Thread: Spots on images - Does anyone know what this is?

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  1. #1 Spots on images - Does anyone know what this is? 
    Senior Member Josef Gatti's Avatar
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    Hi Guys,

    Just a quick one, I've got a few black spots on my pictures, just wondering if anyone can recognize them. They're consistently in the same place, and do not change depending on focus, so it's not the lens. I've blown air onto the OLPF and given it a quick wipe, the spots still stay in the same place. Can anyone recognize if this is dust on the actual sensor? Or is it damage to the sensor? Or could this simply be stuff on the OLPF? Note that this is a 100% crop.

    Note that the do change in visibility depending on exposure. A really bright light source (say pointed at the sky) will wash them out.

    I will be sending the camera to RED in the next few weeks, though I'm a little anxious, and would love the peace of mind knowing what it is, if anyone might know.

    Cheers

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  2. #2  
    Moderator Phil Holland's Avatar
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    Very weird. Are they always this size and shape? I initially thought dust on the OLPF or even Coverglass, but they have a size to them. Any lasers near this sensor?
    Phil Holland - Cinematographer - Los Angeles
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  3. #3  
    Senior Member Josef Gatti's Avatar
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    Identical every time Phil, always the same shape and position. No lasers that I know of. It's been on a couple of rentals before but I've never noticed them until recently since we were doing some green screen stuff, and I often shoot at 4k (only visible at 5k).

    Here is the full image:

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  4. #4  
    Moderator Phil Holland's Avatar
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    Hmmm. Really weird. Make a log and send it to your Bomb Squad Rep for sure. It could be a few things. If they are the same size like that in the same position it's likely sensor related. I've seen weird laser damage before and it's resulted in similar dots, marks, and patterns. Though it's hard to tell what's up here. Maybe strobing lasers from a concert or something would create that. Could be a few other things though.
    Phil Holland - Cinematographer - Los Angeles
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  5. #5  
    Senior Member Josef Gatti's Avatar
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    Thanks Phil, appreciate it. Have already started some dialogue with RED and will be sending it soon. Just stressed out of my mind is all. If anyone else knows if this could simply be the OLPF, would be good to hear your experience. I too think that the consistency with the blemishes on the image must make it sensor related, but who knows. OLPF scratches perhaps?
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  6. #6  
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    Quote Originally Posted by Josef Gatti View Post
    Thanks Phil, appreciate it. Have already started some dialogue with RED and will be sending it soon. Just stressed out of my mind is all. If anyone else knows if this could simply be the OLPF, would be good to hear your experience. I too think that the consistency with the blemishes on the image must make it sensor related, but who knows. OLPF scratches perhaps?
    Not so much scratches but debris.

    Do they blur when you iris?

    Have you examined the OLPF with a loupe, front and back? With folks removing those now you may need to check both sides as well as the cover glass. Is this a Dragon?
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  7. #7  
    Moderator Phil Holland's Avatar
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    If the blemishes, dust, or whatever are on the OLPF I imagine you'd be able to see it with a flashlight. Though one of the reasons RED's OLPF is further away from the sensor is to help with nasty things like that not being as visible.
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  8. #8  
    Senior Member John Marchant's Avatar
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    I'd be pretty much 100% sure that's dust on the sensor cover glass. It's seldom so sharply focussed as that when there's dust either side of the olpf
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  9. #9  
    Senior Member Josef Gatti's Avatar
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    This is actually MX. I've been wanting to remove the OLPF to look at it more closely, but there are little RED stickers on it which I'm guessing are for warranty. Do you know if it would be a problem (considering my camera isn't under warranty anyway) if I remove the OLPF and break the stickers?

    The blemishes do not change with focus, nor do they blur with iris, but they aren't as obvious when wide open, but clearly still there.
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  10. #10  
    Senior Member Josef Gatti's Avatar
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    Development:

    It's definitely not the OLPF - I stripped the lens mount off the camera, set the shutter to around 1/500 and put my iphone light in front of the OLPF and wiggled it around. It resulted in highlighting some dust and whatnot on the olpf, though it the dust/scratches shadows would wiggle around as I would wiggle my light source around. The blemishes on the image stayed in their exact same position and shape, while all the crap on the OLPF danced around.

    Looks like it is the sensor, I guess now it's just a case of whether or not it is damage or just some stuff that can be cleaned off there.
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