UM46 - Sigma 18-35 / 50-100 NO IRIS CONTROL

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mauro.fluehler

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UM46 - Sigma 18-35 / 50-100 NO IRIS CONTROL

PostWed Oct 25, 2017 8:50 pm

Hello people, I have a problem with the IRIS control to my Sigma 18-35 and Sigma 50-100. Sometimes my Ursa Mini 4.6k loses control to the iris. I have no idea why.. Ursa mini and the lenses have the latest firmware. Has anyone an idea why that could be? Thanks..!
Mauro Flühler | film student | switzerland
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Robert Niessner

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Re: UM46 - Sigma 18-35 / 50-100 NO IRIS CONTROL

PostWed Oct 25, 2017 11:07 pm

If memory serves me right, there was a problem with older Sigma 18-35 lenses, which got solved by a firmware update FOR THE LENS (not the camera). For updating Sigma lenses you need a dock from Sigma.

I have the UM46k with firmware 4.2 and a Sigma 18-35 (bought in late 2016). No problems with the iris control so far.
Robert Niessner
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Robert Niessner

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Re: UM46 - Sigma 18-35 / 50-100 NO IRIS CONTROL

PostWed Oct 25, 2017 11:18 pm

Yep, found the lens firmware problem here:
viewtopic.php?f=2&t=50972&start=100#p294704
Robert Niessner
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mauro.fluehler

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Re: UM46 - Sigma 18-35 / 50-100 NO IRIS CONTROL

PostThu Oct 26, 2017 8:22 am

Thanks for your reply. Already checked the firmware of the lenses. So, this can't be the issue..

Anyone else has an idea?
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Jesse Widener

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Re: UM46 - Sigma 18-35 / 50-100 NO IRIS CONTROL

PostMon Nov 13, 2017 6:17 am

I have this same problem and would love a solution. Lens firmware is also up to date for me. In addition to losing iris control, the iris occasionally "jumps" causing a split second burst in exposure which ruins a shot. That is the greatest concern.
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Ryan Payne

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Re: UM46 - Sigma 18-35 / 50-100 NO IRIS CONTROL

PostMon Nov 13, 2017 11:33 am

Maybe it's something to do with how the mount is connecting to the lens.

I know that if I don't have my micro mounted bmpcc speed booster locked down to the cage I can sometimes cause the connection to wiggle and I assume this grinds the pins back n forth. This causes the lens to freak out, change Iris back and forth quickly or stops responding at all. If it happens I need to power down the camera and as such the speed booster down then back on and it's fine. I've yet to have it happen if the booster is bolted down to the support foot. The speed booster sits quite tightly when mounted. Lens to booster has a small wiggle but I haven't managed to force this to happen when the booster is bolted.

This only happened when using the old nifty fifty Canon lens with it's poor plastic ef mount.

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