Light is everything in photography, it doesn’t matter whether the source is natural or manmade, to take images for uniqueness understanding the light source is important.
This page is intended to help shed some light on the subject (Pun intended)
Your First Light Setup (in 3 steps) using a speedlight
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Create Professional Studio Portraits using a Speedlight and an Umbrella
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Five different Portraits with one light in a small studio, first shot in each portrait is in TTL to set the exposure than changed to manual