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-   -   No Open Iris In Wide-Photo? (https://www.dvinfo.net/forum/sony-vx2100-pd170-pdx10-companion/92058-no-open-iris-wide-photo.html)

Aviv Hallale April 21st, 2007 05:44 PM

No Open Iris In Wide-Photo?
 
I was shooting a band today, one shot was in telephoto with the iris open and a gain of 3db. When I moved to widephoto, I noticed the iris automatically went down to F2, but the 3db was still displayed. However, in widephoto, I could manually open the iris again. The adjustments were on manual, autolock in the middle position.

I understand that this isn't a defect, but what is the principle behind closing the lens during a wideshot? Is it to deepen the depth of field?

Bob Hart April 21st, 2007 09:20 PM

This is a normal optical characteristic of some zoom lenses. Other zoom lenses are designed to perform with the same aperture value through the whole zoom range.

Tom Hardwick May 14th, 2007 03:12 AM

It sounds to me Aviv that your shots at full telephoto were under-exposed by half a stop. You were shooting wide open (f/2.4) at +3dB of gain up? Then you pulled back to wide-angle and the camera chose f/2 at the same gain setting?

That would suggest to me that it wanted f/2 in the first place, and your zoom isn't that fast at the 72 mm end. It's nothing at all to do with D of F and all to do with the fact that the max aperture of your zoom varies from f/1.6 to f/2.4 depending on what focal length you're shooting at. All perfectly normal.

tom.


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