Lens Width - Does it make a difference?

PopeBuckfastXVI

Hi All,

I've been through the FAQ on lenses and it's doesn't answer my Q (which I suppose is not FA!).

Does the width of a lens make any difference?

So if you have a 50mm f/5.6 at 52mm width and a 50mm f/5.6 at 67mm width the 67mm one is obviously way chunkier and way more expensive.

What advantages does the larger width give you? Does it let more light in, or is it better optics, can anyone explain why it's better than a 52mm kit lens?

Thanks all!

fleet

Me thinks you have a little reading to do!
Don't worry, everyone had to at one stage.

Basically a lens has two numbers that you should concern yourself with.
The "lenght" and the aperture.

Length is basically how "zoomed" in or out the resulting image presented to the sensor is. They say 50mm is what normal human eyes percieve as normal zoom. The smaller the number the more stuff appears in the picture, the bigger the number the further away you can get a good pic of something small.

Aperture is how big the hole letting the light throught the lens is. The wider the better (you can always close it down) but also the heavier as more glass is needed.

helios

I think what he is refering to is the physical diameter of the lens...

fleet

Oh wait... having read your question again I think I know what you mean by "50mm f/5.6 at 52mm width and a 50mm f/5.6 at 67mm width".

This is the filter width, basically the width of any filters or lens caps you want to screw on to the front of the lens.

And no, the filter width is not important in choosing a lens, it's loosely related to the aperture (the more glass in the lens the fatter it's going to be, the fatter the lens the bigger the filter).

fleet

helios wrote: »

I think what he is refering to is the physical diameter of the lens...

Just got that. See above.

kgiller

Thats not what he's saying. He's asking what the difference in the diametre of the front of the lens itself is, not the aperture size or focal length.

I googled it and didnt find anything conclusive on the subject. Personally im not sure. All i know is that in general, the more expensive lenses seem to have larger front element diameters. Possibly because it allows for larger apertures? Cant realy help you, have a read around.

PopeBuckfastXVI

Thanks fleet... I'm cool with focal length and aperture, I'm talking about a lens that takes a wider filter... so some lenses take a 52mm filter (mine do) and some take larger, even though the aperture is the same on both.

I'm wondering what the difference is between them?

Like if you had a similar spec'd lens (or lenses) that had the same aperture range, what's the difference

so if you look at this 18-55 f/3.5-5.6 and this 55-200 f/4-5.6 both of which take a 52mm filter
http://imaging.nikon.com/products/imaging/lineup/lens/af/dx/af-s_dx_zoom18-55mmf_35-56g_ed_2/index.htm
http://imaging.nikon.com/products/imaging/lineup/lens/af/dx/af-s_dx_zoom55-200mmf_4-56g_ed/index.htm

would you notice any difference in the 18-135 range in this 18-135 f/3.5-5.6 which takes a 67mm filter?
http://imaging.nikon.com/products/imaging/lineup/lens/af/dx/af-s_dx_zoom18-135mmf_35-56g_ed/index.htm

Or is there no difference and it's just wider to accommodate a longer zoom range inside?

Sorry for the confusion!

Edit:
Just saw the other replies while I was putting this together... I'm guessing it's just a manufacturing thing and it doesn't actually make any difference to the quality of the picture?

sheesh

PopeBuckfastXVI wrote: »

Hi All,

I've been through the FAQ on lenses and it's doesn't answer my Q (which I suppose is not FA!).

Does the width of a lens make any difference?

So if you have a 50mm f/5.6 at 52mm width and a 50mm f/5.6 at 67mm width the 67mm one is obviously way chunkier and way more expensive.

What advantages does the larger width give you? Does it let more light in, or is it better optics, can anyone explain why it's better than a 52mm kit lens?

Thanks all!

it might have an effect on depth of focus a wider lens means that the curve of the glass might might be less. this means that with the aperature wide open the range of the image in focus would be larger (I think) so for low light conditions you would not have one part of the image in focus with the rest out of focus.

so that might be it

I might have got this backwards and it means that the focusing is even sharper. see how big the pro sport photographer lenses are. They need to be able to get the player in focus and everything behind blurry
it also might mean less optical abberation around the edges with a flatter lens

Paulw

Probably to do with the quality of the glass and the amount of light and detail that needs to be allowed in.

I'm not sure that I've seen the same lens in different filter sizes though.

Most of my lenses are 77mm (24-70, 70-200mm), but I've a 16-35mm f/2.8 which is 82mm. I gather this is because of the wider focal length. Of course, the large primes have very large glass (no front end filters though).

fleet

PopeBuckfastXVI wrote: »

Edit:
Just saw the other replies while I was putting this together... I'm guessing it's just a manufacturing thing and it doesn't actually make any difference to the quality of the picture?

It makes bog all difference what the filter width is unless you have existing filters or lenses and you need them all to be compatible.

Just to confuse matters I'll throw in that some filters can be coarse or fine theaded!

Ignore the filter size, it's not nearly as important as other lens metrics (focal length, aperture and sharpness etc).

See the lens tests on www.photozone.de

nilhg

The f number is a ratio, so there is a direct relationship between the focal lenght and the aperture. since the aperture can't be bigger than the outside diameter of the lens there is also a direct relationship between these two.

As an example a 100 mm lens at f has an aperture size of 50mm so the diameter of the lens has to be big enough to accommodate this and all the other necessary parts.

I know I haven't explained this well but you should get the jist of it.

PopeBuckfastXVI

Thanks for the replies all... it's as I suspected... no difference

ThOnda

The difference is in quality of the lens. If there is bigger tollerance during production, there is bigger diameter of the lens, and for optical purposes is being use only the part in the middle with less distortion.

It has nothing to do with optical features of the lens, just the quality of the light transformation (distortion, moire, vignetting).

More likely the better quality lens will have smaller diameter. And will let you save some money when buying filters.

petercox

The filter ring size on a lens should have no bearing on the purchase decision. It is what it is and is determined by how the lens is manufactured.

The only important numbers are focal length and maximum aperture, with minimum focus distance a possible third consideration.

Cheers,
Peter

ThOnda

And maybe even minimal aperture if you are into landscape photography. I've seen aperture 32 and 64 in use. And the pictures were not "too soft". Strange, but nice.

petercox

Thonda -
Typically minimum aperture is tied to maximum aperture (so a lens with a wide maximum aperture will also have a reasonably wide minimum), and telephoto lenses have smaller minimum apertures than wide-angles.

Wide angle lenses better depth of field for the same aperture than telephotos. f/22 on my Canon 24-70mm gives me more than enough depth of field for any landscape application I'd care to use. Hence I don't feel any pain when I can't stop down to f/64

Cheers,
Peter

ThOnda

It was advantage of old russian lenses for Kiev - another their copy of Haselblad. Wonderful lens and camera. And wide as hell!

But back on topic - as far as I remember, the size of the last(first) lens mostly increases with lower price of the whole lens (= the optical quality decreases as well). I take it as a general rule for myself. 52 mm is max. on all my (two) lenses.