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Lens Flare? Light Leak? Processing error? What is it?


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#1 jake carl magee

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Posted 01 July 2009 - 07:11 PM

I shot some test rolls for a recent project and the first roll had a strange washout through the whole roll. Anyone have any idea what it might be? Look at the weird ghosting that happens at 1:48. nHowever, notice that the second roll (graveyard) didn't have the issue.... any ideas? Also, do you think the jittering frame issues might be resolved with smoothcam in final cut? thanks!


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#2 Chris Keth

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Posted 01 July 2009 - 07:36 PM

My feeling is that you probably have a small light leak when that spot of the camera is hit by direct sun. In the cemetery, perhaps that place on the camera was shaded
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#3 Jim Keller

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Posted 01 July 2009 - 08:11 PM

Your second roll seems to also have the issue. I noticed the same ghosting at 4:31. It's just doing a better job of hiding in a more complex scene with fewer broad swaths of subtle gradiation.

To me it looks like a lens aberration. I'd suggest trying another test roll with a different lens on the camera.
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#4 Chris Millar

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Posted 01 July 2009 - 10:23 PM

First thing I think of with Bolexes and light leaks is a missing filter holder...

As for the ghosting, thats pretty neat - maybe a focused light source is being refracted/reflected a little somewhere. Inspect the neg to determine if it is a transfer issue first, then the inside of the camera lens mount, prism and gate. Having thought about it a little, prism could be the go actually (assuming its RX).
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#5 jake carl magee

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Posted 02 July 2009 - 12:37 AM

I shot some test rolls for a recent project and the first roll had a strange washout through the whole roll. Anyone have any idea what it might be? Look at the weird ghosting that happens at 1:48. nHowever, notice that the second roll (graveyard) didn't have the issue.... any ideas? Also, do you think the jittering frame issues might be resolved with smoothcam in final cut? thanks!


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Upon some further examination- it looks like the aperture on my lens (kern switar poe bayonet) when all the way closed down, has a leak around the outside the edge of the iris. It looks like a large "c" inside of the lens. Is it possible that this is what the problem is? In the dunes I was all the way closed down, but in the graveyard I was at f8 or so, reducing the gap around the iris diaphragm... either way, looks like I need some major repairs... not to mention the registration jiggle.

thanks!
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#6 Chris Millar

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Posted 02 July 2009 - 12:57 AM

Upon some further examination- it looks like the aperture on my lens (kern switar poe bayonet) when all the way closed down, has a leak around the outside the edge of the iris. It looks like a large "c" inside of the lens. Is it possible that this is what the problem is? In the dunes I was all the way closed down, but in the graveyard I was at f8 or so, reducing the gap around the iris diaphragm... either way, looks like I need some major repairs... not to mention the registration jiggle.

thanks!


The iris in a POE is actually two blades each with kinks in them that form roughly a square when closed down - if they weren't adjusted properly and closed too far light may fall around the outer edges of them as you describe ...

The area of the lens however at these points should still be a part of the image forming 'solution' and simply over expose your images (which may well make up for the under exposure from the initial misalignment :lol: ) - anyhoo, there is also another mirror/prism thingy in there which directs light up to the meter on the POE, maybe you are letting some stray light into areas of this that aren't so awesome when it comes to forming a coherent image.

This would also explain why your other footage may well be fine, in that the blades were at f8 and wouldn't allow this extra squeak of light through the lens.

Try this:

Open your lens fully up (iris that is) then close it slowly noting when the iris blades actually start to appear - if on the little scale dingalingy thingy you are stopping down already and the blades have failed to appear then at least you have an issue with correct iris referencing and I might be right about the rest. You'll also likely spot the prism I refer to, see if it is in the area that the blades form that C shape.

I have opened these up to fix previously - both the POE and PTL - in Australia at the moment though
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#7 Jean-Louis Seguin

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Posted 02 July 2009 - 07:43 AM

Upon some further examination- it looks like the aperture on my lens (kern switar poe bayonet) when all the way closed down, has a leak around the outside the edge of the iris. It looks like a large "c" inside of the lens. Is it possible that this is what the problem is? In the dunes I was all the way closed down, but in the graveyard I was at f8 or so, reducing the gap around the iris diaphragm... either way, looks like I need some major repairs... not to mention the registration jiggle.

thanks!



I suspect one of your aperture blades has popped off it's guide post.
The aperture opening should look like a slightly elongated square at all settings.

With one blade out of position, exposures would be way off at certain settings.
It's usually not a major repair to correct this.

Cheers,
Jean-Louis

Edited by Jean-Louis Seguin, 02 July 2009 - 07:45 AM.

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