The placement of the reflector should be determined by the position of the key light at the scene. A common technique is to position the key light and the reflector on opposite sides of the shooting axis (the line connecting the camera and the subject). However, there are exceptions. For instance, if the key light is coming from the left-acting as a side-backlight or near-backlight-but the background is dark on the left and bright on the right, the reflector might be placed on the left side of the axis.
Angle
The angle (height) at which the reflector is positioned is a crucial factor directly affecting the facial contours, depth, and overall visual impression of the subject. It is generally understood that a high light position creates heavier shadows on the face, making the subject appear leaner, whereas a low light position produces lighter shadows, making the subject look slightly fuller. However, these are merely general guidelines, as every person's facial structure is unique. Some round faces still possess distinct angular features, while some slender faces have full contours. For example, a woman with an oval face will look good regardless of whether a high or low light position is used.
At the same time, simply choosing the reflector's position is not enough; the choice of camera angle or the subject's pose is equally important. Since that falls outside the scope of this post, I will not elaborate on it further.
Intensity
This refers to the brightness of the light reflected onto the subject. Some might ask, "The reflector just reflects light as it is; you can't adjust its output power, can you?" Reflected light is brightest in the center and gradually dims toward the edges, though the transition is relatively smooth. If you have a reflector, simply aim it at an object on a sunny day to clearly observe this effect. However, the area where the brightness tapers off is much smaller than the central area of uniform brightness. (With very small reflectors, this effect may be harder to perceive; since the central bright zone is already small and the transition zone is also narrow, the transition area on a small reflector becomes minuscule.)
The tapering brightness zone is the part of the reflector most frequently utilized. By making use of this area, you can achieve the exact level of illumination you desire. We have all seen plenty of photos where the use of a reflector went wrong-many people here have posted such examples. The most common mistake is simply bouncing all the reflected light directly onto the model's face without nuance. The result is often either an overexposed face or an underexposed background (though this might not happen if the background is already quite bright), not to mention making it hard for the model to keep her eyes open. Such careless use of a reflector is ill-advised. Of course, using a reflector correctly and effectively is actually quite difficult. Using a reflector for fill light is essentially adding another light source to the subject-the principle is the same as using a flash or studio modeling lights. However, while the output of artificial lights can be precisely controlled, reflectors are much harder to manage. You can't simply tell a reflector to reduce its output by one stop, nor can you easily instruct the person holding it to do so. Even if you use a light meter to set a specific lighting ratio-say, 1:2-the slightest movement of the holder's hand can shift that ratio to 1:3 or 1:1.5.
Only true masters of the reflector-such as veteran lighting technicians in film studios-can achieve this level of precision. With just a glance at your chosen background, the model's pose, and your focal length, they know roughly where to position the reflector; when they lift it, the result is almost spot-on. You might only need minor tweaks-"angle it away a bit more" or "bring it in a little closer." Even if they lower the reflector while you direct the model and then raise it again for the actual shot, the lighting effect remains essentially what you had previously adjusted. That is the mark of a true professional.
For the average photographer, however, it is rare to have such an expert on hand to manage the reflector. Consequently, controlling the reflected light becomes the biggest challenge when using a reflector for fill light. Ultimately, it comes down to using the reflector to control the lighting ratio-a complex subject that cannot be fully explained in just a few sentences here. Mastering it relies on personal experience, intuition, and the ability to assess the model's specific features. Improving one's experience and judgment in this area requires constant practice-using actual film and relying on personal intuition-or the guidance of a mentor or teacher.
Surface Area
This aspect involves two factors: The area of light reflected onto the subject and the size of the catchlight formed in the eyes. The illuminated area on the subject is actually related to the "tilt" direction mentioned in the section on "Intensity." Generally, for a half-length portrait, if there are no foreground or background elements, tilting the reflector to the side is a good option; this prevents the illuminated area from becoming too large, which could otherwise cause other parts of the frame to become overly bright and distract from the face. However, if foreground or background elements are present, tilting the reflector upward is preferable. A common mistake to avoid is having a relatively large catchlight in the pupil when the background is dark and the face lacks distinct highlights; such a catchlight appears unnatural and illogical, failing to align with realistic visual perception. In environments with relatively even ambient lighting, catchlights are typically small. Since frontal fill light is usually provided by a flash-which acts as a point light source-it rarely produces a large catchlight.
Quantity
If circumstances allow, it is best to use two or more reflectors. One provides fill light from the standard height, while the other is positioned at a lower angle-and perhaps closer to the subject-to soften facial shadows and add a second catchlight in the eyes, creating a more natural look in certain settings. If resources permit, a third reflector can be used to create a rim light (or outline light) on the subject, adding a sense of three-dimensionality to the image. If we were to rank these reflector-use factors from most difficult to easiest to master, the order would be: Intensity → Angle → Surface Area → Height → Quantity.
