FinePix IS Pro filters are required to photograph in IR or UV wavelengths. Infrared filters are readily available at low cost from many sources, but ultraviolet filters – and suitable lenses – can be expensive. Photography in infrared and ultraviolet poses its own special challenges regarding exposure and – above all – focusing a SLR camera. By definition, these forms of light are invisible to the human eye. The IS Pro includes a Live View mode that relays what the sensor sees as live video to the LCD screen (and, optionally, via USB to a computer running appropriate software). Some lenses have separate
Invisible ink purpose stylus, stamp, fountain pen, toothpick, calligraphy pen, or even a finger dipped in the liquid. Once dry, the written surface looks as if it were blank, with a similar texture and reflectivity as the surrounding surface. The ink can be later made visible by different methods according to the type of invisible ink used. The ink may be revealed by heat or by application of an appropriate chemical, or it may be made visible by viewing under ultraviolet light. Inks which are developed by a chemical reaction may depend on an acid-base reaction (like litmus paper), reactions similar to