The discussion in the previous section only considered how to maximise the signal to noise ratio per resolution element. For certain types of experiment, it may also be important to note that the detectors offer different choices of format and pixel size. For spectroscopic observations, the WHT IPCS provides 2560 pixels along the dispersion direction, each about 10.5 microns in size. The TEK CCD provides 1024 pixels along the dispersion direction, each 24 microns in size. At present the IPCS does offer smaller pixel sizes than any of our CCDS, and is the only detector capable of realising the full resolution potential of UES. We anticipate that smaller-pixel CCDS (15 micron) will be installed by the end of 1995..