics in bios. Ideally, I don't want to rely on high refresh as a band-aid solution. Also, it seems from this forum that using high refresh rate is hit or miss with some preferring standard refresh rates. So many other factors to consider.

owmyeyes

Sorry for the late response. I have used this monitor extensively for the last 10 months (about 40 hours per week).

It's been absolutely awesome - zero eye strain even with my "bad" work laptop.