Reverse Engineering Lighting

OK, I'm back at it. I don't know about you, but when an image catches my eye, I almost always analyze it. I look for clues about lighting, lens settings, post-processing adjustments, etc. In the next few posts I'll describe what I look at to deconstruct lighting. In tomorrow's post we'll use a series of full-body images to illustrate how different lighting sources render shadows.

A Few Common Reflection Workarounds

Full-length Shots on White

Creating full-length shots on pure white can be problematic. It can be difficult to keep the floor as bright as the vertical portion of the backdrop unless you "wash" the floor with additional lighting either from below or above. This is not always a viable solution. A very effective workaround is to place a smooth, highly reflective sheet below the subject. The floor then acts as a mirror in which the lighted background is reflected. Direct reflection saves the day.

Eyeglasses

Portrait photographers often have to grapple with reflections in eyeglasses. Assuming that you are using a typical portrait-lighting setup with main/fill sources somewhat above face level, you typically have three options: raising the eyeglass arms, raising the offending light source, or repositioning the subject. Raising the eyeglass arms slightly at the ear will cause the eyeglass lenses to tilt downward. A small adjustment may be all you will need, and most viewers will not detect that the earpieces have been raised. Alternately, you may choose to raise your main or fill light sources until the reflection disappears. If adjusting the glasses or moving the lighting fails to solve the problem, consider repositioning the subject. For instance, using broad lighting with a 2/3 facial view, as shown in the image below, the main-light reflection will be directed away from camera view.



On-site Speculars

If you've shot a lot of on-site images with on-camera flash, you've undoubtedly encountered the "ugly blob of light." Reflective surfaces, especially those nearly parallel to the sensor plane can kick back an extremely bright and ugly direct reflection of your flash. To avoid this common problem, you may need to shoot from a different angle or temporarily remove certain reflective objects from the scene. Scan the shooting area for mirrors, reflective clock faces, pictures with and without protective glass, and sundry other reflective items. If you are shooting table shots at a wedding reception, for instance, position yourself so that you are not square to mirrored walls, windows, or glass doors behind the subjects. If you are doing shots in the home, be on the lookout for framed pictures and mirrors. If you are shooting in a business, note the positions of the computer monitors and personal items such as framed pictures and reposition things as needed.

I'm not sure what I'll tackle next, but suggestions are always welcome.

Ideas Anyone?

I'll be putting together another short blog post early this coming week that will cover just a few more uses/consequences of direct reflection. That will wrap up the subject of reflection for now. I'm not quite sure what I'll tackle next, so I'm putting out a call to anyone who has ideas for good subject matter. Please leave any ideas in the comments below or email me at Barry@portraitlighting.net. I will check this particular post periodically to see if any new ideas have come in.

Reflection Part 6 (Darker Skin Tones)

If you've attended a few seminars on lighting or portraiture, you've likely heard an audience member ask about exposure for people with dark skin. Invariably, the speaker announces that exposure is exposure and there is no need for compensation. The argument is often supported by an example consisting of an image of several people of differing skin tone. If the exposure is biased for the skin of any one person, an unfavorable skin rendition will result for the others. The argument is irrefutable, but for the inquirer, the answer is often unsatisfying. They want more detail in the photographic rendition of dark skin, something closer to what they see with the naked eye. And, they're not alone. Shortly before digital capture overtook film as the medium of choice, Kodak was marketing a special portrait film for deep-complected skin. If Kodak thought this was an issue, maybe there is something to it.

Dark vs. Light

The subject of skin tone is a very interesting one. It can be approached from both a technical and social angle. In my conversations with people from around the world, I have been surprised by how often darker skin is associated with lower social standing. No doubt, some of this bias is a vestige of Western hegemony. While it would be foolish to assume that a dark-skinned customer will want a lighter rendition of their skin, it can sometimes be an issue. I'm not qualified to talk about the social aspect, so I'll take a stab at the technical.

Diffuse vs. Direct Reflection

In general, the darker the skin, the more it absorbs light and the less it reflects it diffusely. Direct (specular) reflection, however, is dependent primarily on the sheen of the skin surface, and not tone. So, while light and dark skin may produce very similar levels of specular reflection, there will be a big difference in the diffuse reflection. As a result, direct reflections make up a greater proportion of the light reflected from dark-toned skin and the implications of this are many.


Defining Form with Shadow and Highlight

On light skin, the specular highlights ride on top of the glowing skin (diffuse highlight). These specular patches may enhance form, but that are not usually the primary feature that defines form and depth. On light skin, it is the difference in the areas of diffuse highlight and the surrounding shadows that give the face form. With extremely dark skin, shadows and diffuse highlights may be so dark that distinguishing between them becomes difficult. At this extreme, form is rendered by the differences between the specular highlights and the surrounding areas, both shadow and diffuse highlight. Simply, or perhaps over-simply put, with light skin you create form and depth with shadows. With dark skin, you do so with highlights.

Some Celebrities

If you are not quite getting the picture, take a look at some real-world renditions of people with very deep and very fair complexions. One of the best examples of dark African beauty comes in the form of model Alek Wek. A much photographed model, you'll find plenty of images of her on the web. Notice how areas of specular reflection on her cheeks, forehead, nose, and chin often define the form of her face. At the other extreme, take a model with fair skin. Nicole Kidman or Taylor Swift are two examples. Notice how form on these faces is created by shadows around the cheeks, nose, brow, and jaw.

Lighting Strategies for Dark Skin

There is no one right way to light a face, but here are some things you might want to keep in mind when planning your lighting for dark skin. Specular highlights are inevitably more prominent for darker skin. Controlling them is key to achieving the desired result. You'll probably be leaning one of two ways to control specular highlights: minimizing them or making them as large and prominent as possible.

Minimizing specular highlights is not always easy. One approach is to place your lighting, preferably smaller or controllable lights, at oblique angles so that much of the direct reflection is aimed away from camera view. Feathering is another technique that can help, as feathering can decrease both the apparent size and intensity of the source's specular reflection. These techniques were used in the second example from the prior post. By reducing specular reflection, you let the diffuse reflection do more of the talking, and increase tonal richness in the process.

The other approach is to define form by painting the face with large and soft specular highlights. By using very large light sources, you create large specular highlights that can cover the greater part of many facial features. As the light source is large, the energy of the specular highlight will be distributed over a large area, resulting in a pleasant glow. The following picture, as corny as it is, demonstrates the approach. The main light for this image was a large 3' X 4' softbox placed in close.

Reflections Part 5 (Another Example)

Above is the image from the previous post, but without the circled highlights and with an inset image that uses the same lighting but with the subject positioned for short lighting. What is most notable about these images is that they employ a very common lighting setup, with the main light positioned about 45 degrees off of the camera-subject axis and somewhat above the face. You'll find some variation of this type of lighting in many high-volume portrait studios around the world. Fill lighting of some form is usually combined with the main light to control shadow detail. While the character of the highlights will vary from one implementation to another, the positions will remain largely the same. You can expect to have a highlight on the forehead, the tip of the nose, on one or both cheeks, and, depending on facial structure, a few other spots. You can create hard, distinct highlights by using small sources pointed squarely at the subject, or much softer areas of glow when using very large sources in combination with appropriate makeup. In an upcoming post, we'll look further into how to control these highlights. For now, we'll leave the ubiquitous and take a look at something completely different.



Taking Advantage of Direct Reflection


The above image was created with an unconventional lighting consisting of a large Fresnel light immediately in front of and above the subject. That light was pointed almost straight downward, and feathered ever so slightly back toward the camera, resulting in a beam of light that just grazed the front of the face. A silver reflector was placed just in front of the subject and slightly below his hands. Additionally, kicker (accent) lights were placed behind the subject at approximately + and - 150 degrees off the camera-subject axis.

Minimizing Direct Reflection

This image helps demonstrate some interesting properties of direct reflection. First, the direct reflections of the business portrait are gone, replaced here by a line of specular reflection along the bridge of the nose, and a distinctive highlight on the lip. The near absence of specular highlights occurred because the direct reflections of the Fresnel source were projected downward off the face and not back toward the lens. Only the aforementioned nose and lip highlights can be seen by the lens. The reflector acted similarly, projecting light obliquely up across the face. The result is just a hint of glow across the face. Here, the goal was to minimize visible direct reflections on the face, but the kicker lights performed in quite the opposite manner.

Maximizing Direct Reflection

Unlike the frontal lighting, where direct reflections were mostly directed away from the view of the lens, the kicker lights were positioned to take full advantage of direct reflection. The specular highlights along the sides of the head are largely direct reflections of the kicker lights, and, as direct reflection is more "efficient" than diffuse reflection, these highlights are quite bright. In fact, the main light metered more than one stop brighter than the kickers, yet the lighting along the sides of the head appears brighter. Keep this in mind when placing accent lights. They can look brighter than you expect.

Next Post

In the next post we'll look at lighting darker skin tones.

Reflections Part 4 (Real-World Examples)

Finally, we're ready to take a look at some real-world portraits and examine reflection at work. Before jumping to today's portrait, I'd like reiterate a few things. First, skin will reflect light in both a diffuse and specular manner. The amount of diffuse skin reflection depends largely on skin tone, with darker skin reflecting less. The amount of direct reflection depends on the skin's surface sheen, and will be strongly influenced by the position and size of the source.



Above we have a rather typical business portrait in which areas of specular (direct) reflection have been circled. These shiny patches are actually reflections of the light source (direct reflections) superimposed on areas of diffuse reflection. If you look carefully, you can often make out the shape of the light source in such reflections. No place are they more distinct than in the direct reflections in the eyes (aka catchlights). Clearly, these specular patches vary in size. Notice that surfaces that curve gradually, the forehead for instance, will have larger, and generally less intense, highlights. Smaller areas with a very distinct curvature, such as the bulb of the nose, will have smaller and more intense areas of reflection. The position and size of reflections will vary depending of the size and position of your light sources. The circled areas in today's portrait are all reflections of the main light, but any light, including a fill light, can create specular highlights.

In the next post, we'll look at an unconventional portrait that digs deeper into the properties of reflection. In the meantime, if today's material was new for you, take a look at your pictures and those of other photographers and examine the highlights. You can learn a lot about how an image was created by doing so.

Reflections Part 3

Today I will be adding a bit more about diffuse reflection, but before I get started, I think it would be wise to backtrack a bit.

Reflection, Absorption, and Transmission

Reflection is just one phenomenon that light can experience when it encounters a boundary (surface) traveling from one medium into another. When light hits a boundary, it may also be transmitted through the new medium or absorbed by it. For the purposes of our discussion, these three phenomena (reflection, absorption, & transmission) account for all of what light can do when it leaves one medium and encounters another. What is not absorbed or transmitted is reflected. The degree to which light is absorbed, transmitted, or reflected will depend on both the substance and the nature of the surface boundary. For example, clear glass will transmit a large portion of the light that hits it, and absorb relatively little. It can be an efficient direct reflector, but a poor diffuse reflector. If the surface of that glass is etched to produce a frosted surface, it will reflect much more light in a diffuse manner and not nearly as much directly. Unlike glass, black soot will be poor light transmitter, but a very good absorber. As it absorbs much of the light, it will be a relatively poor reflector. I think you get the idea.

Diffuse Reflection

Diffuse reflection was described in the first post on reflection. If you didn't read that, you may want to jump back two posts. An ideal diffuse reflector reflects light in an omnidirectional way. As a result, the surface will appear the same to the viewer regardless of the angle at which the light approaches the surface and from which it is viewed. Surfaces that reflect in a primarily diffuse manner are usually dull in appearance, but this doesn't have to be the case. For instance, a surface covered in fine crystals or glass beads could be both brilliant and reflect largely in a diffuse way.

We are surrounded by diffuse reflection. Our perception of form, luminance, and color are largely a function of how we see diffuse reflection. Foliage, sidewalks, clothing, and painted structures reflect the vast majority of light in a diffuse manner. Light meters are calibrated under the assumption that the metered scene will consist largely of diffusely-reflecting objects, and that, on average, the scene will reflect about 18% of the light that hits it. This leads us to the next topic.

Reflectance

Reflectance is a measure of the percentage of light that is reflected relative to the amount that is incident on the surface. All other things equal, a lighter-toned surface will have a higher reflectance than a darker one. Darker surfaces generally absorb a greater portion of the incident light, leaving less light to bounce back. I'll explore reflectance in more detail, especially as it relates to balancing the specular and diffuse reflections on a face. The following posts will be more fun, with real-world examples showing applications of the boring stuff of the past three posts.