Why are faster lenses expensive?

[pgowder]

Why does it cost SO much more to make a lens f2.8 as opposed to f3.5 ro f4?

Thanks!

[Speed]

Why does it cost SO much more to make a lens f2.8 as opposed to f3.5 ro f4?

Thanks!

Pure size is part of it. A faster lens is a bigger lens, with larger glass elements. The larger a lens, the more expensive it is. Also, the larger the lens, the more exacting you have to be in the manufactuering process.

Also, the faster lenses, especially f2.8 and f1.4, are usually higher quality lenses. They are made to tighter specs and have advanced multicoatings on the lenses to reduce glare and reflections, as well as improve color and contrast.

You may also have noticed that the faster lenses are larger and heavier. Goes with the territory.

Personally, I love fast lenses, and if I had the money, I wouldn't have anything but f2.8's and faster!

[another view]

Two other things - they're built heavier (more metal, less plastic) and I'd bet that they make a lot less "fast glass" than slower lenses, which drives the price up.

[92135011]

and exotic glass for higher refractive index (remember more elements means less light)
and the use of aspherical elements to correct for the aberations
the list goes on and on

[Lionheart]

Why does it cost SO much more to make a lens f2.8 as opposed to f3.5 ro f4?

Thanks!

The glass they use in these lenses is also different, higher quality, and harder to manufacture and because of the higher attrition rate in selecting glass that meets the tighter standards at larger sizes to achieve the faster apertures, you end up paying more. And the list goes on...
BUT....they're worth it. I tried to live with the 28-135 f3.5-5.6 IS USM as a fill in lens after my 28-70 f2.8L and 70-200 f2.8L zooms were stolen 3 years ago, but it just wasn't the same crisp, contrasty images that I was getting on my pro zooms. So I gave myself a hefty Christmas present 2 Yuletides ago and got the 20 f2.8, 50 f1.4, 85 f1.8, 135 f2L, 28-70 f2.8L, 70-200 f2.8L IS, and both the 1.4x and 2x extender II's. Now, I'm happy again
They're worth every penny.