Bare-Tubed Strobe

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A bare-tubed strobe is about the closest one can get to a true “point” light source. Without any modifiers, not even a basic parabolic reflector, the light will emulate sunlight, and its specularity, sharpness, and deep shadows will increase as the light is moved farther from the subject. While this light may not be especially attractive for, say, a family portrait, it can be perfect for many other subjects. Those of you engaged in advertising photography should play with this lighting style, as it has recently become pretty popular.

The subject-to-background distance will determine the strength of the light on the background. The Inverse Square Law tells us that light traveling from point A to point B will be only 1/4 as strong from point B to point C when point C is twice as far from the source as point B. This means that if we want the light to be evenly exposed over a wider distance, we must move the light farther from the subject.

To create our first image (4.1), the bare-tubed main light was set about 8 feet from the model, who stood about 8 feet from the white background. Notice how evenly the model is exposed from the top of her head and down her black outfit all the way to the bottom of the frame. Since the main light was placed almost directly over the lens axis, the white background is also evenly exposed but becomes gray because the strength of the light has been lessened by distance. If the main light metered f/11 at the subject, it would meter f/5.6 (1/4 the strength of f/11) at the background.

We can use this principle creatively. To create image 4.2, the same snappy light was used, but this time it was placed about 4 feet from the model, who maintained her distance of 8 feet from the background. Two things happened because the light was placed closer: it lost strength more rapidly (look how it falls off about halfway down her figure), rendering the background darker, and the model’s shadow began to creep up the background because the strobe itself had to be lowered to maintain the same shadow angle.

Bare-tubed strobes can throw quite sharp shadows, especially when the subject is close to the background, and you can control the sharpness of those shadows by changing the distance of the main light to the subject. The farther the main light is from the subject, the sharper the shadow will be.

When we go back to the original light-to-subject distance of 8 feet but snug the model up to the background, we can get an almost perfect white background and a terrific dark shadow. Bear in mind that you can never get a perfectly clean white background because the paper (or any other material) is not a perfectly clean white and will not photograph at a value of 255 unless it’s been lit separately and slightly overexposed. Even though this exposure is darn near perfect, the value is about 250 at its brightest, with still enough detail to register on a print (although a little more work in Photoshop would help). Where the light falls off, near her camera-left thigh, the value is about 220. Doubling the main light-to-subject distance to 16 feet would increase the evenness of the exposure by 50 percent and increase the apparent sharpness of the shadows. See image 4.3.

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I prefer to set my main light with the strobe tube angled sideways to the model, not head-on. I don’t want any of the light to kick off the front of the unit and soften the shadows. Although the manufacturers don’t recommend that you do this, you may find you’ll get an even sharper shadow if you remove the dome that covers the flashtube and modeling lamp. The dome is there to protect you and your subjects should the tube or lamp explode when triggered. That’s never happened to me, but take note that I’m not recommending it, either. It’s your call.

Place your subject in front of a softbox that is at least large enough to cover the subject so you can extend the white (if needed) without having to do any major retouching on whatever parts of the model extend out of frame, and you can use the bare-tube technique to produce very interesting images with sharp, sunlight-like shadows against a pure white background. This is a lighting scenario that you don’t see often, because it’s generally not on anyone’s recommended shot list. The bottom line is that it’s pretty darn cool and should be tried whenever you think you have a subject that deserves it. Of course, there are many derivatives of this technique, many of which you can discover for yourself, just by playing with your toys.

For the first image (4.4), I placed the bare-tubed strobe about 6 feet from the subject and about 4 feet over her head. You may think that this is an unusually high angle for a main light, and you’d be correct. For most applications, it is. However, you must balance the height of the light, knowing that most sunlit images are made with a higher source, against that of perfect portrait lighting. Of course, the shape of your subject’s head and face, the angle at which the face is presented to the camera, and the effect you wish to achieve will help dictate the right spot for the light. Also, when you move a bare-tubed strobe farther back (to get depth of light, an even spread of light over a given distance), you’ll have to raise it higher to get an appropriate and attractive nose shadow.

I’d placed my model about a foot in front of a very large softbox, a Lastolite HiLite. At 6×7 feet, it’s a source large enough to wrap around the subject while providing plenty of white space on each side. I measured the output from the box and powered the main light to be 1 full stop less. This was my working aperture and guaranteed the background would be completely white without flaring into the lens and softening contrast.

Next, I added a beauty bowl to the bare-tubed strobe. The look of the light is similar, although the spread is more concentrated in an arc that extends from the reflector. Note that the falloff of the light looks substantially different than that from the bare tube. Also, as you can see, the shadows are a bit softer. It’s just another option, but one with its own personality. See image 4.5.

Bare-tubed light looks great on black, too. My model was about 8 feet in front of a black paper sweep, and the strobe was about 6 feet to camera left. I’d flagged the light with a piece of black Roscoe Cinefoil to keep all light off the background. I’d also moved a black bookend in behind the model to absorb any light that might bounce back from a wall.

Because the light is strong and omni-directional, I clamped another piece of Cinefoil to a stand and created a shadowed area that I could move around in without fear of lens flare. See images 4.6 and diagram 4A.

Like everything I write about, I encourage you to try the bare-tube look for yourself. It’s one more bullet in your creative arsenal, and you’ll find it’s a very large caliber, too. Just spend some time playing with it to understand it.

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