Photographer Chris Grey is an expert on lighting. He's written seven books on the subject, teaches classes and workshops, and is a strong advocate for precise control in the studio. To see more of his work, or to find his books and DVDs, visit his Web site.
As professional photographers, we should always be looking for ways to set our images apart from those of our competition. For those of us who may shoot strictly for personal pleasure, every opportunity to grow as a visual artist should be explored.
Now, I understand that many photographers are limited to one or possibly two lenses. They are expensive, especially the good ones, and the decision to purchase another piece of high-priced glass should never be made lightly. Still, if you can make a quantum leap in the quality of your work by buying another lens, well, I would strongly recommend it.
As I was learning my craft, I heard and read about a number of “rules” regarding the correct focal length for portraiture. For 35mm, most people seemed to agree that a focal length that was roughly double that of a “normal” lens would do the best job, and that meant a lens of 100mm. A medium format camera such as a Hasselblad required a 150mm lens to qualify as “perfect.” Personally, I think such rules are just so much hooey, and I’ll use whatever I think is best for the job.
A problem that I see with using lenses of short focal length is their inability to soften the background enough to make it unobtrusive. When the background is soft, the subject will stand out, and the image will look more dimensional. Moving your subject far enough away from the background is sometimes possible when working outdoors, although you do run the risk of picking up unwanted details, like cars or telephone poles, which tend to look bad whether they’re in focus or not.
In the studio, the problem is compounded when using strobes. Many photographers buy strobes with sufficient power to light a group from a considerable distance even when using a softbox or umbrella. Generally speaking, these strobes will not power down low enough to use a large aperture for minimal depth of field.
Let’s look at a portrait taken at 70mm (below). I chose that focal length because many folks have only a 24-70mm lens. While you can shoot successful portraits at shorter focal lengths, using the maximum will shorten perspective as much as that lens will allow.
When you shorten perspective, you also narrow the angle of view. My subjects are typically placed about eight feet from the background. At 70mm, even for a head and shoulder portrait, I’ll have a fair amount of real estate behind the subject that I’ll need to light perfectly. In the shot above, my key, hairlight (at camera right), and background light were powered to the same f-stop, f/13. The accent light at camera left was powered 1/3 stop brighter. You see that even with the model eight feet from the background there’s sufficient depth of field to deliver a fair amount of sharpness to the wall.
At 135mm (below), which is a standard prime lens focal length, the background begins to soften up, although focus is crisp over her entire figure. You can see how the angle of view has narrowed even more, with the background looking more evenly lit than in the previous image.
At 200mm (below) the background softens further, the angle of view is even narrower, and focus falls off noticeably, beginning near her ears but becoming unmistakably soft in the hair at the back of her head.
While I’m usually pleased with this result, I sometimes want even more softness to the background and even less depth of field on my model. If you want the same, here are four options for you, depending on your equipment: