First, diptychs are not so much made up of great photos, but what the photos say together. Two very dull photos can become one very good diptych. In fact, at least one rather dull photo is often necessary. And conversely, two interesting photos may make a very poor diptych because each image competes against the other.
However, something changes when another image is added. Another not-so-compelling shot, this time of waves lapping on a beach, is placed below it, and a dialog is created between the two. And a far more interesting whole.
The angle problem in the top image is compensated by the downward angle in image below it. And the two comment on each other: they start telling a story.
(It doesn't hurt the diptych to be somewhat color coordinated as well, and display some of the same themes--here: lacy waves and intricate white latticework.)
I think the storytelling part of a diptych is the best part. Here is another diptych that works because it tells a story.
Is the paper bird is looking at the café table, hoping for a crumb?
This image also has another element of a good diptych, movement from one photo to the other. Here the bird is facing the table, the line of the gold construction paper moves toward the curves of the chair almost seamlessly. Your eye moves back and forth from one image to the next. Lines and shapes repeat themselves, making the two seem like one image. The pie-shaped sections on the table repeat themselves in the sections of the gold leaves. In the first diptych, above, the point of the wave moves as if out of the white latticework window above it.
Finally, a diptych can also be a play of two objects or images, placing them together as though they are one object or place. My friend Julia made a diptych like this this week, of a camellia bush and a tree trunk. Here is another diptych of this sort, where the tennis court seems to be placed right under the grassy hill.
This final image could easily serve as a shadow diptych for next week's photo Friday theme, as if the hills themselves are creating the shadow of the trees on the people below.
More of my diptychs can be seen here.