cinematography fixed aperture zoom

[nivek535]

hi there ! (an inactive newbie here!)
I have a question about zooming with fixed aperture.

i know that the widest aperture for zoom lenses (most) are fixed by the focal length you're at,
but for example, if i use a 18-55 3.5-5.6 lens and use f5.6,
why cant i zoom from 18 to 55 keeping it fixed at 5.6?
my camera is D3200.

thanks !

 

[WalterB]

at 5.6 it should be possible. Just set it to 5.6.

At 3.5 (or anything below 5.6) it is mpossible.

 

[nivek535]

hey thanks for the reply, but that is exactly my question !
Why is it not working ?

I am on M, video mode.
zoomed out (18mm), set aperture to F/5.6.
when i zoom in to 55mm, the aperture changes to F/9.x or something .....

 

[WalterB]

That's weird.
I'm not familiair with Nikon, but maybe someone else knows what could be the problem...

 

[nivek535]

i figured out a solution!
using aperture priority and locking exposure

 

[gpforet]

Might want to ensure that the camera is not changing your shutter speed or ISO. Typically aperture priority will auto adjust shutter or IS0 to keep exposure constant.
.

i figured out a solution!
using aperture priority and locking exposure

 

[nivek535]

Might want to ensure that the camera is not changing your shutter speed or ISO. Typically aperture priority will auto adjust shutter or IS0 to keep exposure constant.
.

oh yea, i had to point the camera around until i had the right shutterspeed before locking it