WFC3 is a dual channel instrument so light can be directed through either the IR (Infared) or the UVIS (near-UV/visible) channel, though CCD's are used in the UVIS channel only. WFC3 will utilize a 4K x 4K pixel CCD assembly, a simple 2-reflection corrector system, and a filter set incorporating the most popular filters for the ACS and WFPC2. The UVIS channel's entire frame is 1/10th the width of the moon and produces very high resolution pictures of the sky.

Light first enters the instrument through a pick-off mirror, it's then directed into WFC3 and goes through the channel selector and directs the light into with the UVIS or IR channel. After the Channel Selector directs the light into the UVIS channel the light then reflects off 2 mirrors, correcting HST's primary mirror's spherical aberration. The light next goes through a specific filter. After the light goes through the filter wheel, it then goes through a series of UVIS Detector Windows. After this the information then gets captured into the CCD for processing.