CML - Cinematography Information & Discussion
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16mm GreenScreenI am going to use green screen in a section of an upcoming 16mm spot to isolate some waving pennants and then bring them into a shot. not having a lot of16mm experience I wonder if one camera is better suited than another, SR or Aaton. thanks in advance tom weston I don't think that the camera really makes the difference, what you are looking for is probably a nice stock like the 45 to reduce any risk of grain. Serge Desrosiers DP The answer here is again Film, or Video? I will not debate which camera is steadier, (actually I had an old A.C.L. that was as steady as any SR I've ever compared it to.) However remember this, as I understand it, in telecine, 16mm is registered on the side of the film, as is the Aaton. So if the film is not slit precisely the image should not weave in the telecine, as the exposed image will still be in register with the edge of the film. However since the image in an SR, is registered to a pin during exposure, theoretically if the film edge isn't perfect in relation to the perfs, there may be weave. I am not sure exactly how film is registered in 16mm opticals, however I would guess it is by registration pin. This may not be an issue, if you are only dropping one image on top of another, and not doing split screens, and lining up matte edges, and the such. Of course if the camera you use is not up to specs, then good registration is highly unlikely.
Steven Gladstone Since the 16mm perforations were never designed for full registration pins, at Aaton we preferred to follow the 'One Line' (side guide) 'One Point' (claw dead point at very low speed) classic geometric alignment system. The end result is that XTRs deliver a frame to frame registration which is better than 1/2000 of the frame dimensions both vertically and laterally. Who else? There is a fixed guide and a lateral pressure guide at the image level on all Aaton cameras (like on telecines), as opposed to film channel top-right and bottom-left posts found on some other cameras; thus NO loop stiffness dependant lateral weave at all. Furthermore this lateral pressure guide, combined with the 8 micron vault shape of the rear pressure plate, insures such a perfect depth positioning of the film (good for breathless images) that the aperture top and bottom horizontal rails are no longer necessary: that is why a Super16 Aaton XTR shows much less dust and hairs on the picture than any other camera. Jean-Pierre Thanks for such great input. This kind of info is really helpful to those of us who work almost exclusively in 35. Myself, I am a visual effects specialist, and registration is of the utmost importance, hence the exclusive use of 35mm. In often asked about the feasibility of shooting something on 16, and till know I've always thought it was a really bad idea, primarily from the registration point of view. It's really helpful to know that is not necessarily the case. Thanks for the explanation!!! Don Canfield I spoke with someone recently who had been approached by a large broadcasting company to modify their SR3s to solve the weave issue. He was able to make a prototype gate that (at great expense) did somewhat solve the problem, but then the funding for the project (and many other things) was cut. He said the weave was often on the diagonal, due to the opposing loops in the SR magazine. (He doesn't really want to make these gates, so I won't mention his name.) Interesting... I think the Aaton proves that simple and elegant is usually the best approach. Jeff ""speaking in hushed tones"" Kreines Surely Jeff it would have been less expensive for the broadcaster to go with the AATON XTRProd rather than re inventing the wheel with expensive mods and then they could have the great benefit of AatonCode, integrated video assist and a 12 volt low power operating system just to name a few features! But then as they say ' you can lead a horse to water but you can't make it drink!' John Bowring. Whilst I think weave/stability may be a problem for those who print, and lets face it, it shows up less when projected than when composited on tape. I also believe that stability of any film is becoming less and less of an issue as it's very easy to stabilise an image later. We're arguing pink, lime green or scotchlight balls for a motion tracked shot at the moment. Geoff Boyle Many telecines (especially unmodded Ranks) also add weave to an image... you might run a test film through the telecine (a simple grid will do) to check its steadiness. Jeff Kreines - DeMott/Kreines Films thanks to all for advice on this question. we shot this week with an SR2 and it turned out great. I shot with and without a net and found that we were able to cut a matt just fine with the net so we are going with that version (I prefer the look). one interesting (surprising to me) effect. we shot a row of banners against the sky then lifted a 12x12 green screen (from Fore Peak in Orlando, fla., a great source for terrific and reasonably priced green screens) behind them and shot them again. the idea was to make a matte of the pennants that we could raise into the shot upside down thus creating a menacing jaw (hey, it wasn't my idea). the pennants were opaque white but aged to the point of being grey. they were back lit. against the pale blue, partly cloudy sky they were about 85 i.r.e. during the transfer, however, when the green screen was lifted behind them their value shifted to about 70 i.r.e. nothing changed from our angle. not the stop. not the lite hitting them. when I shot it I assumed the difference I saw was do to the contrast difference between the sky and the green screen but, low and behold, it was actually there on the negative. we had to ""fix"" the discrepancy with the quadra (guess who was the ""savior"") because we wanted the upper and lower ""teeth"" to match. it turned out fine but I still don't understand the density shift. tom |
