Thread: Scratch on the filter

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  1. #1 Scratch on the filter 
    Senior Member david evans's Avatar
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    Hi guys,

    I dropped my IR cut filter and the glass cracked slightly on the extremity, very close of the ring itself. I don't think it's visible in the image, especially since the ursa mini is not full frame so there's always a crop factor. But i don't know if there's any property of light that might affect the whole image because of that scratch. Just wanted to know if it's a case of buying a new filter or keep using this one.

    I know scratches affect the sharpness, but since it's located next to the extremity, maybe it won't even show...
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  2. #2  
    Senior Member DPStewart's Avatar
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    You're right that a scratch way out on the edge 'probably' won't show.
    Bit if the filter is actually cracked then light could reflect off of the cracked glass into your image field.
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  3. #3  
    Senior Member david evans's Avatar
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    The glass is cracked on one side but it's fine on the other. I have an important shoot coming this thursday and it can't be compromised. Is there any important test I can do besides just filming something? What kind of artifacts should I be looking for in the image?

    Thanks
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  4. #4  
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    Test it. Then you'll know.
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  5. #5  
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    Any crack or scratch is going to flare especially with light sources in the shot or specular highlights and reflections. If it's only on the edge cover both sides of the crack with paper tape and rotate the crack so that its at the top or bottom of the lens. For a 16:9 sensor you can only use the center half of a circular filter vertically and realistically you're using much less unless you're on an ultra wide lens.
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