Nikon 50mm f/1.8D AF Nikkor Lens

[Britta G]

I bought this lens and have really loved it. The only thing i'm confused about is it's supposed to be a faster lens, and it's supposed to be good in low light, which it is seperately. So in low light still pictures are amazing, and outside it is super fast. But when combining low light and speed, it doesn't seem to be as fast as my kit lens Nikon 50mm f/1.8D AF Nikkor Lens in low light. I know that it indoors the light is lower so I can't bump up my shutter speed as high as I can outdoors without bumping up my ISO, but I just thought it was weird that the kit lens on the same settings is a little faster than the new lens. Is this normal? I'm within my return period on the lens, so I'm wondering if I got a defective one or if this is supposed to happen. Also I just the Nikon D90!

 

[Sw1tchFX]

AF might be, but that's not what's meant by a "fast" lens.

 

[myfotoguy]

Your kit lens is likely AF-S which generally focuses quicker than a screw-drive lens. Is that what you are noticing, the focusing speed?

In low light, with a larger aperture there are times the 50mm D will focus quicker because more light is getting to the focus sensor helping it to acquire focus. But in situations where there is enough light for both lenses to accurately focus an AF-S lens is usually a little faster.

Congrats on getting the D90!

 

[markie]

So AF-S 50mm f/1.4G or AF 50mm f/1.4D is better? or is it a different story?

 

[KmH]

Different story.

Both AF lenses have finer focus gears, or more gear teeth per inch, so manual focusing is more precise.

 

[whiplash23]

I may be dead wrong, but calling a lens "fast" has nothing to do with auto focus speed. The term simply implies that you can use large apertures, thus allowing a faster shutter speed in any given situation.

For instance, a lens that has a max aperture at f5 may require a shutter speed of 1/30s to expose correctly in a particular situation. A lens with a max aperture of f1.8 would allow a much faster shutter speed in the same situation if you are willing to use the larger apertures. I am not versed enough to do the math, but I bet it would be ~1/200s or faster at f1.8.