[tig] viewing distances

john.pytlak at kodak.com john.pytlak
Tue Sep 28 18:57:35 BST 2004


Again, the specifications in standard SMPTE 196M-2003 "Indoor Theater and 
Review Room Projection --- Screen Luminance and Viewing Conditions" would 
certainly seem to apply to any images ultimately viewed on a theatre 
screen, even if viewing a DI electronically projected.

SMPTE Standards are available here:

http://www.smpte.org/smpte_store/standards/

The pertinent part of SMPTE 196M regarding viewing distance and angle is:
______________________________________________________________________________________
9 Review room viewing conditions
All observers in a review room shall be located within a standard 
observing area which shall be:
a) within the limits of a 15? angle on either side of a perpendicular to 
the center of the screen, in both the
horizontal and vertical planes; and
b) at a distance of 3 picture heights ? 1 picture height from the screen.
_______________________________________________________________________________________

Television standard SMPTE 148-2002 also may apply:

______________________________________________________________________________________
A.1 Viewing conditions
During preparation of motion pictures , the producer, the motion-picture 
film laboratory personnel, and others examine
the film many times from the original test shots through many stages to 
the final release prints. The films are projected in a
specialized theater known as a review room. These installations are 
designed to permit judgments of projected picture quality
and determinations of the suitability and acceptability of release prints, 
daily and work prints, production tests, printer and
processing tests, etc. The rooms are constructed to accommodate a small 
reviewing group of usually 10 to 20 people. The
actual picture size may be large or small, depending upon the space 
available, but the viewing conditions are chosen to
duplicate as nearly as possible actual conditions whether the print is 
intended for theatrical viewing or television transmission.
All viewing conditions are capable of being precisely controlled and 
should be held to a minimum tolerance.
______________________________________________________________________________________

SMPTE Recommended Practice RP166-1995 applies to viewing conditions for SD 
video on a monitor:

_____________________________________________________________________________________

3.3 The observer's distance from the monitor
screen should be 4--6 picture heights.
3.4 The observer should view the monitor
screen at a preferred angle in both the horizontal
and vertical planes of 0? ? 5?, but no greater than
? 15?, from the perpendicular to the midpoint of
the screen .
_________________________________________________________________________________________

The SMPTE Standards are there to guide you, and if new standards or 
revisions are needed, there is a process to do it.

John
(signed by:)
John P. Pytlak
Senior Technical Specialist
Customer Technical Services
Entertainment Imaging
Research Labs, Building 69, Room 7525A
Eastman Kodak Company
Rochester, New York 14650-1922  USA
Telephone: +1 585 477 5325
Cell: +1 585 781 4036
Fax: +1 585 722 7243
e-mail: john.pytlak at kodak.com
website: http://www.kodak.com/go/motion



It is interesting too because in audio dubbing suites there is a similar
problem. I recall one ex-colleague (Billy Mahoney, Head of Audio at
Molinare) pointing out the need for mixing to a large projected image, 
even
for TV drama, so that they didn't miss some minor action on screen that
needed a bit of foley that might well have been missed on a 20" monitor.
Given that the colourist is creating complex masks amongst other detailed
adjustments, I can see the need to be absolutely certain that they still
work on a full size cinematic screen.

Another person I was talking to recently reported that a DoP had said that
they liked a screen size that enabled them to see the entire screen, as
large as possible but without having to move their heads around to take it
all in.

Unlike TV, which is where most of us have come from, nothing is really 
fixed
in the new world. Aspect ratio, type of display (Might be cinema via 
digital
projector or via a print, might be a TV screen or even, shudder, a phone),
viewing conditions, delivery method etc

Anyway thanks to everyone for the links and thoughts.

Hugh
-----------------------------
Hugh James Waters
Waters Technical Services
07801 053248
01453549048
hugh at hjwaters.co.uk
www.hjwaters.co.uk


>
> Cast in stone from SMPTE was 3.5 x diagonal ...  cant remember the
> angle, something like 10/15 degrees ..... Although it was a written spec
> it was never practical to use ...
>
> Graham Collett
> Sprockets(telecine) Ltd
> www.sprockets-telecine.co.uk

> >
> > What, for example, is the optimum viewing distance from the screen and
>
> > are there any rules of thumb (or actual specs) to suggest any
> > particular physical size of screen to use?
>
> Without answering the question or citing hard data, I can report on
> "conventional wisdom" regarding a way the "cinema experience" differs
> from the "big screen TV" experience.
>
> Our perception of a moving image depends not only on the angular size of
> the visual field, but also the absolute distance. A 4-foot screen viewed
> from 10 feet is not the same as an 8-foot screen from 20 feet. Above a
> certain distance (roughly 20 feet), our stereoscopic vision becomes
> pretty weak. Binocular disparity then tells us only that things are
> "far", not that they are all on a flat surface at the same distancen
> away. Thus, other 3-D cues (obscuration, relative motion, haze, etc.)
> dominate and are not being contradicted by stereopsis. The cinema "big
> screen" therefore gives a better impression of dimensionality than a
> smaller, closer screen with the same viewing angle, resolution, color,
> etc.
>
> I'm just reporting the effect. I'm not saying that a DI suite should
> have a screen 20+ feet from the operator in order to do "accurate"
> grading!
>
> Cheers,
>   Chuck












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