With all the emphasis on maximum aperture (bokeh!) these days, focal length might not be the first factor you think of when it comes to selecting a portrait lens—but it's certainly an element not to be overlooked.
Most photographers tend to use a moderate telephoto lens—70mm to 200mm—as that range generally produces the most flattering angle of view for most people's features. But that's a pretty big range, so what's the difference between an 85mm lens and a 105mm, really?
Well, before you say "about 20mm", let me tell you that this is where the debate gets a bit nebulous and into the territory of personal preference. And since it's largely subjective, there's no one answer as to what focal length is right for everyone. But perhaps exploring this topic a bit deeper will provide some clarity.
Let's start with some background info.
What Is Focal Length?
Focal length—commonly measured in millimeters (mm)—determines the angle of view for a lens. The lower the number, the wider the angle. The higher the number, the narrower the angle. On a full-frame camera, a 24mm lens has about an 84-degree angle of view, while a 200mm lens has a much narrower 12-degree angle.
The difference between those two lenses affects how far you have to stand back from your subject to capture a portrait of their head and shoulders, so, because of the physics involved, it also has a huge effect on the way your subject will appear in the photo.
What Does This Look Like In Practice?
Take for example these portraits by photographer Dan Vojtêch. He shot them using different focal lengths, while maintaining similar framing throughout.
You should be able to discern a pretty big difference between the first and last image, but just to drive the point home, here are the photos in quick succession.
You can tell how the facial features seem to flatten out as the focal length increases, and this has to do with the angle of view getting narrower. Inversely, as the angle of view gets wider, features like the nose, eyes and ears appear differently in relation to each other.
The subject starts appearing more natural to our eye at about the 35-70mm range, hence the "normal lens" term generally applied to glass in that range. But as you go even longer, to 85mm and beyond, that's when the face seems to widen and the ears are pulled forward to look more proportional.
So, Is Longer Better?
Not necessarily. A wider and flatter face doesn't flatter every subject, so this is where having some options comes in handy for a portrait shoot. Some subjects, especially those with fuller, round faces, can actually benefit from a wider angle of view, as it has a slimming effect. Inversely, those with narrow faces can benefit from a longer lens. It's a matter of making subtle adjustments to achieve the right balance.
This is where zoom lenses can be a lifesaver, as they give you a range of focal lengths you can play with to find the sweet spot. If you want to maintain the optical quality, and often, wider aperture of prime lenses, you might want to have several on hand to stay flexible.
Finding the right focal length for a perfect portrait might take some experimentation, but doing some leg work will only help with the end product—and that's what really counts.