Fixed Lens vs. Zoom Lens

A prime lens is usually has fixed focal length, that means that the focal length can't be changed at all.   A zoom lens is a variable focal length lens meaning you can turn the lens and change the image size. A common zoom lens would go from 50mm (normal) to 100mm (telephoto)   It's important to note that not all zoom lenses are about magnification.  Some range from 28mm wide to 50mm (normal lens)     

A prime lens is usually has fixed focal length, that means that the focal length can't be changed at all.  

A zoom lens is a variable focal length lens meaning you can turn the lens and change the image size.

A common zoom lens would go from 50mm (normal) to 100mm (telephoto)  

It's important to note that not all zoom lenses are about magnification.  Some range from 28mm wide to 50mm (normal lens) 

 

 

 

PROS OF A ZOOM LENS:

  • Versatility: You do not have to buy multiple lenses to get a variety of shots 
  • Ease: You do not have to change lenses to change focal length
  • Camera move: If you are into a retro look for your film you may want to try a zoom for a camera move (see video below)
  • Cost: Welp! Here's the deal.  You may save money by not having to buy a whole bunch of lenses, but you also have to pay a lot for quality and better optics in variable focal length lenses.  Also, getting a lens that ranges from say 20mm to 200mm will not have good image quality, so you can't get a sharp lens that covers such a wide range of focal lengths.   

Pros of a prime lens

  • Sharper: they are only meant to obtain sharp focus at one focal length, so they create shaper videos and images
  • Cheaper: Again, some people believe that zoom lenses are cheaper because you get a bunch of lenses in one.  Not exactly true, because you have to pay handsomely for "good glass" with a variable focal length lens. 
  • Faster aperture: The aperture is the opening in the lens, and it helps to control exposure.  (A smaller lens opening=less light and a larger opening=more light exposing your chip.)  Most variable focal length lenses do not have larger apertures while fixed focal length lenses tend to open fairly wide.
  • Note: lenses that open to larger apertures like 1.4 are called fast lenses.  

The Digital zoom

My advice would be never to use a digital zoom because all it is doing is magnifying the image and lowering the resolution of your video. If you are filming with your smartphone, it's likely there is no variable focal length on its tiny little lens, and therefore the image is being magnified digitally. A video magnified that way can make it appear noisy and pixelated, so if you aren't using an optical zoom, meaning the lens is creating the magnification, then just move in closer to your subject.