aperture

[gundy74]

i was just wondering why the aperture on zoom lenses is reduced when zoomed.

 

[Big Mike]

The actual aperture isn't really reduced...but the F number is. The F number is a ratio of the focal length and the diameter of the aperture. So as you increase the focal length but don't increase the size of the aperture...then the F number changes.

It's a lot more expensive to make and design a lens that allows the aperture to increase in size as it zooms out...so for cheaper lenses...they make the aperture able to open to a certain size...and that's the maximum for both the short end and the long end of the zoom.

Does that make sense?

 

[gundy74]

yes and thank you