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Alexa with 16mm Ultraprime issue


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#1 Bruce Greene

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Posted 11 September 2015 - 11:52 AM

I recently shot a film with the Alexa and Ultra Prime lenses.

My issue is flare with the 16mm lens. I noticed a flare in the center of the image and tried to flag the lens, but it did not help. I then discovered that the flare is exactly a circle in the center of frame. It's caused by a bright background reflecting off the sensor, back to the rear element of the lens, then back to the sensor as a circle of flare over the cross hairs.

This will be tough to fix in DI I think, but doable.

My question: Is there a lens set that does not exhibit this issue?
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#2 Kenny N Suleimanagich

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Posted 11 September 2015 - 02:06 PM

I wonder if Master Primes would have this happen?
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#3 David Mullen ASC

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Posted 11 September 2015 - 02:17 PM

I used that lens for some shots in "90 Minutes in Heaven" on the Alexa and didn't notice this, maybe I got lucky.
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#4 Bruce Greene

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Posted 11 September 2015 - 06:06 PM

noticed the effect a few times. I'll try to look for an example frame, but it'll take a little while to find in the dailies...
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#5 Tyler Purcell

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Posted 11 September 2015 - 11:42 PM

I have similar problems with my Rokinon lenses and my Blackmagic Pocket camera. There is image refraction happening on the back element of glass. It's hard to see if you aren't looking for it. I've never noticed it on any other camera I've shot with.
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