In both of the photographs above the model (the lovely Jade) is in the same position relative to the background. She's standing on a concrete barrier that separates the parking lot of the Santa Barbara Pier from the walking/running/bicycle path that runs next to it - between the parking lot and the beach. If you look at the plant next to her in both photos you'll see that it's relative position to Jade doesn't move. What is vastly different in both photos is the appearance (size) of the background (Stearn's Wharf - in beautiful Santa Barbara, California) in relation to Jade. This is due to the focal length of the lens. Longer lenses (telephoto - super-telephoto) compress space and make objects look much closer and wider lenses or lenses with a shorter focal length make objects look smaller or father away. This principle is true for VIDEO - FILM - or still photography. ESPECIALLY if you are shooting HD video with a DSLR or any full-sensor chip video device. Focal length relative to the format you are using may apply, but generally speaking the information in this card translates to video and film for the underlying physics (optical) remain constant.
In each instance I made Jade appear the same relative size in the frame to show the dramatic difference that the lens focal length would have on the background behind her. To keep her the same relative size I had to move closer to her (with the shorter focal length lens) that I stood when I shot her photo with the longer focal length lens. Other than changing MY relative distance to the subject - her relative distance to the background did not change.
For this demonstration I chose two of the best portrait lenses ever made - the Nikon (Nikkor) 85mm f/1.4G and the Nikon (Nikkor) 300mm f/2.8GII ED VR - both are the most current version of these lenses featuring Nikon's Nano-Coat <N> lens treatment and featuring Nikon's "Silent Wave Motor" focus systems. Both lenses have fast apertures featuring curved aperture blades (for soft round bokeh), feature extremely crisp optics with little distortion, practically zero color aberration, resulting in stunning portraits. Both are IF (internal focus) PRIME lenses (meaning they are a constant focal length - they do not zoom). There is a significant size and weight difference between these two lenses. The 300mm lens is over a foot long and comes in with a weight of approximately 6.5lbs. The 85mm lens is 4.5" long and weighs 1.5lbs. To most photographers the size and weight difference of these two lenses is the most important factor when reaching for one of the other - but I suggest that these are non-issues when you consider the difference in how they affect the composition of your photo. So why would you select one over the other?
The answer is not as straight forward as one lens has a larger aperture so you could use it with less light in a difficult natural light environment - or that one lens is much smaller and weighs significantly less so it'd be easier to handle. When you look at the photo above and the one below - clearly Jade is the main subject and the focal point of both images. But in one photo the background plays a much larger role - literally - in the composition. Above you can see the groups of students in the sand watching the volleyball games in the background. In the photo below these background subjects barely register - and they don't read as anything important to the subject of the photo; they are simply there. Because of the lens choice I am able to give significance to her backdrop or remove it. It can be a photo that is solely about the subject or it can be about the subject as she relates to a particular backdrop. In this case Jade is a collegiate athlete and sports/outdoor activities are central to who she is as a person.
The focal length of the lens can help you shoot an image that minimizes the background - downplaying its significance to the subject - or it can augment the background and make it a significant part of the narrative of your photo. In the two photos above - the photo shot with the 300mm lens (which brings the group of volleyball players and their spectators closer to Jade) gives her a stronger connection with that group. She is now a person who identifies herself as a more social person. In the photo shot with the 85mm lens minimizes the group's connection to her (by making their presence in the composition small enough to not even be sure what they are besides a dark splotch of color against a large sandy colored splotch) and it gives her a more solitary - alone persona. Her body language in both photos also support this (she is leaning towards the group of volleyball players in the photo where they are more prominent).
A good photographer is always aware of how EVERYTHING will affect their work. Lens selection should be ANYTHING but arbitrary. And the "standard rules" for the use of this or that lens should never apply to the photographer who understands why these rules exist and why they should sometimes be broken. By shooting portraits with a super-telephoto lens you compress distance and space - bringing the background closer to your subject - allowing you to make it a more important part of telling their story. You can also take a photo which is average and make it interesting. In the first examples of this card - look again at how the wharf looms in the background in the image shot with the 300mm lens. The composition of this image frames Jade in an interesting way - the underlying subtext of the photo is that the location (the wharf) is important to her. In the image shot with the 85mm lens the wharf is smaller and not nearly as important in the frame - there's more beach visible and she's holding a beach-themed skateboard. This image conveys the subtext that the beach is more important to Jade. Both lenses allow you to tell a different story about your subject. And so both lenses should be chosen for their ability to help you tell the story in the most effective way. REMEMBER - Accidents are nice - but knowing why a particular photo turned out the way it did - especially after having planned for it to - that's what a pro does.
I have over 25 years of experience as a photo journalist & professional photographer. I have a bachelor's degree in film production & cinematography. I am a Nikon Professional Photographer and use Nikon cameras, lenses, and accessories exclusively.