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Oily Iris Blades


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#1 Jon Petro

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Posted 14 October 2007 - 12:59 PM

What can be the effects of having oily iris blades in your lenses?

Could it affect the image in any way?

Jon
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#2 Mark Dunn

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Posted 14 October 2007 - 03:04 PM

The blades are lightly lubricated where they are in contact; I can see the oil in one of my lenses. It's not a problem. In still camera lenses meant for viewing at full aperture and stopping-down only during exposure, they might gum up, but cine lenses stay stopped-down, so they're fine.
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#3 Jon Petro

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Posted 14 October 2007 - 06:55 PM

The blades are lightly lubricated where they are in contact; I can see the oil in one of my lenses. It's not a problem. In still camera lenses meant for viewing at full aperture and stopping-down only during exposure, they might gum up, but cine lenses stay stopped-down, so they're fine.


Okay, so I guess oily iris blades are normal for cine lenses. I never noticed before. I was aware that they could be an issue on still picture lenses so I guess that is what I was thinking. As long as it doesn't affect my image I don't care. I was afraid some sort of reflection could occur off the back of the iris blades.

Thanks for the response,

Jon
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#4 chuck colburn

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Posted 15 October 2007 - 11:20 AM

Okay, so I guess oily iris blades are normal for cine lenses. I never noticed before. I was aware that they could be an issue on still picture lenses so I guess that is what I was thinking. As long as it doesn't affect my image I don't care. I was afraid some sort of reflection could occur off the back of the iris blades.

Thanks for the response,

Jon


Oily iris leaves are not normal for ANY lens. If the lubricant begins to dry up or is cold enough the individual leaves can stick to each other and can result in them kinking up and the destruction of the whole assembly. I highly recommend that you have the lens serviced as some lenses have no parts availble for them and would require parts from another lens for repair.

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#5 Mikkie Jo Stevens

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Posted 18 October 2007 - 06:06 PM

but cine lenses stay stopped-down, so they're fine.


UH! The whole point of aperture is to control DOF and cine lenses certainly DO NOT stay stopped down. Oil on blades indicated they were once stuck and have been oiled instead of cleaned. It's bad news. If you have an expensive lens here get it opened up and the apertures cleaned and the dust removed from the elements.

Jo
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#6 Nick Mulder

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Posted 18 October 2007 - 06:49 PM

UH! The whole point of aperture is to control DOF and cine lenses certainly DO NOT stay stopped down.


He means relative to (most) stills lenses where they are usually always open and you have to affect some sort of aperuture preview switch to see the shooting DOF, this and also when the exposure is being taken is when the iris blades if ever are closed - they have to be especially fast to close and open again when you hit the release...

Cine lenses on the other hand never in normal shooting conditions have to acheive the same speeds, and are often left at the last setting inbetween takes, which more often than not is some partial form of closure ...

I wouldn't worry as much as you make out - apart from the possibility of the grease/oil getting into the optics as I have had happen when a lens was dropped, and the long term badness - and yes I suppose the extra internal reflections wont help things either .. but its not a show stopper

Nick
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