
My first professional photo award came the month after I bought a 300mm lens. Although it was a slow manual lens (f/4.5), I felt like my camera suddenly grew wings and could record emotions I was unable to capture before.
During most of my newspaper career, I carried only three lenses: 24mm, 180mm and 300mm. If I had a shoot that required something like an 85mm, I borrowed a lens.
Whether fixed/prime or zoom, telephoto lenses magnify reality, allowing you to focus on subtle emotions easily missed with a 50mm lens.
Long lenses compress and condense information, bringing faraway backgrounds closer. They allow me to see more deeply into the faces and eyes of people, and eliminate unwanted backgrounds.
A long lens also allows you to quietly incorporate subtle color accents in front of or behind your primary subject without stealing the show.
Here are tips to consider regarding telephoto lenses:

Pay the price. Avoid cheap 50-300mm f/5.6 or f/8 lenses. They are not practical unless you photograph only in broad daylight. If shooting in low light, the difference between f/2.8 and f/4 can be the difference between success and failure.
Well-made lenses are expensive, equal to or greater than the cost of a camera body. A Nikkor 300mm f/4 lens sells for $600 to $1,000. A 300 f/2.8 (one more aperture opening) is $3,500 to $5,000.
Go to a camera store and handle the item to see if it is what you really want. Things often look great online, but feel different in your hands.
Brace yourself. Tripods can be awkward. A lot of photographers—especially those who shoot action sports—use monopods to help stabilize heavy lenses.
If hand-holding a long lens, brace yourself, as if using a rifle. That helps minimize camera/lens movement. A telephoto lens magnifies small movements.
If you don’t use a sturdy base, remember the “rule” of using a shutter speed equal to—and preferably twice that—of the focal length of your lens. For instance, if using a 300mm lens, your shutter speed should be at least 1/500th of a second to minimize camera shake.
I am still a medium to long lens guy. A 180mm lens is my favorite portrait lens. I like the compression, the lack of competing backgrounds, the feel a telephoto lens produces.
At 68, with a tender back, a bad right shoulder and a neck worn from five decades of carrying cameras, it’s tougher for me to use long lenses. That said, I am stubborn enough to endure the pain to capture those faces and moments I want to share.