As you know, tri means three, as in: tricycle, triple, triad, etc.
A triptych is “a set of three associated artistic, literary, or musical works intended to be appreciated together.” This post will deal with digital images. A triptych can consist of one photo that has been divided into 3 parts visually, or a collage of three photos that are related by theme, colour palette, or design. Triptychs are often used to combine multiple viewpoints of a single subject. Why three? Compositionally it’s more pleasing to the eye to view items grouped in odd numbers such as 1, 3, 5, 7 rather than even numbers, 2, 4, 6. If you wish to know more, Cecilia Walker explains the “Rule of Three and Odd Numbers in Design.”
Here’s a link if you prefer to watch the video in a new tab. I especially like the method he used to add virtual picture frames to the individual images.
How to create a three picture triptych video:
Here’s my example: