Product Description TRI-X Pan Professional Films have an ISO speed of 320/26, and feature excellent tone gradation and brilliant highlights. They are especially well suited to low-flare interior lighting or flash illumination. They are also useful for portraiture with low-contrast backlighting outdoors.TRI-X Pan Professional Film (TXP) is available in 120 and 220 sizes on a 3.6-mil acetate base. You can retouch this film on the emulsion or base side.