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Re: Eclair Cameras: 144 degree shutter
Thanks for the excellent analysis below. I wonder if it's possible to have a variable shutter on the ACL.
----- Original Message -----
Sent: Friday, July 11, 2003 1:43 AM
Subject: Eclair Cameras: 144 degree shutter
The original design of the Regular-16 ACL allows for just enough time for the mirror to pass in front of the R-16 aperture opening while the 175 degree shutter is closed.
When the aperture is enlarged to S-16, a part of the mirror will still be in front of the track-side of the aperture when the 175 degree shutters opens up again. Compounded by the fact that the mirror is now off-center, technically, every second frame has a theoretical underexposure along the far track-side edge of the image.
Most folks who have used the ACL with the aperture widened to S-16, but with the shutter left alone, have reported that the resultant image is fine to their eye. It may be that the degree of underexposure on the track-side edge is so tiny as to not be a factor, or it may be that in projection or transfer to TV the very edge is cut off anyway.
None-the-less, the HD-144 Shutter, (and indeed the entire HD-144 Super-16 conversion kit), was created to fill a vacuum for those ACL users who want their camera to be at 100% theoretical Super-16 specs. Neither an Arri nor an Aaton has even a fractional exposure difference from side to side, and I wanted my personal ACL to be up to the hypothetical 100% factory specs that Eclair would have specified if they had put out a factory S-16 ACL (in fact they had a prototype, see the ECLAIR PANARAM promo sheet at www.members.aol.com/super16acl .)
My general feeling is that if one is using an older ACL 1 with the small motor, and not worth all that much, just go with the cheapest possible conversion that seems to work for you.
But if you are modifying an ACL II package in great condition and worth $5,000, why not do everything up to perfect specs for peace of mind --- especially if using the camera professionally or for that personal film that you are sinking $25,000 into. For myself, there was also this 'pride of ownership' thing --- I wanted my ACL to be theoretically up to the same S-16 specs as an Arri or Aaton.
If an ACL intended for use in Europe retains the original shutter (for use with 50 cycle HMIs), then re-centering the mirror is even more important to at least keep from making the theoretical edge underexposure more than it needs to be.
The other advantage to the 144 degree shutter is that when shooting an NTSC TV screen, instead of a big ugly roll bar you get two very narrow lines. And by running at 23.96 the lines can be frozen.
144 degrees also makes the camera's shutter speed 1/60th/sec (a 1/3rd light loss), which is a photographically significant speed for eliminating flicker with some 60 cycle power situations, like older HMIs or street lights.
Theoretically as well, at the faster 1/60th of a second exposure a moving image will be marginally sharper than when exposed at 1/49th of a second. I know TV DPs shooting 16mm who will use the 144 degree shutter on their Arris and Aatons for that reason alone.
But opinions vary, as we have seen before on this site. Check the archives. Mark.
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