Webpage showing what lense numbers mean

[Platinum]

Is there a website/page that describes what the numbers attributed to lenses mean, and some nice diagrams?

Thanks.

[UKBob]

Dont have any links (am sure others do) but you do understand the difference between F2.8 and F11, right?

[Gemm]

Or do you mean MTF chart??

[poah]

a 17-85 f4-5.6 means the focal length of the lens is 17mm to 85mm. the f4-5.6 refers to the maximum apertureof the lens, in this case f4 @ 17mm and f5.6 @ 85mm. constant aperture lenses just have one number. the other letters generally don't mean much. for canon USM is the fast, silent focus motor, nikons is AF-S, sigma is HSM. these have full time manual focus which means you can focus even after the camera has "locked on" Sigma also have DC, nikon have DX and canon have EFS which are crop camera only lenses in that they have a reducedimage circle to that of full frame (35mm) camera's. on the front of the lens it will usually tell you the filter size too in mm.

[UKBob]

Gemm said:

MTF chart??

MTF?

So many questions

[poah]

UKBob said:

Gemm said:

MTF chart??

MTF?

So many questions

MTF charts show contrast and resolution (sharpness) of lenses. cheap crapy lenses ahve low scores, expensive lenses generally ave high scores

this is a good review

www.luminous-landscape.com/tutorials/understanding-series/understanding-mtf.shtml

[barreti]

poah said:

a 17-85 f4-5.6 means the focal length of the lens is 17mm to 85mm. the f4-5.6 refers to the maximum apertureof the lens, in this case f4 @ 17mm and f5.6 @ 85mm. constant aperture lenses just have one number.

aaah, so THAT explains it. I know its really dim of me after having a 300D for more than a year now but I really didn't know why lenses had F stop ranges on them.
Living and learning

[Platinum]

I didn't word my question very well.

UKBob said:

Dont have any links (am sure others do) but you do understand the difference between F2.8 and F11, right?

Yup, I understand the aperture ok. Its the focal lengths and how they determine the size/zoom of an image; (if that is correct.)

[tank slapper]

There is a reasonable explanation here

Edited by tank slapper on Monday 25th September 14:38

[Platinum]

tank slapper said:

There is a reasonable explanation here

Edited by tank slapper on Monday 25th September 14:38

Brilliant, Thanks.