Fast lenses July 2009
What is a “fast” lens anyway?
Applied to a lens, the term “fast” refers to faster shutter speeds made possible by the superior light gathering power of a lens.
A fast lens is always larger heavier and more expensive than a slower one. For example, a 50mm f/1.2 lens might cost $1600 compared to $300 for a 50mm f/1.4 lens and $100 for a 50/1.8.
Each f-stop represents a full shutter speed. So an f/1.4 lens allow one faster shutter speed than an f/2 lens, and two faster shutter speeds than an f/2.8 lens. That’s a very big deal at dusk, or indoors.
Most consumer zooms are in the f/3.5 - f/5.6 range, meaning that they lose 2-3 shutter speeds, a huge difference leading to blurred images when the light levels drop (which requires a lower shutter speed).
Examples
| Focal length range (for 35mm format) |
Max Aperture |
|---|---|
| 12mm - 21mm | f/2.8 |
| 22mm - 35mm | f/1.4, f/2 |
| 50m | f/1.2, f/1.4 |
| 85mm | f/1.2, f/1.4 |
| 90mm | f/2 |
| 100mm, 135mm | f/2 |
| 180mm, 200mm | f/2, f/2.8 |
| 300mm | f/2.8 |
| 400mm | f/2.8, f/4 |
| 500mm | f/4 |
| 800mm | f/5.6 |
See also
- Brand-new Blur
- diglloyd’s Advanced Photography — in particular, focus shift with fast lenses, reviews of various fast lenses.
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