Reflections Part 2

In the previous post on reflections we covered the basic characteristics of direct (specular) and diffuse reflections. In this post I'd like to address three characteristics of direct reflections: direction, size, and intensity.

DIRECTION

Direct reflections have a very definite sense of direction. In fact, on a plane reflective surface, the angle at which the light approaches the surface is exactly the same as the angle at which it leaves. This principle is most often stated as: the angle of incidence equals the angle of reflection. It can be extended to non-planar reflective surfaces using the tangent to the surface at the point of reflection. All of this is shown in the diagram below. This principle is very important and explains, among other things, why a light's placement can have a big impact on its apparent strength.



SIZE

The size of the reflection will vary based on the curvature of the reflective surface. Compared to a reflection on a plane surface, convex surfaces will yield a smaller reflection and concave surfaces a larger one. For convex surfaces, such as spheres, a smaller radius of curvature will yield a smaller reflection. This is shown in the diagram below, where the grayed areas represent the reflection. The implications of this principle are numerous, and it explains why, for instance, a specular highlight on one's nose is much smaller than the one on the forehead.



INTENSITY

The intensity of a reflection depends not only on the intensity of the source, but the size of the reflection. For instance, in the diagram above, the smaller reflection on the smaller sphere will be brighter than the reflection on the larger sphere. That is because both must reflect the same amount of energy, but must do so over differing surface areas. And, this explains why the that small specular highlight on the nose is brighter than corresponding hot spots on the cheeks or the forehead.

The next post will be a quick one on diffuse reflection, and then I'll try to bring it all together by applying these principles to real-world applications and examples.

Reflections Part 1

First, I apologize again to anyone who was looking for new content here. I made a promise I couldn't keep, and I'll not do that again. Nevertheless, I will try to add new content as time permits.

Today I'd like to start the first of several posts on light reflection. For me, it is the most important of all lighting concepts. I'll try to keep the technical stuff to a minimum, using visual aids to make the major points.

Reflections come in basically two forms: direct and diffuse. A direct reflection is a reflection of the light source, and is also called a specular reflection. Mirrored surfaces, for example, produce primarily direct reflections. A diffuse reflection, also known as an indirect reflection, is created when light striking a surface is scattered in a variety of directions. Matte paper, and talcum powder are two examples of diffuse reflectors. Keep in mind that no surface is a perfect direct or diffuse reflector, rather most surfaces produce a combination of both direct and indirect reflection. The differences between the two reflection types are shown diagrammatically below.





The diagram above shows the setup for a little experiment which uses a highly polished steel sheet as a direct reflector and a piece of white foam-core board as a diffuse reflector. The series of photos below shows the results for the two surfaces and two lighting positions. Note that the white board reflects back light similarly regardless of light position, while the polished plate produces strikingly different results. The direct reflector here acts in a kind of on-or-off fashion, either you see a reflection or you don't.









In the following posts, we'll dig a bit deeper into reflections and examine how they can affect our portraiture.

Nine Months, a Great Time

Happy New Year to all! I'm committed to regular posting in the new year. Let's see how I do. As always, if there is anything you'd like me to clarify or cover in future posts, please send an email to barry@portraitlighting.net. Don't be shy about adding your perspectives, corrections, or requests in the comments section. If you think something is amiss, chances are you're not alone.

First-time parents often ask what is the best time to photograph their baby. I don't think there is one right answer to the question, as you can get memorable images at any age. Nevertheless, I usually suggest 9 months if they'll only be photographing them once in their first year.

Why do I say nine months? Well, actually I should say between 7 months and 11 months, depending on the child's rate of development. The reasons are:


The child can sit up unaided.

The child is not yet inclined to immediately crawl away once seated.

The child is not yet inclined to immediately crawl away when placed on their tummy.

The child has not yet developed an elevated fear of strangers.

The child will usually interact emotionally with the photographer (expressions).

The child is more inclined to smile than at other stages.

The child can be safely propped in a variety of ways.


These are just some of the reasons I'll never pass up an opportunity to photograph a 9 month old. One and two year old children are another story, and a suitable subject for a future post.

Expect a more technically-oriented post later in this week.

A Fill-Light Addendum

You live and you learn, and your ideas about things change. Such is the case with fill lighting for me, a subject that I explored pretty thoroughly in the Topics section of the Portraitlighting.net site. Today I'll mention two deficiencies in that treatment of the subject.

The first came to light when a commentator, on explaining the position of his fill light, said "it's perfect here, if it were any closer it would act as a main light." That statement was seminal for me. The concept was so obvious in retrospect, but somehow it hadn't seemed that important to me. Put another way, if the fill light is too close to the scene, the effects of the inverse-square law will be clearly seen, and the fill light will look like another main light. This phenomenon is seen quite clearly on the website in Example 1.3 www.portraitlighting.net/example1_3b.htm , but as it applies to the main light. In the second image in that example, the light is further back and more appropriate for fill. At that distance, there is a more general and flat sense of illumination, without the added sense of depth and form visible in the first image. Now that doesn't mean the fill light has to be further away than the main light for all applications, but for classic portraiture, where a subtle and indistinct fill is usually desired, it's a good thing to keep in mind.

The second revision relates not to position, but to number. When I wrote the piece on fill lighting, with a few exceptions, fill was considered from a single source. While it is probably true that most portrait studios have one fill light, if they have any at all, that doesn't mean having just one is best or even the most natural solution. After all, most natural-light images receive fill lighting from multiple sources and from multiple directions. Forty years ago, when softboxes and umbrellas were still rare, and large parabolic reflectors quite common, a single fill source was often not the best solution. In order to create an indistinct fill light, some photographers bounced the hard light from multiple parabolics against neutral-colored walls and ceilings to create a soft enveloping fill light. This approach created a fairly uniform fill illumination throughout the camera room, with the added benefit of no distinct fill-light shadow or catchlight in the eye. While this technique has largely been abandoned and is expensive to implement, it still has its place. It's a technique that works well for environmental portraits, especially if you have a bunch of speedlights and the walls and ceilings are reasonably neutral.

Paul C. Buff PLM

I generally avoid mentioning particular brands of equipment, believing that skilled lighters can produce great results from all kinds and grades of equipment. Sometimes, however, a particular manufacturer brings a new and unique product to market, and I have to make an exception. This is certainly the case with the relatively new PLM (Parabolic Light Modifier) from Paul C. Buff.

I had stumbled upon a discussion of this umbrella-like modifier on a forum and did a bit of research on it. It sounded like a great product for a bunch of upcoming assignments, so I dropped a few bucks (it costs little more than a quality umbrella of equivalent size) and ordered one. It comes in different sizes, in silver and satin versions, and with a variety of optional covers and diffusers. I'm not going to go into a detailed review of the entire line or the accessories, as I've only worked with the plain 64" silver version, but I will show a few of my first images with it and share a few of my findings.

If the claims for this modifier were true, I could get a large source, with a smooth punchy light, graded shadows, and an efficiency nearly on par with a standard reflector. I have to admit I was skeptical, as I have never been a big fan of silver umbrellas, many of which exhibit wickedly uneven light. Besides, if this was just a tweaked umbrella with a few more panels and bent into a proper parabola, why hadn't a genius at one of those prestigious lighting manufacturers come up with it years ago? Did it really take a red-haired oddball from Nashville to do it? The answer I found is, apparently, yes.

Before taking the PLM out to do some real work, I did a quick output benchmark in the studio. The output of my Quantum X-series bare-bulb flash with the PLM with was just one quarter f-stop less than with its regular reflector in the wide-angle position. That is surprisingly good considering that the PLM provides about 150 times the surface area of the standard reflector. Admittedly, it would have been a better comparison to have done that check with the Quantum reflector in its regular coverage position, but you get the picture. I also played around with the positioning of the flash tube, moving it fore and aft along the "umbrella" shaft checking the light distribution within the modifier's bowl and how that related to output. Positioning the flash tube as recommended by the manufacturer appeared to optimize both. I did little more testing and packed it up to accompany me for a shoot of a musical group.

I rarely use an untested product on paying customers, but we were doing a lot of our shooting without prior scouting or, as it turned out, much planning at all. The guys and I were just going with the flow, so incorporating the PLM seemed just fine. My customer had submitted several sample photos, each using strong on-camera flash. I hoped to duplicate this look, but with a smoother-looking light and softer shadows. In all the photos shown in this post, the PLM was positioned on axis, just behind, and slightly above the camera. In essence, the PLM became a giant on-camera flash.

The photos shown below were among the last taken that day. The sun had already set and we still wanted to catch a few pictures next to a graffiti-decorated overpass pier. The first image shows our subject leaning against the pier. The PLM was approximately 8 feet from the subject. The resulting light has a fairly smooth quality with some snap, and the shadows are distinct, yet have a pleasantly smooth gradation. A view of the entire group shot at the same distance from the PLM is included to show the fall-off in illumination of this modifier. Keep in mind that this was shot at an 18mm focal length with an APS-C sensor (27mm @ 35mm), so the light and camera were in quite close. The darkness in the lower portion of this frame can be attributed, at least in part, to light blocked by my body. One thing became quickly clear during this shoot: the PLM produces a distinct lighting pattern and must be aimed with care.


Earlier in the day I had used the PLM for a few shots with the group in an ambulance. That portion of the shoot was particularly unplanned. I bungled my lighting, and hadn't noticed that a slave flash in the ambulance had failed to trigger. To make matters worse, the image concept and the busy scene with busy clothing just didn't work for me. I had all but written off the shots when I decided to use some high-radius sharpening and a few other tweaks to salvage an image. The resulting image (below), while not exactly what I had intended, does show how the PLM might be a good choice for an edgy, sharpened look.



The silver 64" PLM is not an all-purpose modifier, but it sure has great potential for a variety of applications. I'm looking forward to doing more work with it, especially using it in close for portraiture, and taking advantage of its graded illumination for feathering.

A Few Observations on Camera Height

Today I'll address a recent request for my take on the effects of camera height relative to a subject's face. What I'll note here is nothing new, and I fully expect many readers to have already come to similar conclusions. I'm going to try to keep this short and to the point, but that's not easy for me.

First, it would be a mistake to address height of the camera relative to the subject without also considering the relationship of the camera's film plane to that of the subject's facial plane. Ideally, one should consider the pros and cons of height (low, level, high) in combination with relative inclination (tilted up, parallel, tilted down). Maybe I'll get to such a matrix in a later post. Today I'll just touch on the most salient points.

Bringing the camera above the subject's eye level has several advantages. An elevated camera position can be particularly helpful when photographing subjects with heavy or multiple chins. Raising the camera and having the subject tilt their head upward will cause stretching of the skin around the jaw, resulting in a more defined chin line and a lighter-looking neck. With the camera moved up considerably, the view of neck can be mostly or entirely obscured. Done skillfully, the photographer can hide a heavy or wrinkled neck and, with a more aggressive head tilt, further stretch loose, inelastic skin for a quickie face lift. Done poorly, the result can look contrived, or just plain awful. A higher camera position may also be appropriate for subjects with a turned-up nose. If the nares are clearly visible, a higher camera position and a slight facial declination may improve the rendition. Subjects with short foreheads, small eyes, short noses, or long, prominent chins may also benefit from an higher camera position. Shooting your subject from a higher camera position can also be helpful when creating tilted perspectives, as when placing your subject along the frame's diagonal. Temper your zest for a high camera position when your subject has a high or broad forehead, a balding or thinning pate, or a small chin. Be careful when shooting full-body views from a higher camera position, as your subject may look shorter.

Using a lower camera position can be tricky. It is rarely flattering for heavier subjects, and often provides a less than flattering view of the nose. Nevertheless, it can be helpful. Consider lowering the camera if your subject has: a long nose (especially, a long hooked nose), a noticeably small chin, or a long or wide forehead. When doing full-body and 3/4 body shots, a lower camera angle can add a sense of height, drama or elegance.

Most head-and-shoulders portraits are photographed at or from slightly above subject eye level. From these moderate positions most subjects render well, but slight changes in camera height and facial inclination can make a big difference. In my experience, the difference of a degree or a centimeter can be the difference between just good and great.

Please feel free to add your perspective (pun intended) on this subject in the comments.

Cool Rule for Facial Analysis

First, let me apologize to anyone following this blog. I've been terribly busy and unable to update it for months. I'm committed to making regular updates from this point forward, and will attempt to incorporate readers' suggested topics whenever practical.

Today I'll mention a simple lighting rule that can make a big difference when lighting an asymmetric face. When I say asymmetric, I' m referring to symmetry in a lateral sense, where one side of the face is smaller than the other. It is quite common to see this in a face, and it is often most pronounced during smiling. For such faces, you'll generally get the best results when your main lighting source shines into the shorter (squished) side of the face. This seems particularly true with short lighting, but is also true in most cases with broad lighting. As with many general rules, there will be exceptions. Faces are complex structures and symmetry is just one element to consider when analyzing the face. I'll talk more about other aspects of facial analysis in future posts. Until then, give this rule a try. I think you'll find it works a surprising percentage of the time.