Part IV: Portrait Lens
This week features a series titled: “DSLR Filmmaking & Lenses: What You Should Know Now,” a series of blog posts explaining the importance and benefits of specific types of camera lenses (ultra wide, wide, normal, portrait, telephoto) by contributor Jeff Bauer
A portrait lens is considered to be any lens with a focal length between 70mm and 135mm on a full-frame camera sensor. At this perspective, the lens will produce a very shallow depth of field and create backgrounds that appear magnified or flattened. Without this shallow depth of field, objects in focus would be harder to distinguish from the background, causing distracting visuals and unrealistic results.
Let’s talk about perspective for a moment. The focal length of a lens does not determine the actual “perspective” of an image, but rather, it is the distance from the subject, or size, that does. The closer you get to a subject, the more the perspective changes, and turn, dramatically effects the “feel” of your images.
Portrait lenses are perfect for medium close-ups, close-ups, and extreme close-up. This is because subjects in frame will appear to have normal proportions and a nice separation from the background due to the shallow depth of field. You get the feeling that you are closer to the subject literally and figuratively, giving those emotional moments even more power and feeling. If you go with a wider lens, things appear normal and initially less dramatic. If you go with a longer lens, you have to distance yourself from you subject substantially, and without a tripod, things can get shaky very quickly.
When choosing lenses at the portrait length, it’s important to remember the type sensor your camera has, and that a crop factor will be applied as such. For example an 85mm lens on the Micro 4/3 format has roughly a 2x crop factor, effectively transforming into a 170mm lens. Just do the math!
One thing that always gets a lot of attention when talking about long-focus style lenses is bokeh. Bokeh
is essentially the image quality of the out of focus areas. The quality of the glass and the number of physical aperture blades in the lens are key to getting the soft and dreamy look associated with good bokeh. Expensive lenses tend to have more aperture blades, resulting in a smoother iris and in effect, a more pleasing background. Most people can’t tell the difference between good or great bokeh, but bad bokeh is easy to spot, and impossible to ignore.
While quality portrait lenses tend to be slower, heavier, and relatively expensive, it is the ultimate weapon for wringing emotion out of a scene. When used correctly, there’s nothing quite like it.
Next – Part V: Telephoto Lens