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Did you try to change the HDMI version yet?
Yes I try it to change from 1.4 to 2.0. but it is the same (cropped display).
Have you tried updating lenovo video drivers from intel, nvidia or amd websites?
I check drivers update on official Lenovo site and there is no new drivers updates.
What happens if you turn off laptop screen?
I would try to update the drivers from here: https://www.intel.com/content/www/us/en/support/intel-driver-support-assistant.html and https://www.nvidia.com.br/Download/index.aspx?lang=br
I update the drivers but everything is the same. What I managed is to get normal display on Acer XD1520i projector on extended desktop and resolution 1900x1200 (on Acer projector properties) . When I go back on Duplicate display, again Acer project cropped display.
>>>normal display on Acer XD1520i projector on extended desktop and resolution 1900x1200 (on Acer projector properties>>>When I go back on Duplicate display, again Acer project cropped display.>>>
This further confirms nothing's wrong with the projector. You will just have to experiment with the Lenovo's graphics HDMI output resolutions settings.
Are you getting any assistance or responses from the Lenovo users forums? I don't have a ThinkPad 15 to help guide you on this. All I can say is that the projector seems to be OK. The projector is s only displaying what the Lenovo HDMI output port is feeding the projector's HDMI input port.