Lens speeds

[BillH2]

I am confused (obviously) about what it means when it says an F value of 4.0 or faster. What would be faster 2.8 or 5.6 ? Do they mean the lenses that has a low end of 5.6 is slower then one with a low end 2.8 or what ? HELP

[steven]

A faster lens is capable of have a larger apature.
Larger apature is smaller f stop numbers.
So faster than f/4.0 would mean any f stop less than 4.0.

[BillH2]

Thanks.

[robertwgross]

Theoretically, an f/2.8 aperture isn't any faster than f/4, per se. It is just that f/2.8 allows you to use a faster shutter speed than f/4 would, so f/2.8 is informally called "faster".

---Bob Gross---

[PacAce]

Theoretically, an f/2.8 aperture isn't any faster than f/4, per se. It is just that f/2.8 allows you to use a faster shutter speed than f/4 would, so f/2.8 is informally called "faster".

---Bob Gross---
Hmm, let's see. An f/2.8 lens costs more than an f/4 lens, everything else being equal so you run out of money faster when you buy the f/2.8 lens than when you buy the f/4 lens.

The f/2.8 lens is heavier than the f/4 lens, with everything else being equal, so you get tired faster lugging the f/2.8 lens around than you would with the f/4 lens.

Yup, I would definitely have to say that the f/2.8 lens is faster than the f/4 lens. No doubt about that. :lol: :mrgreen:

[Jesper]

When you talk about lenses, "faster" doesn't have anything to do with autofocus speed or anything like that - it refers to the shutter speed. When you use a larger aperture (a smaller f-stop number), you can use a faster shutter speed.

[PhotosGuy]

Hmm, let's see. An f/2.8 lens costs more than an f/4 lens, everything else being equal so you run out of money faster when you buy the f/2.8 lens than when you buy the f/4 lens.

The f/2.8 lens is heavier than the f/4 lens, with everything else being equal, so you get tired faster lugging the f/2.8 lens around than you would with the f/4 lens.
:D:D:D
The older I get, the closer I get to f-60! ;)

[CyberDyneSystems]

:D:D:D
The older I get, the closer I get to f-60! ;)


This actually makes it all more understandable,.

...because clearly at f/18 we were much faster than at f/60 .... ;)