Photography Lighting (Part 1)— Studio Portraits
(In this part 1 of 2 series, we will first discuss lighting in studio portrait photography)
One of the basic elements for creating photographs is light. Without light you cannot expose a clear image. Light brings out the sharpness, details and colors in images, so it is important to get enough of it to make a good exposure. I don’t think there is a perfect exposure, only a correct setting in camera. That too can be subjective, but that is the difference between a good and a bad photograph.
The camera allows light to the image through the lens, which is then captured on film or a digital electronic sensor. This results in the exposure of the image, which can be saved to a computer for editing or it is captured on film as a print. Getting a clear and sharp image is dependent on how the photographer sets the camera. For great quality it is about the lens and sensor combination with good lighting. It is also advisable for the photographer to understand the different shooting modes and use manual mode for more control of their camera’s exposure.
The Theory of Light
A source provides the light for an image. Light consists of particles called photons, which illuminate the image. Based on observation, the more light the more clarity and less noise in an image. If the lighting is good, the image’s midtones are balanced. The histogram would show the graph of the RGB channels or grays toward the center. If the image has too much light, it will be overexposed. This leads to clipping on the histogram as it shifts toward the right. When the image has too little light, it is underexposed. The graph on the histogram will shift toward the left.
For more about histograms, read my article about how it helps to understand image exposure at this link. Light also has color temperature properties due to different wavelengths. A more detailed explanation of how color affects images is explained in this article.
Studio Setup
I will go over quickly a typical studio setup. This is really not something absolute because photographers don’t use the same setup to create their images. This is a part of the creative process, but follows a standard way to setting up.
First you will need a backdrop. The traditional backdrop is a roll of white paper placed on stands that is put behind the subject. It provides a neutral background as well. Photographers can experiment with the colors and usually rented studios can provide the backdrops along with the stands. Some photographers don’t use backdrops and would rather shoot against the studio’s walls.
Lights are definitely needed, especially in dark studio environments. The light, also called strobes or flash, becomes perhaps the most important element to image creation. The studio should provide an ample power supply for operating the lights. Depending on how many lights are being used, if the studio does not have enough power the lights won’t operate. If an overload occurs it could also trip the breakers in the circuit. The lights will also need to have stands where they are mounted on.
The last thing the studio should have, in relation to creating images, are extension cables and power strips. Photographers need to be able to place lights where they want and sometimes it requires an extension cord to power the lights.
Basic Lighting Configuration
The basic lighting setup in a studio photoshoot is called Three Point Lighting. Simply explained, we can use three points as light sources for a subject.
Key Light — Also called the main light. This is really all you need to create an image. The key light is strategically placed in front or toward the part of the subject’s body (e.g. face, hair, etc.) that needs light.
Fill Light — This provides more balance to the lighting on the subject. It can be placed close to the subject to fill in shadows to give a more even light. The fill light can even be a reflector or white board that bounces light back to the subject.
Back Light — Depending on what the photographer is trying to create, the back light is used to overexpose the background to keep the subject as the main part of the image. A light or several lights can be placed behind the subject to blow it out, to create more separation between the foreground and background.
The placement of the light is also important, but there is no actual way of doing it. Exploring different angles and distances is trial and error. This is why a photographer will need to test the light setup first before they begin the actual shoot. A light meter is one instrument photographers can use to get settings for a proper exposure, but more experienced ones will use settings they already know works.
The Guide Number
When shooting with any sort of strobe or flash unit, there is a formula to use that provides an approximate value to get the correct illumination on a subject. This is called the Guide Number (GN) and states:
The light output of an electronic flash is equal to the distance of the flash unit from the subject multiplied by the f/stop.
GN = D * fD = Distance From The Subject
f = f/stopFor Distance, given the value of the GN and the f/stopD = GN / fFor f/stop given the value of the GN and Distancef = GN / D
In my own photoshoots, I do the calculations quickly just to get an estimate of how far or how close the lights should be to the subject. I use the reference from the strobes given GN information. Later I will demonstrate why I use the GN when using a certain f/stop to find the flash to subject distance. In reality, most photographers don’t actually follow the GN formula’s exact calculations. It is a good reference to know.
This follows the rules of the Inverse Square Law, which states that light has a different intensity based on its distance from a light source. The relationship of GN with the distance shows that the brightness of a flash declines with the square of the distance while the amount of light admitted through an aperture decreases with the square of the f/stop.
To explain this in simpler terms, the closer your light source is to your subject, the more light you have. The farther away your light source is to the subject, the less light you have. Light loses intensity every time the distance is squared, so the illumination declines from a distance of 5 feet to 25 feet. When the aperture opening decreases, it means less light when the f/stop is squared. Therefore an f/stop from f/4.0 to f/16 permits less light to the aperture. It is good to shoot in manual camera mode when doing this because the photographer has complete control of their camera’s settings.
Lighting Techniques
There are different sources for light. We use what are called modifiers to alter the type of light from the source to the subject. Here are 5 types of lighting techniques with their modifiers along with sample images containing their exposure settings from camera RAW (Note: the images provided were retouched. Photo credit Vicente Tabora Photography © All Rights Reserved).
Softbox
The softbox diffuses the light to a softer and more even lighting on the subject. This modifier is placed on the light stand in front of the light source. The lights are triggered either via a cable connected to the camera (trigger cable) or a wireless trigger (e.g. pocket wizard).
The effect gives a soft light that smoothens the subject’s skin that can mask many details. This is sometimes good since it can reduce retouching in post when working on the skin. Softer light is also more flattering for portraits since it gives a more pleasing look to the subject, ideal for beauty and headshots.
A softbox is often used with strobes, but it can also diffuse constant lighting sources which are non-triggered. Constant lighting are also placed on stands around the subject to provide a light source but doesn’t require it to be triggered. This is considered even more balanced when the light is placed in a proper manner to the subject.
The power of the light source, measured in Watts (W), determines how powerful the light source is. More powerful sources can provide more light, thus the best clarity for images. Professional studio lighting often use light sources with a power rating of 150W and higher. For light sources less than 100W, it is important to shoot in RAW format to recover details in the image during post. I notice you can still get good results after post when your light source does not have the power > 100W. Image editing software will allow the image’s details in shadows to be recovered but only if it was in a RAW image format. Otherwise, just brightening the shadows will bring out more noise.
Beauty Dish
A beauty dish is a parabolic metallic dish that bounces light from the strobe to the subject. It provides a much harder light, boosting highlights and details in the skin and colors. I use a beauty dish mostly for product or detailed beauty shots for makeup artistry. Comparing the beauty dish to the softbox, one will notice the hard light hitting the subject. The light which bounces from the dish is reflected from a smaller plate that covers the light head of the strobe. Since the dish has curvature, it can bounce plenty of light toward the subject. The light falls hardest around the center but falls gradually off the edges of the subject.
Images created using a beauty dish will require some more retouching, especially if it exposes too many flaws on the subject. The skin in particular would require some retouching if it exposes too many unsightly flaws. This would be done in post to cover up blemishes or scars, something that doesn’t look too flattering for ads or publications. Perhaps a softbox would be ideal for beauty portraits, but the beauty dish is used for a special reason. While softbox are excellent for beauty, the beauty dish is needed when details in colors and skin tone and texture is required. When shooting for products that need to showcase these features, the beauty dish shows a better light on the subject. The light sculpts the features with beautiful shadows and catchlights in the eyes.
There are also softbox/beauty dish combinations that combine soft light with more highlights. One can easily overexpose their image when using a beauty dish, so be careful to check that the histogram is not too much shifting toward the right. In camera displays can also show where the clipping is occurring and these indicate hotspots that lose details that may not be recovered in post.
A beauty dish comes in different sizes measured by its diameter (measured in inches in the US). The larger the diameter, the more light the dish can bounce. However, that would be more ideal for high powered light sources that are >150W, but at the same time can help reflect light to a larger area as well.
Umbrella
The umbrella is a common light modifier that is shaped parabolically just like the umbrella used on rainy days. The strobe can also be placed to shoot directly through the umbrella as a diffuser, or it can be placed to bounce light back to the subject. It bounces diffused light back to the subject, providing a softer light that can cover a large area that is under the umbrella. The results can emulate lighting from a outdoor source based on the color temperature scale.
Since it has a broad lighting coverage, it is ideal for full body fashion shots used for catalogs and e-commerce ads. This requires much more power from the lighting source (> 150W) for the best results in quality and lighting. Taking group shots in studio can work with any light modifier. The problem is a softbox may not provide enough light while a beauty dish could be too harsh. An umbrella provides great lighting for groups since it can diffuse light to a broader area.
Umbrella sizes are also measured by their diameter in inches in the US. The largest diameter is the best for full body and group shots. A good setup for fashion shoots is to use one large diameter umbrella as the keylight, with a 2 sidelights or a single backlight. Another technique is using two umbrellas as the keylights with a single backlight. There is no correct result, photographers will need to play around with the settings until they get a decent exposure.
Bare Bulb Strobe
There are cases when the photographer wants to shoot with a bare bulb, or just the strobe without any diffuser or light modifier. In this case, the photographer wants to blow the highlights to a certain extent by getting the most light from the source at its power rating. This can create a high key result in the image, which brings out light tones and whites. At times the effect may look somewhat overexposed as the graph on the histogram will shift toward the right. This is actually fine, so long as the subject is not too overexposed.
Another reason to shoot with bare bulb light, is to provide back lighting. As a back light, the photographer’s aim is to expose the subject while blowing out the background. The idea is to create overblown highlights to make the background totally white. This requires a single or two back lights that are pointed toward the backdrop in the studio. One reason I do these shoots is for catalog or look book work. The model needs to have a clean background that will allow more of the eye’s emphasis on the model and the clothing.
In the sample image, a simple white background is used. The problem is if there is no back light, the background will appear too gray and there will be the presence of shadows. To remove the shadows or lighten the background, high power light sources are used to blow out the background. The model must also not be too close to the backdrop to prevent highlights from bounced light affecting the image. The subject is lit by a single key light which was an umbrella, while 2 bare bulb back lights to blow out the background. Further processing in post to set the background color to white (R=255, G=255, B=255) can be performed.
Flash
This technique makes use of the on camera flash unit or a hot shoe mounted speedlight (i.e. flash unit). What I like about this technique is it can work outside of a studio just fine. In studio the subject is shot against a wall or backdrop, but any sort of backdrop can do.
In the first photo example, I want to know what distance I need to be from the model based on the speedlight’s specifications. I set my f/stop to f/13 with flash set to TTL at full power set to 1 (Nikon SB-600 speedlight with a GN = 42 meters / 98 feet at ISO 200). We are going to find out using the GN formula.
D = GN / fGN = 42
f = 13D = 42 / 13 = 3.23 meters or 10 feet
The calculation requires me to be at least 10 feet from the subject to get the correct illumination. In reality, I can only estimate my distance since I won’t go around measuring my actual distance every time I take a shot. I also bumped up my ISO to 400. There is no rule that you have to use ISO 200, that is just in reference to the GN. The result has a more high key look with direct flash on the model in the photo.
The next example was shot with a more low key result. The shadows and darker tones dominate here. In this case I was much farther away from the subject, but had a wider aperture opening. The light was also bounced from the wall, so the floor has the highest darks in the image. The thing about GN is that you don’t have to follow it to get image lighting accuracy. It is just a guide or reference.
In this shot I used a 35mm focal length using the on camera flash unit on a Nikon D7000. The GN value for this flash is 12 meters / 39 feet at ISO 100. To get an estimate of what f/stop to use at a distance of 20 feet away (about 6 meters approximated). I calculate using the GN formula.
f = GN / DGN = 12
D = 6f = 12 / 6 = 2.0
According to my distance, I need to use f/2.0. Due to the distance away, there is less brightness so the image looks more low key. The on camera flash also does not have as much illuminating power as an off camera strobe, but the lighting is quite direct and can be used as a fill light.
Diffusers, mini softboxes and other light modifiers can be placed on the speedlight. Many photographers use them during event photography. The speedlight can also be mounted on a stand and used to provide light for softboxes, umbrellas and even a beauty dish.
Synopsis
Light is important in taking photos and image creation. When shooting in studio, strobes and speedlights are the main light sources. The Three Point Lighting configuration is one of the most common setups used for studio photography. There are different types of light modifiers that can be used to provide lighting based on the type of image the photographer wants to create. The GN provides a guide to photographers for getting the correct illumination on their subject based on the value provided by the vendor. An important thing to take note of is that the more light, the less noise, the better the clarity of studio portrait images.
In the real world of commercial studio photography, different combinations of lights and light modifiers are used. Sometimes a single key light is enough to shoot with. Other times, like when shooting an editorial, different types of lighting systems are used to produce the best image. The lighting can be determined based on the creative vision of the photographer or director. There is no absolute way of doing it so there is freedom to explore what works best for the photographer.
