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Magazine Article

  


Quality of Light



TECH TIPS


TEXT AND IMAGES BY JAMES SCHMELZER
Technical Representative, F.J. Westcott Company

To create the soft wraparound lighting achieved in the portrait at right, the photographer selected a large light source-the 7-foot Westcott Octibank. The softened effect was enhanced by decreasing the distance between the model and the light source.

Whether you're setting up your studio for a live model or product shoot, creating the right lighting effect is key. Does the subject call for dramatic highlights and shadows or would a soft wraparound light showcase the model or object more effectively? It depends on the quality of light you or your client want to achieve.
For a recent shoot, I wanted a soft wraparound light, because I wanted it to conform to the model's fair hair, makeup, and outfit. Had the model worn dark clothes and had dark features or had I wanted to achieve dramatic highlights and shadows, I would have gone with a smaller light source and a ratio of 3-1 or 4-1 between the highlights and shadows. But to stay in sync with the model's high-key coloring, I chose a lower ratio and kept the light simulating an overcast day.
To create this lighting effect, I used a large light source, the 7-foot Westcott Octibank. Distance from the subject to the light source is a critical factor because the closer you bring the light to the subject, the softer it becomes. Similarly, the farther you move the light from the subject, the harsher the light quality becomes because the light gets smaller compared to the subject.
Too many of us photographers don't know how to determine the correct distance of the light from the subject. We decide by the brightness or by what f-stop we want to shoot instead of figuring out the correct distance for the spread or the softness of the light. When we finally set up our lights, we take a meter reading of the main light. If it's bright we back up the light and if we need more light or brightness we bring in the light. So we are determining the distance of the light from the subject by the brightness, when we should be determining the correct distance of the light by watching to see what changes occur with the light when we move it at different distances from the subject.
For instance, if you have a large group of people and the light is too close the group won't be evenly lit from side to side. That results in bad light depth-of-field. By backing up the light from the subject, the light spreads more evenly across the group, giving you better evenness of light. But remember, the light became smaller, so now it will be harsher than when it was close. That's why manufacturers make different size light modifiers. The bigger the light source, the softer.
Also keep in mind that if you back the light up too far it won't wrap around or give you gentle gradations across the face from highlights to shadow. If you're trying to produce better light results, it's not always the light modifier you use; it's how you use it.
Remember: if you're adjusting the distance of the light to the subject by brightness, you'll miss the most important fact about lighting quality: brightness only determines what f-stop to shoot. The light quality doesn't change because of the f-stop you select. Quality is determined by softness or harshness, wraparound, and light depth-of-field. Keeping the light at the same distance and altering its brightness doesn't change the quality of the light. It just affects f-stop or lens depth-of-field. To determine what qualities you prefer, try the following tests.

To stay in sync with the model's high-key coloring-fair hair, makeup, and outfit-a low lighting ratio was selected, creating the effect of an overcast day. A lighting ratio of 3-1 or 4-1 would have produced strong shadows and dramatic highlights.

Test 1: Moving the light source while retaining brightness
To run this test, you'll need to take 10 exposures with the light at different distances from the subject. Start at 20 feet away and move the light two feet closer each time, so you'll take a photo at 20 feet, 18 feet, 16 feet, and so on until you're 2 feet away from the subject.
With your light (a 45-inch Westcott halo or umbrella, for example) 20 feet from the subject, turn the power of your strobe all the way up, take a meter reading at the subject, set your camera to the correct exposure, and take your first image. Move the light in two feet closer to the subject, turn down the power of your strobe to match the first reading, and take another image.
Repeat these steps till you've taken 10 images. When you review all 10, you'll see big changes in the light qualities at different distances as far as softness, light wraparound, shadow detail, and light depth-of-field are concerned.

Test 2: Adjusting brightness while retaining the distance
To run this test, we'll take eight images with the light, a 45-inch halo or umbrella, at the same distance from the subject, turn the power up and down to be able to shoot at every aperture, and see that it doesn't matter what f-stop you use because the quality of lighting doesn't change with brightness.
To start, place the main light at a distance of 10 feet from the subject and turn the power up until your lens reaches its max setting, usually f/32. Take your first image. Then turn the power down on your strobe until your meter reads f/22 and take another image. Repeat these steps at f/16, f/11, etc., up to f/4.
As you compare these images, you should notice there's no difference in the light quality among them. Ergo, the most important factor when setting up your light source is the distance from the subject.
A lighting footnote: use the right accessories to produce the mood you want. Otherwise, it's like driving a Ferrari up a snow-covered mountain when you should have taken a Range Rover.


   







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