# Why do I want lower aperture lenses?



## Vespa (Mar 26, 2011)

Why are 2.8 aperture lens so much more expensive than ones with higher numbers? I no this is a better lens but I don't know why. Why are primes so much more than zooms? I hav two zooms now, 18/55 kit lens and a 70/300 and I want to add more to my bag so I am looking for ideas. I shoot with a Nikon d300 and I like to shot a variety of editorial, news, nature, & sports. Please help!


----------



## 480sparky (Mar 26, 2011)

Same reason driving with your high beams makes it easier to see...... there's more light!

Aperture numbers are like golf scores..... the lower the number, the better.  An f/2.8 lens is easier to focus than an f/4 lens.  It allows more light through so the viewfinder image is brighter and crisper and easier to see.

Making lenses with larger apertures is more expensive (more material) and harder to engineer in terms of coma, chomatic abberation and other lens flaws.

This begs the question:  Do you want a larger ("faster") aperture lens, or do you need one?  Depends on what you shoot.  If you're in a lot of low-light situations, then you should consider dropping the coin for a fast lens.  If you're just going to shoot vacation pix, then you can save the scratch for something else.


----------



## ann (Mar 26, 2011)

Not all prime lens cost more than a zoom, some can and that depends on the fstop (how fast) and the quality of the consturction.

Both have a time and place.


----------



## Vinny (Mar 26, 2011)

The lower aperture lenses are usually sharper too than the higher aperture lenses. But there are sharp lenses out there that are with higher apertures, I see you have the 70-300 - if it is the newer version (VR) vs the non VR it is supposed to be a pretty sharp lens. I own it but don't have anything to compare it to and I think it its awesome ... of course I may not think that if I had the 70-200 f2.8, LOL!

Since your shooting with a Nikon take a look at their 50mm 1.8 (~$120) or their 35mm 1.8 (~$200). I do like zooms but their cost is up there for me so I decided to save for a prime and "zoom" with my feet.


----------



## Vespa (Mar 26, 2011)

Thanks for the feedback ladies and gentleman!


----------



## KmH (Mar 27, 2011)

Just to keep things on the up and up.

f/2.8 is a bigger number (and a wider open aperture) than f/4 is, because the number is a fraction. 1/2 of something (f/2) is bigger than 1/4 of something (f/4).

The f is equal to the lens focal length - expressed as 1.

So a lens that has a focal length of 100 mm that is set to f/2 has a lens aperture diameter of 50 mm, or 1/2 of 100 mm. The same lens set to f/4 has a lens opening diameter that is 25 mm across, 1/4 of 100 mm.
A lens that has a 50 mm focal length set to an aperture of f/2 has a aperture opening that is 25 mm across, and at f/4 is only 12.5 mm across.


----------

