12. Depth.

When in real life objects could be two or three-dimensional in shape, in a picture a shape always is two-dimensional. and only the tonal changes throughout your picture-object can allow for the impression of depth. The photo of the marsh taken at the Bush Gardens in Florida was taken on Kodachrome film using Minolta x-700 camera at 1/120 shutter speed and a 70-210 zoom lens set at f.5.6.

Some photographs look two-dimensional lacking diversity of the tonal ranges, while the others, conversely, have a strong presence of many tonal ranges of the objects and/or possess three planes -- foreground, middleground and the background, which bring out depth of what, otherwise, would have been a much flatter appearing collection of the picture elements.

Thus a lack or possession of a broad range of tones across your picture's objects, in itself is often responsible for the absence or presence of compositional depth in any photo.