Lose f-stops when zoomed in?

[Bokes]

Shot a short film this past weekend and was having a strange problem.
Shooting in manual:
Whenever I would zoom in the get focus I was unable to dial certain f-stops.
For instance if I was set to 1.7 on the wide- I would zoom in and the f-stop would change to 2.8 and not let me open back to 1.7 until I zoomed back out.
I would only let me open to 2.4 or OPEN.
Why?
We were shooting manual. We checked several times. (unless we missed something?)

[Barry_Green]

No problem, that's the way these zoom lenses work. F/1.6 is the widest open you can get, but only at full wide angle. At full telephoto the most-open it can be is f/2.8. All the small cameras work the same way.

[mikecentola]

Yeah exactly what Barry said. If you have any experience with photography, you'll notice that most SLR zoom lenses will list multiple apertures such as Canon's 17-85 f/4 - 5.6

The minimum aperture will vary based on the zoom length.

HTH

[Bokes]

I thought that might be the case.
Thanks.