X is for SFX!
SFX is a really cool black and white film that's made in England. It has extended sensitivity on the red end of the spectrum of light...this means you can achieve the effects of infrared photography without going through the hassle of using regular infrared film. Infrared is notorious for the difficulties it presents. From loading the film into the camera (which must be done in total darkness) to figuring exposure (harder than Chinese 'rithmetic), darkness again for unloading the camera and developing the film...making the print...it can be a daunting task. SFX gives the infrared effect without most of that trouble...but...you have to use a very dark red filter on your lens in order to see those effects...the darker the filter, the stronger the effect. IR photos are pretty cool and certainly dramatic...skies are darkened and foliage is rendered as brilliant white...people are too!