Zoom lens f-stop?

[Konstabel]

How does the f-stop vary when using a zoom lens?

ex:18-55 f3.5-5.6
Does that mean the f-stop is 3.5 at 18mm zoom and 5.6 at 55mm?

[tim11]

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Does that mean the f-stop is 3.5 at 18mm zoom and 5.6 at 55mm?

Yes. And everything else in between.

[David Metsky]

ex:18-55 f3.5-5.6
Does that mean the f-stop is 3.5 at 18mm zoom and 5.6 at 55mm?
It means the maximum f/stop at 18mm is 3.5 and at 55mm it's 5.6.

[D Thompson]

Yes. And everything else in between.

It means the maximum f/stop at 18mm is 3.5 and at 55mm it's 5.6.
Unless you are Razr! :rolleyes:

[Konstabel]

So I cannot manually set the f-stop to say 3.5 at 55mm focus and vice versa?

[TheWengler]

You can set it to 5.6 at 18mm, but not the other way around. It's the MAX aperture.

[tim11]

Unless you are Razr! :rolleyes:
Yeah I rememeber the thread. :D

[tim11]

F/5.6 is MAX aperture at full zoom.
F/3.5 is MAX aperture at wide. You can also use smaller aperture (larger number) at wide to whatever the smallest aperture of the lens; normally F/22.
At full zoom the widest Aperture is F/5.6 and impossible to set it to F/3.5, but you can use any smaller apertures possible offered by that lens.
I hope that's clear.