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A POTD is an acronym for "Photo of the Day", "Picture of the Day", "Post of the Day" or "Poll of the Day". It is a term most commonly used by online digital photography communities as an honor to outstanding photos that are selected daily from among that community's membership. They can either be tagged as POTD or displayed in a special page on that site...

In infrared photography, the film or image sensor used is sensitive to infrared light. The part of the spectrum used is referred to as near-infrared to distinguish it from far-infrared, which is the domain of thermal imaging. Wavelengths used for photography range from about 700 nm to about 900 nm. Usually an "infrared filter" is used; this lets infrared (IR) light pass through to the camera, but blocks all or most of the visible light spectrum (the filter thus looks black or deep red)...