Why you have fast lenses

Why, I am often asked, do you use prime (non-zoom) lenses? And why such fast (low f-number) lenses?

Consider this, a student today at f/1.2:

If you look at that full size, you will see how wonderfully sharp it is, and what incredibly shallow depth of field it has. So why do I have fast lenses?

  1. They are crazy sharp, and I like crazy sharp.
  2. They are consistent (zooming, on the other hand, makes every picture an adventure in different depth-of-field, acceptable slowest shutter speed, etc).
  3. They give me blurry backgrounds if I want (see the picture).
  4. They allow me to use a fast shutter speed. If I shoot in a living room at 400 ISO at f/1.4, I can use maybe 1/250th second. But if my lens was an f/2.8 lens, I would need to use 1/60th second (or I would have to raise the ISO). And with an f/5.6 kit lens (brrr), I would have to shoot at 1/15th second!

That is why I use fast prime lenses. And if I were you, I would get at least a 50mm f/1.8 or even f/1.4 lens.


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