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Photographs made with artificial lighting (including flash) can be eligible to qualify for the “Guaranteed TCQ” label.
Normal flash and other standard artificial lighting are so commonly used in information reportage that they usually would not warrant a separate “IC” alert by news agencies, in which case TCQ photographers similarly need not provide an alert to viewers.
However, any lighting that produces an effect so unusual that respected international news agencies would make separate note of it in information-reportage contexts must be brought to viewers’ attention with an “IC” alert if the photograph is to be labeled “Guaranteed TCQ.”
After an exposure is recorded, as per def|pen and Q7, apart from the effects of TCQ’s Allowable Changes any alteration, addition, or removal of shadows, reflections, catchlights, redeye, or other flash-induced phenomena disqualifies a photograph from TCQ.
Such photographs cannot qualify for the “Guaranteed TCQ” label.
This disqualification includes lighting effects (like those added instantly by smartphones) that misrepresent the lighting in the scene during the exposure(s).
See also the guide to flash photography.