Subjective
tests have indicated that best viewing comfort, panoramic effect and artistic
appreciation are obtained when the picture raster has a rectangular format with
an aspect ratio, i.e, width to height ratio of 4:3. This is because of the
binocular vision due to the pair of eyes in the horizontal plane as compared to
that in the vertical plane.
tests have indicated that best viewing comfort, panoramic effect and artistic
appreciation are obtained when the picture raster has a rectangular format with
an aspect ratio, i.e, width to height ratio of 4:3. This is because of the
binocular vision due to the pair of eyes in the horizontal plane as compared to
that in the vertical plane.
Also
the fovea, the region of maximum resolution at the centre of the retina has
greater area along the width them along the height. A larger width of the
raster ensures a more efficient use of the area of the fovea. In motion picture
industry, the aspect ratio of 4:3 had been accepted until the advent of
Cinerama and stereophony technique. In television system also, the picture
format with an aspect ratio of 4:3 is commonly employed as it is most pleasing
aesthetically and less fatiguing to the eye.
the fovea, the region of maximum resolution at the centre of the retina has
greater area along the width them along the height. A larger width of the
raster ensures a more efficient use of the area of the fovea. In motion picture
industry, the aspect ratio of 4:3 had been accepted until the advent of
Cinerama and stereophony technique. In television system also, the picture
format with an aspect ratio of 4:3 is commonly employed as it is most pleasing
aesthetically and less fatiguing to the eye.
For
High Definition Televisions intended to give better quality wide screen
pictures, a larger aspect ratio has been favoured. The Japanese Broadcasting
Corporation NHK who pioneered work in HDTV, conducted psychological experiment
on the size of the screen, the aspect ratio, the angle of vision, for giving
the sense of impact and reality. A wider field of vision was required to evoke
the visual psychological effects of high level viewing, especially during large
screen projection. They found a larger aspect ratio desirable and selected 5:3.
High Definition Televisions intended to give better quality wide screen
pictures, a larger aspect ratio has been favoured. The Japanese Broadcasting
Corporation NHK who pioneered work in HDTV, conducted psychological experiment
on the size of the screen, the aspect ratio, the angle of vision, for giving
the sense of impact and reality. A wider field of vision was required to evoke
the visual psychological effects of high level viewing, especially during large
screen projection. They found a larger aspect ratio desirable and selected 5:3.
An
aspect ratio of 16:9 is favoured to give greater flexibility in shooting and
releasing TV programs. By using a shoot and protect scheme with an aspect ratio
of 16:9, releases could be made in any aspect ratio between 4:3 and 2.35:1 as
shown in figure 1 below.
aspect ratio of 16:9 is favoured to give greater flexibility in shooting and
releasing TV programs. By using a shoot and protect scheme with an aspect ratio
of 16:9, releases could be made in any aspect ratio between 4:3 and 2.35:1 as
shown in figure 1 below.
If
the master shooting has a 16:9 aspect ratio, a 4:3 aspect ratio release uses
the full height of the master and appropriate width. A release with 2.31:1
aspect ratio can use full width of the master and appropriate height. Other
releases can use either full height or full width. Critical portions are
contained in the inner rectangle while the extended rectangle forms the 16:9
aspect ratio master as seen in figure 1 above.
the master shooting has a 16:9 aspect ratio, a 4:3 aspect ratio release uses
the full height of the master and appropriate width. A release with 2.31:1
aspect ratio can use full width of the master and appropriate height. Other
releases can use either full height or full width. Critical portions are
contained in the inner rectangle while the extended rectangle forms the 16:9
aspect ratio master as seen in figure 1 above.
For
picture raster of rectangular shape, rectilinear scanning is most convenient.
There are two scanning procedures taking place simultaneously, one moving the
beam horizontally from left to right at a fast rate and the other moving the
beam vertically downwards at a slower rate. Movement of the beam are at
constant speeds during the forward and the downward scans and the scanning is
thus linear in both directions. Figure 2 below illustrates the beam paths and
deflection fields for producing the picture on the picture tube screen.
picture raster of rectangular shape, rectilinear scanning is most convenient.
There are two scanning procedures taking place simultaneously, one moving the
beam horizontally from left to right at a fast rate and the other moving the
beam vertically downwards at a slower rate. Movement of the beam are at
constant speeds during the forward and the downward scans and the scanning is
thus linear in both directions. Figure 2 below illustrates the beam paths and
deflection fields for producing the picture on the picture tube screen.
The
beam travels in both horizontal and vertical directions as shown by the
continuous lines. The broken lines indicate the retrace which occurs rapidly
with respect to the forward scan and is normally blanked by cutting off the
beam in the picture tube as well as the camera tube, both during the horizontal
and vertical retrace.
beam travels in both horizontal and vertical directions as shown by the
continuous lines. The broken lines indicate the retrace which occurs rapidly
with respect to the forward scan and is normally blanked by cutting off the
beam in the picture tube as well as the camera tube, both during the horizontal
and vertical retrace.
For
each vertical scan, the picture is assumed stationary, and is scanned at a fast
rate along a number of horizontal slanting lines. For good resolution, the
number of lines scanned per picture must be large enough. The scanning lines
must not be disturbingly visible to an average viewer at a distance of about
five to six times the picture height. A relatively low vertical scanning rate
is desirable because it allows the beam to scan large number of horizontal
lines with reaching an inordinately high horizontal scanning frequency. The
lower limit to the vertical scanning rate is set by the limit of persistence of
vision of the human eye.
each vertical scan, the picture is assumed stationary, and is scanned at a fast
rate along a number of horizontal slanting lines. For good resolution, the
number of lines scanned per picture must be large enough. The scanning lines
must not be disturbingly visible to an average viewer at a distance of about
five to six times the picture height. A relatively low vertical scanning rate
is desirable because it allows the beam to scan large number of horizontal
lines with reaching an inordinately high horizontal scanning frequency. The
lower limit to the vertical scanning rate is set by the limit of persistence of
vision of the human eye.
