Lens Diameter

Is there any other benefit to having a wider lens diameter than just allowing

more light into the lens? (eg. 55mm vs 67mm diameters)

 

Thanks.

Ray

A larger lens diameter [for a given focal length] means a faster lens is possible, which will allow you to use faster shutter speeds and which will blur backgrounds more.

 

However sometimes all of the front element isn't used, especially with zoom lenses. A larger front element may *allow* a faster f-stop but doesn't guarantee it. With prime lenses it usually doesn, but not with zooms.

 

For exaple the front element of the 50mm f1.8 lens is pretty small (about 30mm, with a 52mm filter diameter), while the front element of the 17-85mm is much larger (about 51mm) and uses a bigger filter (67mm), even though at the 50mm setting it's much slower (about f5)

Hum interesting question got me thinking . . .

 

1. usually means it is a faster lens. (I know you implied that in your question)

 

2. easier (for me) for manual focussing and manual aperture control.

 

3. easier to brace Hand Held when shooting at slower shutter speeds.

 

4. more stable on a camera pillow (like 3 above).

 

5. more mass when in a press door stop bun fight (seriously).

 

That`s off the top of my head, interested to here other`s opinions.

 

Regards

 

WW

On wide angle lenses, extra large filter sizes help to avoid filter-induced vignetting. A fatter lens barrel leaves more room for the internal mechanics/electronics and to some extent, provides better grip/balance.

You can't get away with anything less than the geometrical aperture at SOME points in the lens, including the front element, although the back end of a telephoto can be smaller than this. Most modern zoom lenses have front elements that are substantially larger than this minimum in order to provide the necessary angular coverage. Skimp on this, and you increase the vignetting at large apertures at the wide end. That's why all the WA zooms have to take a 77mm filter but the 70~200/4 can manage with 67mm. The closest 'match' is probably the 300/4, which requires an aperture of 75mm and takes a 77mm filter.

Other things being equal one consideration is that if you rationalise your lenses to similar filter sizes you don't have to buy multiple sets of filters. Of course, this matters less with digital cameras where you will tend to use fewer filters than you would shooting film (especially B&W)- but polarisers can be expensive in larger diameters.