Go Back   Steve's Digicams Forums > Digicam Help > General Discussion

Thread Tools Search this Thread
Old May 27, 2006, 11:01 AM   #1
Senior Member
Join Date: Jan 2005
Posts: 112

Why is it that the large apature / low f stop lenses are so much more expensive? From a lay persons perspective, it doesn't seem like it would be that hard to make the apature open up a little more. Or, is this a marketing deal?

Why does the apature size have to go down (increase f stop) as I zoom on my 18-200mm lens?
stevem1928 is offline   Reply With Quote
Sponsored Links
Old May 27, 2006, 11:04 AM   #2
Senior Member
Boily's Avatar
Join Date: Jul 2005
Posts: 3,704

Because the zoom lens will be faster and sharper!! (I believe)
Boily is offline   Reply With Quote
Old May 27, 2006, 3:53 PM   #3
Senior Member
Join Date: Aug 2002
Posts: 851

A larger aperature requires the lens to be physically larger. More glass, more precision grinding, more coatings, more... Well, you get the idea. And all that means more expensive to produce and hence to buy. So no, it is not all marketing.

To maintain a constant aperature on your zoom lens would result in a MUCH larger and therefor, more expensive, lens. That 18-200 is a consumer lens and most consumers are just not going to pay the price. Take a look at the price, and size, of a constant aperature zoom and you will see what I mean.
amazingthailand is offline   Reply With Quote
Old May 28, 2006, 8:14 AM   #4
Super Moderator
peripatetic's Avatar
Join Date: Nov 2004
Posts: 3,598

The f-stop is quite literally the ratio between the aperture and the focal length.

Think about this - a f1.4 50mm lens needs an aperture of 36mm. That means you need a hole 36mm wide at the inside of the lens to let light through. Add the glass and plastic/metal surround and it has to be physically quite large.

The longer the focal length the worse it gets.

That's why the long lenses have to have such wide front elements.

They are more expensive because you need lots more glass and metal. The manufacturers would love to make their lenses smaller and lighter, but they physically can't.
peripatetic is offline   Reply With Quote

Thread Tools Search this Thread
Search this Thread:

Advanced Search

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off
Trackbacks are Off
Pingbacks are Off
Refbacks are Off

All times are GMT -5. The time now is 5:18 PM.