There is no photograph here to determine what the main pillar is. Sorry. But, for those who don’t know, let’s give a little lesson what the main pillar of a photograph is. The main pillar is actually not a thing. It’s three pillars, and they’re basically principles of photography - like principles of design. Every picture has some degree of these three elements: aperture, shutter speed, and ISO. Aperture is how much light is being exposed on the film.
Shutter speed is how quickly the shutter closes to create that snapshot. ISO is the hardest one to understand, but it’s basically how much light is needed to take a picture on a certain camera. All three of these things can be changed, and can create different kinds of pictures.