WikiAnswers makes it sound easy: A diptych is a photograph that uses two different or identical images side by side to form one single artistic statement. The two images can literally be in contact with each other, or separated by a border or frame.
The human body is - in most cases anyway - aligned vertically with the head on top and the rest below. It is often a problem to include the face and, for added information, hands in the frame. Usually we position the face or eyes in the upper golden section. But how to include the hands? If we want to get close to our model, it is challenging to include them, and the question remains how to connect composition-wise the space between hands and face. Avoiding a too low, and therefore sometimes cropped position of the arms is also challenging like it was in this image.
One day I found the two images below on Nicoleta's lovely blog, and seeing them together sparked the idea of putting them into the same frame.
As a result, we have an image that works two ways: we have a portrait above and a documentary image below. The scene could have been put into a single frame, but making it two and including them in a split single frame results in more details due to the closer point of view. In a single frame, we couldn't get close to the subject like this. At this moment, it came to my mind that I'd made a similar experience with two of my own images.
Of course if we compose the split afterwards, it can't be as good as a pre-visualised and accordingly executed concept. The following examples are works from a joint project by Ara Oshagan and Levon Parian (who is a visual artist, not writer). In these images, it becomes obvious how important it is to fine-tune the composition of the two separate shots to make them work as a whole.
The upper part of the image below has a dynamic composition with the head tilted to the left side (creating a downwards "negative" diagonal). It is perfectly balanced out by composing the lower part equally dynamic, with a diagonal from the lower left to the upper right. The hands make the music, so to say, and the direction of the model's limb makes the rest by serving as both background and compositional element to balance out the alignment of the upper part.
The image below is, on the contrary to the first, composed following a vertical line. Both parts follow the same conceptual symmetry: any diverging lines of composition would ruin the impression. The face is slightly out of this vertical, though, but only to the extent of adding a little tension to the vertical composition.
As I said, the two images are part of a photo-essay on survivors of the Armenian Genocide, Ara's joint project with Levon Parian. Check it out by any means, and watch the video in my previous post for a better understanding of what these people went through.
And the variations are endless. Environmental portraits or glam shots (and virtually everything) can be spiced up with this method, just have a look at Carrie Yury's works.
And if we think about all the possibilities offered by diptychs, a triptych could be almost a visual overkill. Sometimes it seems to me that hunting high and low for new editing techniques is all but a one-way street. Going back to the basic techniques of visual arts can be a much more inspiring and therefore rewarding experience.