Have you tried a right click on the vegas.exe file -> Properties -> check "Override high DPI scaling behavior. Scaling performed by: Application"?

Currently Vegas is using the default Windows 10 scaling feature in which windows will scale the application so that it is displayed well in based on your display settings. This was also the case in Vegas 14. We used this setting as a way of resolving the sizing issues that many people were seeing with Vegas 13, but the scaling will result in a somewhat "fuzzy" (as aboammar stated, it very much like Full HD scaled to 4k, because that is what Windows is actually doing to it). This is how many older applications handle high dpi situations now.

As we continue to revamp the interface, over time we will be adding more high DPI support into the application. Currently, you can turn off the automatic scaling as OldSmoke suggested. This will likely result in some display issues (placement and sizing of things), and the button icons will still be "fuzzy" as we do not have a mechanism in place currently for using higher resolution graphics for these. But...doing this will result in sharper text and a sharper preview image. Watch for high-dpi improvements in future updates.

Currently Vegas is using the default Windows 10 scaling feature in which windows will scale the application so that it is displayed well in based on your display settings. This was also the case in Vegas 14. We used this setting as a way of resolving the sizing issues that many people were seeing with Vegas 13, but the scaling will result in a somewhat "fuzzy" (as aboammar stated, it very much like Full HD scaled to 4k, because that is what Windows is actually doing to it). This is how many older applications handle high dpi situations now.

As we continue to revamp the interface, over time we will be adding more high DPI support into the application. Currently, you can turn off the automatic scaling as OldSmoke suggested. This will likely result in some display issues (placement and sizing of things), and the button icons will still be "fuzzy" as we do not have a mechanism in place currently for using higher resolution graphics for these. But...doing this will result in sharper text and a sharper preview image. Watch for high-dpi improvements in future updates.

On my 2560x1440 27" monitor scaled to 125%, the icons and text are crisp. But yes, some text is misplaced but nothing that would stop me from using it.

At 125%, things shouldn't be too bad. I've noticed quite a few issues at 150% and beyond.

At 125%, things shouldn't be too bad. I've noticed quite a few issues at 150% and beyond.

Indeed, I scale my ultra wide (which is not 4K, but close due to the aspect ratio) at 125%

I think someone mentioned experimenting and finding a boundary condition at 149%. So 149 = not fuzzy, 150 = fuzzy. Try it? ( I don't have a 4k monitor, but would like to get one.)

Have you tried a right click on the vegas.exe file -> Properties -> check "Override high DPI scaling behavior. Scaling performed by: Application"?

Yes I tried that and it messed up the interface, though texts do appear very sharp, 4K sharp.

Currently Vegas is using the default Windows 10 scaling feature in which windows will scale the application so that it is displayed well in based on your display settings. This was also the case in Vegas 14. We used this setting as a way of resolving the sizing issues that many people were seeing with Vegas 13, but the scaling will result in a somewhat "fuzzy" (as aboammar stated, it very much like Full HD scaled to 4k, because that is what Windows is actually doing to it). This is how many older applications handle high dpi situations now.

As we continue to revamp the interface, over time we will be adding more high DPI support into the application. Currently, you can turn off the automatic scaling as OldSmoke suggested. This will likely result in some display issues (placement and sizing of things), and the button icons will still be "fuzzy" as we do not have a mechanism in place currently for using higher resolution graphics for these. But...doing this will result in sharper text and a sharper preview image. Watch for high-dpi improvements in future updates.

Thanks for your detailed reply.

So, I understand from you that Vegas Pro 15 "still" dose not fully support or take full advantage of 4K resolution.

I tried all Windows 10 scaling options, and this is what I got:

1- Default System Scaling: Texts, icons, and graphics elements appears fuzzy. (Screenshot 1 and 2)

2- Override High DPI (Application): Some elements in the GUI is messed up. Texts are true 4K sharp, but icons, and some graphics elements appears fuzzy or messed up. (Screenshot 3 and 4)

3- Override High DPI (System Enhanced): Overall GUI is too messed up .. not usable. (Screenshot 5)

In my opinion, the default system scaling is the most usable even though texts, icons, and graphics elements appears fuzzy, but at least the scaling is correct.

So I guess I will have to live with that until Vegas Pro 16 fully support high DPI, just like BMD Resolve do.