Camera lens's

[matt_london]

<PRE>If a camera has a 'fast' lens what does that mean and why are some lens's thousands of pounds. What difference is there between a really expensive one and one that came with the camera?</PRE>

[WoWo]

They are simply better quality, much like the difference between an Escort and Ferrari. Better build quality the ability to take clearer pictures etc etc.

My dad has a �2000 digital camera and I have a �200 both 8 Mega Pixels but the difference with his (at least most of it) is the lens.

[gary baldy]

A fast lens is one that can achive a very wide apeture and therefore lets in more light allowing for faster exposures - very useful in zoom lenses and for low light conditions.
They are popular with sports photographers and paparazzi.

[Ralph]

A fast lens can open to a large aperture (f1.0). This means that the time needed for a proper exposure is very short which is good for action photos. But a big aperture means that the lens needs big pieces of glass to be cut and polished which is expensive. The lenses also include things like environmental seals so that the professionals who have to sit in the rain at a football match to get photos don't ruin the expensive kit that only really they can afford!

[Ralph]

Beaten to it! Doh....... Nice one gary.

[oakleydoaky]

smaller number, bigger hole = more light.

[gary baldy]

An environmental seal?
Are they like Green Penguins or anti nuclear Polar Bears?

[matt_london]

<PRE>what sort of difference in size are we talking about when you say that the aperture opens larger? Any idea what the diameter of the 'hole' would be? </PRE>

[gary baldy]

It depends on the 'size' of the lens. Its all relative to the diameter of the lens. Its isnt measured on diameter its measured on relative size compared to the lens.
Click on some of the 'blue' ads next to this post and compare the different lenses. The lower the 'f' number the faster the lens - and usually the higher the price.