What defines clean?
A clean image is one without unwanted clutter. Typically, all image elements have good separation and no distracting tangential intersections.
Standard studio images and mug shots on canvas or paper backgrounds are "clean." They're routinely boring, but they're clean. This isn't what PJs strive to achieve, but it's a good starting point to understand this concept.
Negative perception of clean
Clean backgrounds often have a negative connotation because most studio portraits are made against backdrops. Artists, documentarians and many PJs consider these images inferior and lacking style.
These are simple images. These images only involve a person's face inserted into a generic, solid-colored background. Lighting and focus are important, but anyone with a few minutes training can understand how to make these images in a commercial portrait studio. Otherwise, customers couldn't go to the local superstore for these photos at industry-killing prices.
Amusing the subject and timing shots to subject reactions set images slightly apart from assembly-line portraits. However at the core of these images, they're single-subject nouns.
The primary negative view of clean is a misunderstanding of the purpose of portrait studio photos. I cringe when I go to colorful, exciting events and see some well-intentioned - but misguided - parent line up the family against the most generic background in the place (think wall or side of a vendor's white tent) and make one image.
I understand they're concerned with the subject more than the event, but it still blows my mind. Families make these images because they're compelled to document they were together at a specific place on a specific date (otherwise they wouldn't have a date stamp on Grandpa's face). The generic background negates the purpose of the shot.
I'd hate to see their family slide shows. I can imagine the narrative, "This is our family against a wall at Dizzy World. *click* This is Dad against a tent in the Himalayan mountains. *click* This is Mom against a truck during our African Safari..."
Y'all get the point. The purpose of a studio portrait is to make an image of a person for the sake of having a properly-exposed, focused document of how a person looks at a specific time in specific clothes. If it isn't properly exposed or focused or if the portrait is actually about where it was made without including the environment, the image is a failure.
Why shoot clean?
We've already taken the environmental portrait test, so we won't go to the point-and-shoot extreme. PJs use the existing environment to add context to our images. Additionally, most of our images aren't portraits. We shoot reality in real time in real environments.
We must still isolate the subject enough to allow viewers to understand the image without being distracted by other image elements. Sophisticated images incorporate elaborate layers of information in addition to the main subject; however, the image remains clean and approachable.
How to achieve clean
Because PJs want to tell stories and have viewers understand the story rather than being distracted by background intrusions, we need to know what's in the toolbox to help us achieve this goal.
A large part of getting to "clean" is to think in 2D. Cameras only record height and width. Elements within the image are recorded only in these dimensions. We've already discussed image skeletal structure. The following suggestions should make the underlying structure stronger by eliminating unwanted distractions and clutter.
This is the fastest and most efficient way to create clean images. PJs select available backgrounds without many distractions. However, it doesn't mean the whole background is plain and boring, it means the area around the primary subject is clean. The rest of the image can be a smorgasbord of swirls and tangent lines. We only need one quiet spot in the image to place a essential subject.
Often, there's one wall in a location without too many distracting elements. Otherwise, any other evenly-lit monochrome area will work (a pure blue sky, a distant grove of trees, etc.).
The trick to finding a clean background area in a busy environment is deciding what to eliminate within the frame. In-camera crops are the most efficient way to eliminate distractions. A simple change in the camera angle or position removes unwanted image elements.
Often PJ and/or subject movements help eliminate distracting backgrounds. As both the subject and PJ move, image elements change. Eventually, the elements fall into proper order and the PJ trips the shutter. Then, s/he continues looking for better options.
Movements aren't limited to left and right. These movements can be forward and back to change perspective or align elements differently. The movements can also be vertical to use a ceiling or floor as a background.
Cover distractions with image elements
Let's say there is a big, vicious, black bug on a cream wall during a lecture. We can't have the lecturer move. The bug is already vicious and doesn't need more reasons to mess up our day.
So, we change our camera angle to visually place the speaker's head over the bug. The bug has been eliminated. It's still there, but it's no longer distracting in the image.
With practice, most PJs do this automatically. We see an electrical outlet in the middle of a wall, so we align ourselves to change angle and place the outlet behind the subject. With experience, a minor shift left or right is all PJs need when they actually bring the viewfinder to their eyes.
We've also talked about the dynamic range. From this, we learned anything past three stops (higher or lower) from a light intensity falls off the scale or becomes negligible.
When PJs look at a scene, we try to sort through the light intensities and use the light to our advantage. If the subject is well-lit while aligned in front of a less-well-lit area, we get a dramatic image without a distracting background.
Even if the opposite occurs, we have a properly-lit subject on a white background. It's less dramatic and harder to control, but it's equally clean.
Limited depth of field
PJs transitioning to video need to enjoy this tool while they still have it. When a camera is set on a large aperture (f/2.8 or faster), the depth of field is reduced because the circles of confusion are larger outside the plane of focus. In other words, the background and foreground become out-of-focus and "soft."
Since eyes are drawn to the point of sharpest focus, limiting the depth of field is one of the strongest tools to both grab a viewer's attention and minimize distracting elements.
Again, contrast is a tool to create a strong skeletal structure for an image. By placing light-colored objects on dark backgrounds or vice versa, the PJ accomplishes finding a clean look while improving image structure.
Lens focal length
The focal length of a lens determines acceptable shutter speeds, image compression as well as functional depth of field. As longer focal lengths are chosen, the frame edges close in on the main subject while limiting background elements and throwing them out of focus.
Consequently, the longer the focal length of a lens is, the more likely a PJ is to find (or make) a clean background. Similarly, the shorter the focal length is (often called "wider" for the angle of view), the more difficult it is to control background distractions.
Clean isn't boring
When PJs first attempt to make clean images, they might fall into a trap of single-subject images. While these are clean, they aren't sophisticated. A quality image is clean enough to grab a viewer's attention within two seconds. Then, PJs must provide additional information to keep the viewer engaged with the image.
Often, this involves including additional layers of information. While casual observers still get the information rapidly, those with more time are rewarded for examining the image more thoroughly. This is also what most contest judges seek.
Enough for now,