Image quality analysis of the UVIS channel during ground testing show 90-92% of the flux from a 250nm point source falling within a diameter of 0.35 arcsec. This decreases with increasing source wavelength, to 85-86% for a 810nm point source.
UVIS Flight Detector
ISR 2005-10: WFC3 UVIS PSF Evaluation in Thermal-Vacuum Test #1
G. Harting 03 Mar 2005
ISR 2004-08: Preliminary WFC3 UVIS PSF Evaluation
G. Hartig 24 May 2004