It’s a very difficult question to answer, but let’s look at a few major things a cinematographer considers each time they set up their camera.
TV sets and other moving-image devices, especially if they are non-HDR, cannot display as wide a dynamic range as most scenes have in real life. So it is often seen as desirable to make the most of what contrast a screen can reproduce by including at least one area of the blackest black and one of the whitest white, with a good distribution of all the tones in between.
Contrast makes an image richer and also easier for the viewer’s brain to interpret, but as with all of these rules, it is perfectly possible to break it with excellent results. For example, you may want to keep a scene in a prison entirely in the shadows, so that when the prisoner escapes into the daylight the viewer will feel the impact of the highlights. Tonal distribution has a big impact on mood, and thought should be given to what mood a DP wants to convey.
Since Isaac Newton invented the colour wheel in 1704, artists have devised several colour schemes which can evoke different feelings, the most common in cinematography being complementary and analogous.
A complementary colour scheme uses two hues on opposite sides of the wheel for maximum colour contrast, punch and vibrancy. Think Ripley’s yellow power loader against the blue lighting of Aliens, or the infamous teal-and-orange grading of Michael Bay’s films.
An analogous colour scheme uses hues adjacent to each other on the wheel for a harmonious or oppressive effect. Think the greens of The Matrix, or the reds of Mars in Paul Verhoeven’s Total Recall.
There’s more on colour schemes in this post.
“The so-called rules of photographic composition are, in my opinion, invalid, irrelevant and immaterial,” said the great American photographer Ansel Adams. I might not go that far, but they can certainly be overrated.
The Rule of Thirds, for example, is intended to produce a balanced image, but what if you don’t want a balanced image? Placing a character in an unusual part of the frame, as is frequently done in Amazon’s Mr. Robot, can be powerfully unsettling and say much about the character’s status and mindset. Breaking rules for the sake of breaking rules may not be wise, but breaking them in a single shot to make the viewer sit up and take notice, or breaking them subtly but consistently throughout a film to subconsciously cue the audience into a theme or character trait, is a good use of cinematic technique.
As for camera moves, some believe that they should always be motivated. Some like them to be expressive. Some simply like to keep dollying the camera back and forth to add energy to a scene. As long as the movement helps to immerse rather than distract the viewer, it is serving its purpose.
As film and TV are usually monoscopic media, cinematographers often aim to compensate by enhancing other types of depth cues. Commonly this is through lighting – using backlight to cut a layer out from the background, using colour to separate layers, or alternating light and dark layers. Haze and camera movement can also be used to create a greater sense of depth, as can lens choice, be it a wide lens which exaggerates perspective, or a long lens that throws backgrounds out of focus.
The result is not just impact but clarity, ensuring the viewer is not distracted from the story trying to figure out what they’re seeing. Again though, you may sometimes want just the opposite, to disorientate the viewer or make them work to find the important element in the frame.
This post has some good examples of depth cues.
A DP has the responsibility of capturing on film or digital media the work of every other department on the production (except sound!). If the costumers have spent weeks sewing beads onto a period dress, a cross-light to bring out the texture is the least the DP can do. If the make-up department are struggling to hide the joins in a prosthetic, softening or dimming the lighting will help. If a huge set has been built or an expensive location hired, showing it off in at least one wide shot is probably advisable.
Story and Character
As I’ve hinted throughout, the most important thing is that every aspect of the shot is working towards telling the story, revealing or enhancing character, and conveying the right overall mood. This might be by keeping everything quiet and conventional to let the performances shine through, or it might be through crazy framing, crunchy contrast and dramatic movements. The possibilities are endless.