Focus - aperature - ZOOMING?

[Dyrseve989]

just a quik question to those arri SR-II users, Say when I use a 50mm zoom lens, and I zoom from widest shot, all the way to 50mm, would I have to gradually adjust the aperature open as I zoom in? or is it very unnoticeable......

Note: I am shooting in an enviorment where medium grey scale is at an aperature of 5.6

-Matt-

[Dyrseve989]

......umm....ill explain again, maybe im not being logical about this, the more you zoom, the more light you lose, correct? so If I am using a zoom lens and have a shot where I am using the full length of the zoom, won't I be losing (most likely a small amount) of light? enough that will make a difference from widest point A to zoomed in, point B?

[kplo]

Zoom lenses for motion picture cameras generally have a constant aperture at all focal lengths. If your shooting at 5.6, it will remain 5.6 from wide to tele.
Hope this helps.
Ken
The Screen Skins guy

[taubkin]

It's not that logic.

Some zooms have different maximum apperture for different focal lenghts, mostly photographic lenses. Movie lenses, as Kplo said, keep a constant f-stop. What would happen is that IF you are shooting wide (the place your lens is more luminous) AND wide open (let's say your lense is 2.8 in the wide end), when you zoom in, you will see the light going away. However, if you close down to your maximum apperture at full tele (let's say it's 4.0), you lens will keep it when you zoom out. So if you are not shooting wide open you are safe, and if you are using a movie lens, (I believe the Zeiss 8-50mm, right?), you are safe.

BTW, no, you can't correct apperture while you zoom, that would look bad...

[Dyrseve989]

ohh, I don't know why I was thinking I'd loose light, maybe photography?