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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 <A HREF="www.members.aol.com/super16acl)">www.members.aol.com/super16acl</A>
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
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
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.
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