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Serious Problem or New Filter Effect*?!

Published : 14th October 2003


Hello Everyone,

I just shot my first Super 16 short film, and something happened to the image that I can't quite figure out. Around the outer edge of the bottom, left side, and top of the frame, the image seems to smear or streak inwards towards the centre of the frame from time to time. The smear is not very long, and mostly will be hidden by the 1:85 masking, and to top it all off, the director loves it (extremely lucky break!) but it very much concerns me, as I can not account for it. The smearing only occurs in our exterior day lit scenes, and mostly happens to just the highlights on an object. For example, in one dolly shot, the bright glint off a shinny object will smear inwards as it enters the frame, then the smear quickly disappears as it moves towards the centre.

This didn't just happen to only the highlight, but some times in our most brightly sun-lit scenes, it happened to bright coloured flowers, and sometimes the blue of the sky actually smeared in (faintly, but it's there). One time, it happened to a light bulb as it entered the frame, but at that moment it looked like a horizontal tear drop shaped flare. Then the flare went away as the light bulb moved toward the middle of the frame.

Let me give the particulars :

It happened on our Kodak 7246 - 250D and our 7245 - 50D scenes, but not inside on our 7218. Outside, most times we were using a 4x5 Antique Suede and a round polarizer, but sometimes went with just the polarizer. Because of the Suede, the polarizer, and the over exposing 1 stop for the super 16 to 35 blow-up, our ASA on say the 50D was 5, and the 250D was considerably lower as well. We used mostly B-mount Zeiss super speed 16mm primes and had a PL-mount adapter that we put on each lens as it was used, but we also had a hard PL-mounted 9.5mm that didn't need our adapter.

The smearing occurred with all the lenses. We were also using an Eclair ACL II camera, that had a PL-mount adapter on it, so as to accept the PL-adapter mounted B-mount lenses, and the hard PL-mount 9.5.

(Whew! Ya still with me?) Ok with all that said, my best guess is that the problem is somewhere in the PL-mount adapter that is on the camera.

Could it be that light is leaking in somewhere and bouncing around some how and causing this aberration? Is the lens not sitting flush enough in front of the camera gate? Our footage markings on the lenses were way off with the focusing to our eye, but I attributed that to the adapter in adapter issue.

Sometimes with in the smearing, you can see the image that is outside of the frame being pulled in slightly. It's incredibly baffling.

Ok, I think I have explained all the parameters that led to this image issue. Any thoughts, guess, or ideas would be most appreciated, as I would like to avoid this problem in the future...unless the director wants it! Oh and one more thing, I just saw the latest Ridley Scott film "Matchstick Men", and there were a few moments in the film, were I saw the EXACT same aberration happen around the edge of the frame.

That made me feel a little better, like I'm not the only one in the universe that this has happened to.

Mike Gillis
Gaffer-Milwaukee, WI



Mike Gillis wrote of "a problem he had with light streaks..."

Mike,

I'm guessing that the problem is a light kick off the edge of the aperture plate. Common with older Aatons and ACL’s. You can thin the plate by filing carefully to reduce (and change the angle) of the edge so it doesn't divert light right at the edge of the frame into the image, and blacken it - or else live with it.

I once had this problem with an optical printer at DuArt, and no one there would admit to seeing the image, until I met David Leitner, who not only saw it, but made a special mask for their wet gate out of hi-con cut with an x-acto knife to make the spill from the oversized aperture on the projector side of the printer, as there was nothing that could be done in the Oxberry camera's aperture.

Jeff "hates that light kick" Kreines



>Around the outer edge of the bottom, left side, and top of the frame, the >image seems to smear or streak inwards towards the centre of the >frame from time to time.

As the S16 aperture cuts out the sound area, you might look for shiny edges in that area between lens seat and said aperture and make sure with matte black paint that all such parts are covered.

Check also the back and edges of the shutter.

Such streaks as you describe in your post happens only if the light enters the lens in a particular way that points to some kind of reflection, not a light leak.

BTW, were your camera's converted from normal 16 or original factory built?

Robert Rouveroy csc
The Hague, Holland

I plan to live forever. So far, so good.



I'm not sure if that's terribly bad or not, as you inferred...there are CGI programs which will simulate edge-of-frame gleams from bright light sources.

Due to this I always assumed it was a lens effect, but I guess you learn something every day.

Phil Rhodes
Video camera/edit
London



Mike,

Its always hard to analyse image/camera problems from a word description. If you could post an image you would get more definitive answers. But from your description of the "light streaks'' one possible cause may be a mistimed shutter. When this happens the shutter is not closed fully before the movement starts pulling the film down to the next frame. The light streaks show up most in the highlights as you describe.

Also it can be worse or better in different areas of the film depending on the geometry of the shutter to the gate and the extent of the mistiming.

Many Thanks
Tom Gleeson DP
www.cinematography.net



You are experiencing classic gate flare, aka Shiny Gate. This can be a problem on Aaton gates (mostly older ones) and ACL gates (all in the family...). I had to replace the shutter in my camera and have the gate edges milled down and repainted to eliminate this effect. Park your frame with a bright light along the frame edge and you could have a serious problem. I've seen this problem crop up on other cameras and in 35mm, but the larger format usually helps minimise the effect.

Did you say you could see the effect through the eyepiece? If you could then it's NOT a gate flare, but in fact something in your optics. If it was not visible in the eyepiece then it's likely occurring at the gate and possibly on the edge of the shutter, although the unique design of the ACL's swinging mirror shutter makes me doubt this.

That brings up another question : who converted your camera to Super -16?

I know that Les Boscher and Movie House in England offer different levels of conversion, with some accommodations being made to the shutter angle and timing to protect the larger gate.

If this was not done, then it could possibly create the problem you describe.

Mitch Gross
NYC DP