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The 90-Percent Rule Of Lighting In Photography

It’s About Absorption And Reflection

You often hear about percentages, sometimes in statistics, like 75-percent of all statistics are made up, which often leaves you wondering about the accuracy of such numbers, but when it comes to photography, one percentage that is accurate is the 90-percent rule of lighting. It’s not just a rule, it’s a fundamental and principal of photography every photographer should comprehend, after all, lighting is the lifeblood of an image and without light, there is no photo.

Mode photo 90-percent rule in photography lighting

It's easier to photograph a light complected model in a light top like this photo of Jenni, due to the 90-percent rule of lighting in photography.

Simply stated, the 90-percent rule applies to reflected and absorbed light. Whatever is pure black, will absorb 90-percent of the light that strikes it, whatever is purewhite will reflect 90-percent of the light that strikes it. As simple as that seems, many photographers forget the other part of the rule, there is 10-percent light reflected from pure black and 10-percent of the light absorbed from pure white. The key word in all the states about the 90-Percent Rule is “pure.”

However, a photographer must comprehend that not all black or whites are pure, though many are close. So to use the 90-Percent Rule effectively, a photographer must learn to judge shades of gray, or all the tones and mid-tones between pure white and pure black. In photography, black and white and the shades in between are not colors, they are tones and some tones are more reflective than others. The darker the tone, the more light it absorbs and the less it reflects, the lighter the tone, the more light it reflects and the less it absorbs.

Once a photographer understands everything to the black side of the tonal scale (left area of histogram, shadows) is absorbing more light and everything to the white side (right area of histogram, highlights) of the tonal scale is reflecting more light, we can apply this when metering our subject that is illuminated by artificial light. If we build a set, then meter it and the result is F/8 off the flash meter, that would be the actual aperture we’d use to properly expose the set, however, throw in a model/subject in the set and now you’ll have to consider her skin tone because as photographers we should expose for our subject, not the set. So what tone is our subject? Is the subject darker than middle gray? Is our subject lighter? How much darker or lighter? These are things a photographer must take into consideration to adjust their exposure.

Now many will argue about the accuracy of the meter based on 18-percent gray, a middle tone is all that is needed, but in reality, when you take the 90-Percent Rule into account, it’s only true for the scene, not the subject. The flash meter is measuring the light falling on the subject, incident light, not the reflected light the digital camera’s sensor will capture from the subject’s actual skin. Learning to judge how much light a model’s skin will reflect takes skill, but the easiest solution is to stop down 1/3 of an F/stop for lighter than average skin tones and to open up 1/3 of an F/stop for darker than average skin tones.

Think of your incidental flash meter as starting point based on 18-percent gray, similar to the meter in your digital cameras (DSLRs). The color of 18-percent gray is close to the average gray of street asphalt (not black top) found on most highways and parking lots. I’ve worked as a photographer/photojournalist in almost 40 countries, photographed tens of thousands of people and I still have not seen anyone with asphalt gray skin tone.

Black on Black Model Photo, 90-percent Rule of Lighting in Photography

When photographing a dark subject, or in this case dark clothes against a dark background, use white V-flats on each side of your subject to bring out separation and detail as in this photo of Candice.

During a photo shoot, I will consider the skin tone of my subject, or the correct exposure for my subject’s skin tone, I then look at the actual scene and adjust my lighting to match—it’s like the rule of posing, pose the model first, then light for the pose. In essence, I light the model first, then light the set. As example, since this article focuses on the 90-percent rule of lighting in photography, let’s pretend we’re photographing a dark subject against a dark background and we must maintain that dark background. If the lighting is improper the subject will disappear into the background and/or the background will not appear as dark as it was intended.

While sometimes no separation of the subject from the background can make for interesting photographs, it’s usually more appealing to create some separation of the subject from the background, which is easily done by simply understanding the 90-percent rule of lighting in photography. Separation of the subject and the background also makes our subject standout or appear in front of the background—an important element in people photography—in addition to the fact that many art mediums like photography are two-dimensional, separation will often add another dimension in the overall photograph.

High key photo of model

When photographing white on white, use black V-flats on each side of your subject for separation from the background and to provide detail in your subject's clothing.

Since we see in three-dimensions, any third dimension illusion we create through lighting provides for a more effective photograph. In the above situation I painted a dark subject against a dark background, or a low-key scenario, though the 90-percent rule applies just as equally when a photographer is faced with a model dressed in white posed in front of a white background, or a high-key set. Whether it’s a low-key or high-key scenario with matching backgrounds and subjects, if a photographer understands the 90-percent rule of lighting in photography, the resulting image will reflect this grasp of knowledge.

For example, let’s take white on white. The key here is to take at least two, black foam-core panels and place them on each side of the subject as close as possible without intruding on the frame of the image. These black panels help subtract light from the sides of the subject while reflecting some black tone back into the subject’s sides. This affect will create an effect of a thin outline of the subject’s white clothing and add detail into the subject’s clothes from the white background, thus the badly needed separation of the subject from the background is created through the absorption and reflection of light.

The same happens with black on black, a photographer simply has to place a white foam-core panel on each side of the subject so the reflected light from the white will have the edge-building effect on the subject’s clothing. It’s all about separation through absorption and reflection based on the 90-percent rule of lighting in photography.

When using these white and black foam-core panels, or cards, simply place them parallel and close to the sides of the subject without physically entering the camera image frame. This method works great when you only have two cards, though the ideal method is four cards, two on each side and affixing them together with gaffer’s tape to form a V-shaped wall with the V-point facing away from the subject. Ideally 4-foot by 8-foot foam-core boards work best, especially if you use the type with black on one side and white on the other side. This is more efficient since you simply rotate the V-flats to use the side you need for a given scenario.

First Book Cover Featuring Playboy Playmate Holley Dorrough

My first book cover featuring Playboy Playmate Holley Dorrough involved using black cards to bring the detail in her platinum blonde hair out.

Now this technique is not limited to high-key and low-key studio scenarios, let’s take the hair color of a model as an example. If your model is platinum blonde haired, with dark, tanned skin, her hair will obviously reflect more light than her body. The human eye is forgiving, so we don’t notice the difference, but the camera is not forgiving, it only captures reflected light accurately based on our camera settings. Thus the potential for blown-out highlights, the hair in this case, is highly probable.

Obviously we’re exposing for her skin so this will cause the hair to overexpose, though the solution is simple, have an assistant hold or place black cards, again out of camera frame, around her head to reflect black tone back into her hair, as I did in my first book cover of Playboy Playmate Holley Dorrough.

In summary, as a photographer, knowing that the 90-percent rule of lighting in photography is not a made up statistic but a highly accurate number, plus understanding how it impacts every element in a photograph, can make our photography great and not mediocre. With that I close, as in all my books, let’s not forget the men and women who serve our country to protect our freedoms, God Bless them all, their families and friends, Rolando.

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12 Comments

  1. Rolando,

    While I agree about the 90% black/white reflectance you discussed, I kept looking for a way to simply utilize that information… and maybe I am just slow, but I didn’t find it.

    In my photography teaching of studio lighting, I tell students to take an incident light leading at the subject position, to get an overall scene exposure. Then take a reflected light reading (using ambient light is fine) off the subjects skin, usually the forehead, and compare that reading to 18% gray. If the reflected light reading is more than 1/3 to 1/2 stop different than 1 stop lighter than 18% gray, the overall scene exposure needs to be modified so that the reflected light reading off the subjects skin is approximately 1 stop lighter than the original scene incident light reading. This provides an exposure which will yield good shadow detail in both the highlights and the shadows, for both caucasian subjects and people of color. The final scene exposure is then the modified incident light reading at the subject position. The final skin tone of the subject can then be decided during the printing process or the computer manipulation of the final image, but you now have sufficient detail in both highlights and shadows to make any corrections you desire.

    The background tones are then determined by making an incident light measurement of the background paper or material. Pure black paper will reflect 2 stops less than 18% gray, pure white paper will reflect 2 stops more than 18% gray. For a pure black background, subtract background light (change light angle, flag the key light, or move subject farther away from background) to provide 3 and 1/2 to 4 stops LESS reflectance from the background than the incident light on the subject, keeping in mind that 1 and 1/2 stops less light on the background when added to the 2 stops less reflectance of the black paper will provide the 3 and 1/2 stops less reflectance needed to get a solid black.

    Conversely, add enough background light to a white paper background to provide a 3 to 3 and 1/2 stops more reflectance off of the white background, compared to the incident light on the subject. Again, keep in mind that 1 stop more light falling on the white paper background plus the 2 stops more reflectance from the white paper (when compared to the subject) will provide the 3 stops lighter background necessary to have it photograph as pure white. (Note: The background reflectance should never be greater than 3 and 1/2 stops more than the subject, or the white paper can become a light source in itself and create flare in the camera lens, leading to degraded image characteristics which look like a fog over the entire image, but primarily affect the blacks and dark tones.

    Of course, for intermediate tones in the background, interpolation of the above can be used to obtain any tone background desired.

    I did really enjoy your discussion of the use of white and black V-flats for manipulation of the edge characteristics of the subjects. I often use 4′x6′ V-flats both in both white and crumpled aluminum foil covered versions, as both reflectors and large flags. The use of black V-flats for edge modifications for high key lighting is intriguing and will be tried. My technique of getting a similar effect is to use a large 7′ diameter umbrella directly behind the photographer as the key light (but elevated somewhat, with the center of the umbrella at approximately the photographers head), with no fill light. That does an excellent job of creating the darker edges on the body/figure.

    Many thanks to you for your outstanding articles and links!

    Don Becker
    http://www.donbeckerphoto.com
    and
    Faculty member and Technical Director
    Washington School of Photography
    Bethesda, MD 20814
    http://www.wsp-photo.com

    • Don,

      Thanks for the great information. Perhaps I should have been more clear, but my references for metering pertain more to using artificial lights, such as studio strobes. Obviously when I’m shooting with natural, reflected light only, I meter in the reflected mode, not the incidental mode as reflected metering is more accurate in that type of scenario. Again, thanks for your input and I look forward to your future comments, Rolando.

  2. I really enjoyed the wrute up. Most I look for informative articles such as these that explain a little more into the elements and values of lighting a photograph rather then just stating that they exist. Thanks

    • Thank you, and please spread the word about LensDiaries.com to others, thanks!

  3. Very interesting article, well written. Thank you.
    I would question the conclusion: I don’t see how high tech soldiers bombing two third world countries 10 thousand miles from home to rubbles are protecting anyone’s freedom. And why they should be blessed. They are there to protect other interests (and spend your money that should be spend educating your children).

    • Francesco, thanks for your thoughts, however, having served 8 1/2 years active-duty, U.S. Army (E-6), and 8 1/2 years civil service U.S. Air Force (GS-12), I can tell you don’t understand how the military works. First of all, all soldiers, sailors, airmen and marines take an “Oath of Enlistment” to protect and defend the Constitution of the United States and those liberties it grants us. In that oath, we swear to protect the United States, from enemies, both foreign and domestic, along with obeying the lawful orders of the President and those officers appointed above our ranks. We do not question lawful orders whether we believe in them or not, we execute them regardless of our political and religious beliefs. If the military service members fail to carry out lawful orders and question every command and order given to them, then it would not be a military, it would be total chaos, lack of discipline, and lack of leadership.

      The military doesn’t waste “our money,” (and by the way, they pay taxes too), politicians do, and if someone has a disagreement with how our country operates, take that up with the politicians. Military members don’t play politics, they follow core values and carry out the METL (mission essential task list) placed upon them. Our military is a volunteer force of dedicated, patriotic people and no one is forced to join. They do what they are told by the commanders and those tasks come from the politicians down through the chain of command. I can’t think of one time that every person in the military was at 100-percent in “personal belief agreement” that a mission was correct as ordered. You can’t blame the military for political agendas, as the military can only do what it’s ordered to do, again, regardless of each individuals personal beliefs–military members do what they are told and do not question authority. If you want to blame someone, blame the people that don’t exercise their right to vote for their elected officials. U.S. military members are not responsible for political decisions, elected officials are responsible for all military missions.

      With that I close by saying, feel free to comment about the photography blogs/articles, but please do not use my blog to advance your political beliefs, save that for political forums, blogs, etc. We focus on photography, and I would not be allowed to practice that photography, or publish this blog, without those constitutional freedoms I enjoy, and without the military, they would not exist. In all my books, and most of my blog posts, I always thank and bless our men and women military members, their families and friends, because regardless of my or your political beliefs, they pay the ultimate sacrifices that allow us to agree to disagree. My loyalty to the military all that serve and have served, will never be questioned, for I am a Veteran. And unless you have ever served in the U.S. military, regardless of what I say, what military story I share, etc., you would never truly understand. All the best, Rolando (former U.S. Army Staff Sergeant, active-duty)

      • Not to get too deep in the political thing here, please let me say that the comment you left this person was the best and most complete explanation about our military and why we do what we do that I have heard in years. I thank you for that and wish that we had a few politicians these days that could explain things as clearly as that.

        • Thank you! I do my best and I’m proud of my military service as thank those that continue to defend our freedoms. Thanks!

      • Thanks Rolando for sharing all your knowledge. Also great to hear you support those who put their lives on the line for their country and people so their children can have education down the line….

        • You are welcome and as a former Staff Sgt. in the active-duty U.S. Army, I’m always supporting our service members and veterans. Thanks!

  4. Thanks for the article! I enjoy following you on twitter. I’m pretty much a beginner, only owning one light, a manual flash. Anyways, I’m having some trouble envisioning the 4 card V-shape, any chance you could elaborate on that.

    • Brandon, you’re welcome! Basically take two, 4-foot by 8-foot foam core panels (think the size of a sheet of plywood), black on one side, white on the other, available at your locale graphics supply store–ask them, they will know what you are talking about. Then when you get them, lay them on the ground, same color up, tape them edge to edge (8-foot edge) with black gaffer’s tape (available from Rosco), from top to bottom. Once they are taped on both sides, stand them up (tall, 8-foot) and position them so they form a V and support themselves standing up with no help or stands. That’s a V-flat. 8-foot tall, 8-foot wide, black on one side, white on the other. I hope that helps and I’ll try and get a photo of one for a future blog article.

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