Lens Diameter Benefits?

R8JimBob88

R8JimBob88

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James Stockton
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Just a random question that popped into my head about 30 seconds ago....

What are the benefits of having a lens with a larger diamater of glass? For ecample, the Nikkor 18-55mm has a diameter of 52mm but the 18-70mm has a diameter of 67mm?

Sorry for the randomness, especially on a Monday! :)
 
simple sums old chap
55 mm lens f/2 needs 27.5 mm max aperture size
allow space for gubbins (in your case 24.5 mm)
70 mm lens f/2 needs 35 mm max aperture size
allow space for gubbins (in your case 32mm)

the gubbins includes focus motor, lens body etc

500 mm lens f/2 needs 250 mm just for the aperture
by the time you add all the gubbins you've got a big lens diameter (as well as length)

numbers are examples, of course, but the principal is right(ish)
 
The lens construction, number of elements to make up the focal length, maximum aperture value, IS (or not) determine the diameter of the lens.

The lens in my avatar is a 400/2.8 IS.
 
Slapo said:
It's an indicator for some police members that look for suspicious looking people. ;)
Click to expand...


Yup the bigger the number, the more sticks of explosive you can fit inside.
 
Heh, the wider the range you have the more filters [or adaptor rings] you have to carry. The bigger the filters the more they cost too :(
 
R8JimBob88 said:
Yep, just priced up some filters for my new lens :(
Click to expand...

Have you considered the Cokin [or Kood] filter system? You buy the holder and slide filters then the right diameter adaptor for the lens. £3-5 a ring but means you can use the same filters on a range of lenses.
 
I have some of the cokin grads etc but prefer the screw in type for polarisers etc. Going to get a ND10 too! :D
 
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