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Flickering lense flare


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#1 Travis Cline

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Posted 23 February 2006 - 05:07 PM

I've noticed a few times that I get a flickering lense flare. I've seen it when using tungsten lights, so I know its not a speed issue or any sort of HMI/flourescent problem. It occurs when the light giving me the flare is just out of frame and is hitting the lense at about a 35 degree angle. For instance, if I am panning into a scene the flicker only occurs when the light is in the 35 to 25 degree area and then when the light is in the shot it is no longer a problem. I don't see the flicker in camera, only in post. Could it be a defiiciency with the lenses? I've seen it on Zeiss Super speeds, Panavision Ultraspeeds, and Panavision Superspeeds. I have not seen it on Cooke S4's yet, but it also does not always occur with these other lenses. It only happens occasionally at best. Could it be a light fixture problem? Anyone seen this, know what I am talking about?

Travis
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#2 Trevor Greenfield

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Posted 23 February 2006 - 05:17 PM

I had it happen on High Fire Danger! during an EXT sunny day shot looking in the direction of the sun with the angle from the source being 40 degrees or so. And that was with the stock Meteor lens on the K3 and most likely at least 1.2 ND I'll have to go back and look. Looks like a fluttering insect or something.
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#3 Leo Anthony Vale

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Posted 23 February 2006 - 05:47 PM

I've noticed a few times that I get a flickering lense flare. I've seen it when using tungsten lights, so I know its not a speed issue or any sort of HMI/flourescent problem. It occurs when the light giving me the flare is just out of frame and is hitting the lense at about a 35 degree angle. For instance, if I am panning into a scene the flicker only occurs when the light is in the 35 to 25 degree area and then when the light is in the shot it is no longer a problem. I don't see the flicker in camera, only in post. Could it be a defiiciency with the lenses? I've seen it on Zeiss Super speeds, Panavision Ultraspeeds, and Panavision Superspeeds. I have not seen it on Cooke S4's yet, but it also does not always occur with these other lenses. It only happens occasionally at best. Could it be a light fixture problem? Anyone seen this, know what I am talking about?

Travis


---If it's happening when panning, it's a shutter artifact.

Is the panning speed also a factor?

---LV

I've noticed a few times that I get a flickering lense flare. I've seen it when using tungsten lights, so I know its not a speed issue or any sort of HMI/flourescent problem. It occurs when the light giving me the flare is just out of frame and is hitting the lense at about a 35 degree angle. For instance, if I am panning into a scene the flicker only occurs when the light is in the 35 to 25 degree area and then when the light is in the shot it is no longer a problem. I don't see the flicker in camera, only in post. Could it be a defiiciency with the lenses? I've seen it on Zeiss Super speeds, Panavision Ultraspeeds, and Panavision Superspeeds. I have not seen it on Cooke S4's yet, but it also does not always occur with these other lenses. It only happens occasionally at best. Could it be a light fixture problem? Anyone seen this, know what I am talking about?

Travis


---If it's happening when panning, it's a shutter artifact.

Is the panning speed also a factor?

---LV

Edited by Leo A Vale, 23 February 2006 - 05:47 PM.

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#4 Patrick Neary

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Posted 23 February 2006 - 05:52 PM

it sounds like light bouncing off of your spinning mirror shutter.
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#5 DEMUTIGER

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Posted 23 February 2006 - 06:03 PM

What type of camera was it, or have you noticed this with more than one make?

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#6 Dickson Sorensen

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Posted 23 February 2006 - 06:09 PM

Check that the area around the lens side of the gate is painted black. I once owned a camera that had lost most of its paint around the gate (perhaps from cleaning with an orangewood stick) and lights just outside the picture area would create a flare onto the film.
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#7 Travis Cline

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Posted 23 February 2006 - 06:35 PM

I've seen it on Moviecam, Arri III, and Gold II. Shutter artifact does sound like it could be, but if so is there anyway to avoid that? The cameras were in good condition and certainly the shutter was in good order, ie painted black. I also forgot to metion that it has occured with filter and without filters. I believe I've always seen it when shooting at a more open aperture as well, but I'm not 100 percent I've never seen it at lower f/stops though.

Travis
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#8 Phil Rhodes

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Posted 23 February 2006 - 08:29 PM

"Lens"

Not "Lense"

Phil "Facial Tic" Rhodes
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#9 Mitch Gross

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Posted 23 February 2006 - 08:53 PM

It's called gate flare. It happens even with gates painted matte black, although to a lesser degree. I see this all the time--notice it on TV and at the movies and have had it happen to me as well. A point source or bright light transmitted through the lens hits the edge of the physical gate and causes a little blast of light to project onto the film. It can happen along all four sides and apart from repainting your gate and making sure there is no oil or moisture accumulated on it there is nothing you can do about it. Panning through practicals and street lights at night are the most common causes.
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#10 David Mullen ASC

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Posted 23 February 2006 - 09:49 PM

I've had that happen when lighting is striking the left edge of the frame where the shutter is coming from.
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#11 Travis Cline

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Posted 23 February 2006 - 10:27 PM

Thanks everyone, I thought I was doing something wrong, or more accurately that something was wrong with the camera. I guess its something we have to live with then? Also, lense is the dictionary as:


lense

n : a transparent optical device used to converge or diverge transmitted light and to form images

Not to be too particular, I learned that from a DP I worked for when I first started with this work. Thanks again though for all your help.



So, if the rental house gives me a metallic silver gate and I want to avoid this problem will a black gate help any or is it the same either way?

Travis

Edited by travisclinedp, 23 February 2006 - 10:28 PM.

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#12 Mitch Gross

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Posted 23 February 2006 - 10:31 PM

A black gate is better but it can still happen.
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#13 Travis Cline

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Posted 23 February 2006 - 10:46 PM

Thanks Mitch, I'll make sure to get a black gate next shoot and see how that affects it.

Travis
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#14 Phil Rhodes

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Posted 24 February 2006 - 07:03 AM

Hi,

3D Studio Max has been able to simulate this effect since R4 :)

Phil
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#15 Patrick Neary

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Posted 24 February 2006 - 11:05 AM

A black gate is better but it can still happen.


why would the gate cause a flickering flare? My understanding is that it's usually a leading or trailing edge of the shutter that catches the light and causes the flickering effect...
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#16 Mitch Gross

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Posted 24 February 2006 - 01:11 PM

The light can bounce off the gate onto the shutter or the light can be bouncing around inside the camera and then off the shutter edge to create flicker. The gate flares I originally described don't flicker too much, but they can pulse depending on how they hit and the design of a given camera. For instance, non-flickering gate flares can be a big problem in Aatons but the flickering type almost never happens because it is so tight inside the camera. The Arri 16BL rarely has steady gate flares, but the flickering ones can be quite a problem, especially with practicals at the top of the frame.
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