Quick question about iris and zoom?

[Ryan Mueller]

Can somebody please explain to me why the iris gets smaller as you zoom in with the XL2? I have been noticing lately that on a medium focal length I set the iris to 1.6 (full open), then I zoom in for a tight shot for a shallow DOF and the iris closes down to 3.4 sometimes. As I widen the shot again the iris opens back up to 1.6. I am shooting in full manual with the 20X.

I appologize if this has already been covered, but I haven't come across the subject yet and am very curious as to why this happens.


Thanks in advance,
Ryan

[Greg Boston]

It's a design limitation of the lens. FWIW, that's one advantage of having the 16x manual lens as it can maintain wide open f1.4 at full telephoto. That translates to better sensitivity on full zoom.

-gb-

[Dale Guthormsen]

Just a thought,

Can you not exposure lock, then zoom???

[Richard Hunter]

Originally Posted by Dale Guthormsen

Just a thought,

Can you not exposure lock, then zoom???

Hi Dale. No, it's not really an exposure setting. Even when you try to fix the exposure, the lens physically cannot maintain the widest apertures when you zoom in. It's very common with this type of lens.

Richard