Light in photography for portraits
By far the most frequent issue with photos is light availability on the central subject. This becomes especially relevant when you want to get your images printed. It may be that you see a beautiful archway or alcove which is surrounded by sunlight. To the human eye as you take in the entire setting, you perceive a beautiful image, brightly lit. Obviously, the perfect photograph. You direct your subjects to stand in the archway, alcove, cave or beneath a tree and take a snap. The problem is that within the area that your subjects are placed there is shade, not light. This means that your friends or family and their faces are in darkness.
Screen versus print
When viewed on screen, your eyes utilise the light available on the digital display to just about make-out your subjects. However, when converted into the print environment for a poster or canvas, the faces are barely discernible. It is much wiser when taking a photo to ensure that your friends or relatives stand within the sunlit area, slightly in front of any shadows. Just take a quick look to make sure their faces are clearly lit. You can still take your perfectly posed image with the archway or tree behind your subjects rather than have them posing in the shadows. Ideally, place your subjects facing the light as it comes from behind you, not them.