Originally Posted by yaomizzle
The St uses the same panel they used on the VT last year (infinite black panel pro I believe)
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You're confusing the filter with the panel. It uses the same filter as the VT30, but the panel is new as chunon said. The UT has no filter, the ST/GT have the infinite black pro filter and the VT has the infinite black ultra filter. All of the panels are new and have the increased brightness and better black levels (among other things).
You can calibrate grayscale on the UT50, but you have to do it in the service menu. The ST50 has them in the user menu, plus it has a gamma slider which is really useful.