VernC Loc: NC, 25 miles NE of Charlotte

I often see the words 'prime lens', what is the real meaning of prime lens? Its not clear to me.

ecobin Loc: Paoli, PA

Very simply, it's a lens with only one focal length - no zoom capability. Primes are typically sharper than zoom lenses which is why they are desirable.

BebuLamar

Today it generally means a lens of fixed focal length instead of a zoom lens.
https://en.wikipedia.org/wiki/Prime_lens

LFingar Loc: Claverack, NY

Primes are also faster, as a rule. Some as fast as f/1, although f/1.2 to f/2 are more common. With today's newer zooms, such as Canon's EF 70-200 f/2.8 L II, sharpness isn't as much of a factor as it used to be.

rmorrison1116 Loc: Near Valley Forge, Pennsylvania

A lens divisible by itself and one 8^)

Armadillo Loc: Ventura, CA

Vern,

In simple terms. A “Prime” lens has a single focal length, 55mm, 200mm, or 300mm. Where a Zoom lens has a variable focal length, 55mm – 100mm, 75mm – 300mm, etc.

In more complex terms. With a prime lens if you need to get closer to your target (bird, deer, etc.) you must zoom with your feet and take the chance of chasing the target away. With a Zoom lens you adjust the zoom ring on the barrel of the lens to bring the target closer to the camera sensor.

The trade-offs. With Prime lenses you either walk closer to the target, or change to a different focal length lens. You carry a photo bag with various lenses to interchange as the need arises. With a Zoom lens you carry two to three lenses to cover the greater majority of your target range in distance. With a Zoom lens you sacrifice image quality near the minimum and maximum of it range.

Image Quality problem.
With a Prime lens the manufacturer calibrates the lens to the camera body it is designed to be used on. Since there is only one focal length on a Prime lens the calibration is for that specific length.
With a Zoom lens you have multiple lens elements and lens groups moving as the zoom ring is adjusted. When the lens groups move the calibration changes. The lens manufacturer calibrates the lens at its mid-range, adds corrective lens elements for calibration, and usually gets good image quality throughout 80% of its range.

If you are thinking about a Zoom lens you need to understand its advantages, and shortcomings before you plunk down several hundred dollars.

Michael G

rbfanman

Prime lenses have one focal length, and tend to be sharper, and have wider apertures (smaller f/numbers), than variable focal length zoom lenses. Zooms tend to have 'softer' (blurrier) focus.

Math78 Loc: Scottsdale, AZ

Here's an essay from Ken Rockwell on why you might want to use primes.
http://www.kenrockwell.com/tech/fixed-lenses-take-better-pictures.htm

SteveR Loc: Michigan

A prime lens is like prime steak. They're really, really good.

PixelStan77 Loc: Vermont/Chicago

A Normal prime lens is a 50MM lens. It is a lens that does not have a ZOOM (Variable) focal length capability.

Peterff Loc: O'er The Hills and Far Away, in Themyscira.

I take issue with the specification of a partcular focal length in the definition. I can understand why you cite 50mm, but that is only for the 35mm format if you are considering 'normal perspective' which does not have to be part of the 'prime' definition so far as I know.

Is my Canon FDn 135mm f/2.0 (adapted to EF mount) not a prime lens?

Gene51 Loc: Yonkers, NY, now in LSD (LowerSlowerDelaware)

Where did you get the information about prime vs zoom and mfgr calibration? I am not disputing this, but I'd love the read the entire article. Thanks!

johneccles Loc: Leyland UK

I have Panasonic 20 mm prime lens on my Olympus M43 camera.
This lens has a maximum aperture of F1.7, it is very sharp through the range and is excellent in low light situations.
The 20mm is equivalent to 40mm on 35mm camera so is ideal for most types of photography, so it is permanently mounted on my camera.

jerryc41 Loc: Catskill Mts of NY

Coincidence - I just read an article in Pop Photo about that last night - primes, zooms, advantages, disadvantages, etc. Theoretically, a prime give you a better image. On the other hand, modern zooms give excellent results with infinite focal length adjustments.

billnikon Loc: Pennsylvania/Ohio/Florida/Maui/Oregon/Vermont

Typically is the operative word here. Some modern zooms are very sharp, for example, Nikon 16-35 F4, Sony Ziess 24-70 2.8. I am sure there are many, many more examples to bring forward. How about the Nikon 14-24.