Fast lens for the nikon d5100?
I need fast focus speeds.
any ideas?
Most dslr lenses by either Nikon or Canon are very fast at focus. If you mean fast as in aperture, I recommend the 50mm f/1.8.
Fast/large aperture or fast autofocus? What do you plan on shooting? The 200 f2 is a good balance of large aperture and fast autofocus.
I disagree with AWBoater, a lot of Sigma, Tokina and Tamron lenses are very fast to focus and they're much cheaper than Nikon's own brand lenses. If you're not a professional photographer then you won't miss the minor (and I really do mean minor) differences in focus speed.
When you say "fast lenses" it is generally in reference to aperture (as you may have guessed from everyone's replies). If you're looking for fast aperture lenses the 50mm F/1.8, 85mm F/1.8 and 35mm F/1.8 lenses are very good. They're also very fast to focus due to their fast apertures. Lenses with wider maximum apertures are almost always faster to focus than darker/slower aperture lenses due to the fact that they let in more light.
For fast focusing lenses I would never recommend anything below F/2.8 if you want to be safe. However, there are indeed exceptions - especially in the line of professional lenses such as a 600mm F/4.
Fast, affordable lenses I know of would be the 3 primes I mentioned earlier (35mm, 50mm, 85mm) and the Sigma 70-200mm F/2.8, Tamron 17-50mm F/2.8 and Tokina 11-16mm F/2.8 to name a few.
Stay with Nikon AF-S lenses. Their focus motors are typically faster than those by 3rd party lens makers.
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Stay with Nikon AF-S lenses. Their focus motors are typically faster than those by 3rd party lens makers.
I have an AF lens (external focus motor) that focuses faster than an "equivalent" Sigma lens with a dedicated motor (AF-S).
The reason Sigma and Tamron are cheaper is that they are not as good. You get what you pay for, and this is true in photo equipment too.
Your camera body in combination with lens determines af speed. D5100 doesn't have as good as d7000 af system.
If you are referring to fast lens that will allow a lot of light in, then the nikon 35mm 1.8g dx is the best bang to the buck.
You should look at Nikon AF-S lenses which are additionally designated with IF or IF-ED, this indicates a ring-type ultrasonic (silent wave motor) which is the fastest type of focus motor.
If you want accurate focusing, you will need to look at the professional f2.8 zoom lenses, or the professional grade prime lenses.