Which Prime Lens Is Right For Me?

I recently had a young film student reach out to me and ask if a 50mm or an 85mm prime lens would be better for shooting interviews. He plans to start work on a documentary in the coming months and wants his interview compositions to have a nice, soft background. If you're currently in the market for a good prime lens and want to know which one to rent or buy, this post is for you.

Here's the short answer: get both. The 50mm and 85mm prime lenses are great choices for shooting interviews and are excellent additions to your kit. You will find yourself reaching for both constantly throughout your shoot. 50mm is a popular focal length because it most closely mirrors how the human eye perceives the world. But let's say you can't afford to purchase or rent both. What then? Well, here are a few other considerations to help make up your mind.

Composition

How do you want to frame each interview? If you want each interview to be framed in a medium or medium-close shot, an 85mm lens might be right for your project.

If the background itself is important to the story, or to the person you're interviewing (like a craftsman, artist, musician, actor, etc.) you might go with a 50mm lens (or wider) so the viewer can see more of the space. Remember, not every interview has to be a super-tight, 20/20-style frame.

Crew & Conditions

Sometimes your circumstances dictate which lens is right for the job. Will you be shooting in a controlled environment? Will you have a crew helping you?

The film student who first asked me this question plans to shoot on his own, out on the street. So, most likely it will be a very noisy environment. If you find yourself in a situation where you have to handle interviews on your own, my recommendation is to shoot on a wider lens. This means you will have to move the camera closer to your subject, which is beneficial for the following reasons:

• It will give you better reference audio for post-production.

• It will allow you to stand closer to the subject during the interview, which will help you maintain a more comfortable, conversational distance. You don't want your subject feeling as though he/she has to yell during the interview to be heard.

Comfort 

Being a good documentarian means knowing your subject. Building rapport means building trust, which lends itself to more genuine interviews. So, you should determine how comfortable your subject is with the camera before the interview takes place.

Some people become very nervous and closed off if they sense that the camera is right on top of them. For these people, the camera needs to be a good distance away, so they don't have to think about it being there. For these situations, a longer lens is needed.

For those subjects who are very natural on camera, then you can afford to use a wider lens and bring the camera a little closer.

Remember, lens choice, camera placement, and composition say a lot to the viewer, even if subconsciously, and should be carefully considered. Listen to cinematographer Roger Deakins talk about his philosophy on lens choice and camera placement in this video essay (starting around the 1:32 mark):

How do you film a conversation? Most likely, you're going to block the actors, set up the camera, and do shot/reverse shot. But where do you put the camera? What lens do you use? And how do you cut back and forth?

Have any other tips for aspiring filmmakers on lens choice? Leave your thoughts in the Comments section below.