Ground Glass vs Reality
More often than not in cinemas I can see projected image on the black
borders of the screen. My question is how accurate are the camera GG markings
to what is seen on the cinema screen.
Television GG standard have a TV safe marked where you know picture information
enters the twilight zone and may or may not be seen at home.
Should GG marked up for a theatrical release do the same ? I suspect most
cinema projection set ups cut off more picture than a good modern TV set
Is there a standard for cinemas and is that reflected in camera GG's ?
Tom Gleeson wrote:
>More often than not in cinemas
I can see projected image on the black >borders of the screen.
Note that most theatre aperture plates are hand-filed to deal with things
like keystoning. There's also going to likely be some mismatch between
screen size/lens focal length/throw.
Tom Gleeson wrote:
>"More often than not in
cinemas I can see projected image on the black >borders of
This is not a camera problem, but problems related to poor projection,
(1) The projector lens is "off centre" (the
eccentric adjustments are off, usually due to slamming the turret shut...
(2) Aperture plate in the projector is out of adjustment...
(3) or the black border (called masking) around the screen
is not in its correct position. The accepted procedure is to allow only
a hand's width of image shining on the masking. More than that requires
the engineer to fix the problem.
>"My question is how accurate
are the camera GG markings to what is >seen on the cinema
In the theatres which have been built in the last 10 years, quite good.
Older theatres can have severely cropped images due to not sizing the
lens to the auditorium. Contact me off list if you wish more information.
Projection set-ups I work with have no more than ten thousands of an inch
maximum crop side-to-side and top-to-bottom.
>"I suspect most cinema
projection set ups cut off more picture than a >good modern
TV set does.
The SMPTE recommended practices suggest that the projector aperture be
no wider than .825 of an inch horizontally--for both 'scope and flat (anamorphic
or 1:1.85) Allowing no more than a .010 inch crop all the way around the
aperture is considered good practice.
Jeff Kreines wrote:
>"Note that most theatre
aperture plates are hand-filed to deal with things >like keystoning.
There's also going to likely be some mismatch >between screen
size/lens focal length/throw."
Very true, and also to compensate for screen curvature, especially in
modern auditoriums which are wider than the projection throw. The focal
length of the projector lens is quite short, thereby requiring some fancy
>"How about burning a hard
matte (can be done easily in the IP stage) >onto the first
100 feet of each reel? Or the whole film? Of course it
won't >happen, as there's no money to be made with proper
Would you believe one distributor (studio) does it for all their films?
A few year back they were so apologetic because they cut one shot into
the finished IP which did not have the printed-in hard matte. Also, most
1:1.85 trailers have the matte since more than 90 percent of trailers
are done on the computer from scanned negative or print material. With
anamorphic prints, the lack of a matte is no problem since all of the
image is intended to be projected, but it really is needed on 1:1.85 prints.
Projectionist really don't have a sense of correct composition!
Wade I. Ramsey (the other Wade Ramsey)
Dailies Projectionist / Projection Engineer
Formerly Camera Assistant
Formerly Film Editor
Fort Mill, SC