problem with aperture value when i zoom ?
 

Hi! In video mode When I zoom with my 15-85mm the aperture value changes automatically (exposition ?) ... how to avoid it or disable this function !
Because of that i can' t zoom and make video without light changing !

Thanks !
Daniel

Daniel,

The 15-85mm is a variable aperture lens. As you zoom it HAS to adjust the aperture accordingly due to the design of the lens. The way around this is to purchase a fixed aperture lens (it will say something like "f2.8" rather than "f3.5-5.6").

Dan - the aperture value only changes automatically if you're shooting at full wide and max aperture. Try it the other way around - shoot at full tele and max aperture - then zoom to full wide - you'll see that the aperture doesn't change.

Craig's right, you need to buy a fixed aperture zoom lens (usually a lot dearer than the vari-aperture lens you've got)

tom.

Weeell... You don't NEED to...

he needs to if he wants to (quote) 'make video without light changing'.

I understand now !
I must to purchase a fixed aperture lens : maybe the 50mm f1.4 or 1.8 !
Thanks a lot for all of yours !

Daniel

Well you'll find it difficult to find a fixed aperture lens, but I know what you mean.

No - you want a constant maximum aperture zoom. Yours is probably 15 - 85 mm f/2.8 to f/5.6, something like that. What you want (what we all want) is a 15 - 85 mm lens that has a maximum aperture of f/2.8 throughout the zoom range.

tom.