10 Feb
2011
10 Feb
'11
1:53 a.m.
On Wed, 9 Feb 2011, Brent Hilpert wrote:
No, you've got that wrong. The bits only affect the starting and end point
of a vector but *not* the vector itself!
I don't know why you would say it's not correct. The numbers are out of the
book and refer to the abilities of the then-current RMA TV Committee
standards for transmission, they account for things like channel bandwidth.
Sure, and the newspaper is always right ;-)
Since TV is/was purely analog, the horizontal resolution only depend on
the bandwith and the beam focus.
It is a slightly different meaning than 'pixel' today, it's a measure of
resolution: that which can be resolved; rather than a fixed grid of points on
the image medium.
It's not an assertion by me, I'm just pointing out how these things were
characterised in 1940: even for analog systems they did so in terms of a
matrix or discrete count of "picture elements". There is a whole chapter in
No, they didn't. Maybe in the US, but usually they refered to the number
of scan lines ("vertical resolution" if you like) and the bandwidth
(e.g. 5.5 MHz here or around 10 MHz in France).
That's
exactly the point: those Tektronix terminals/computers are not
raster-scan systems, you draw a line from here to there. The only
"limitation" is the addressing range for the start and end point (either 10
or 12 bits). Speaking of the printer, AFAIK it's the printer that
determines the scanning speed and the resolution of the rasterization
process.
(And ultimately that 10 or 12 bits does place a maximum on the V*H resolution
of the drawn image.) systems at the time. The phrase "picture
element" is used throughout. The
then-current transmission standard was characterised as 441 lines by
400-600 picture elements per line, "that 3,000,000 to 6,000,000 elements
must be sent
... which is not quite correct since the horizontal "resolution" depends on
the bandwidth, the beam spot size and the size of the screen surface. in a second", etc. The characteristics of other
mediums such as
photographs are also presented in terms of picture elements.
?!? I know that the grain size matters, but where can I find those picture
elements on a film strip? the book on image analysis and it is more complex than
what I present here,
it doesn't correspond 1:1 in the V dimension to the number of scan lines for
example.
Well, the vertical dimension depends of the size of the CRT, the number of
scan lines remains the same (625 lines according to the CCIR). Some of
these lines are "drawn" outside the visible area of the CRT as they
contain the vertical sync and the blanking period (the B and S in (C)VBS).
"A single frame of 35mm motion picture film
contains about 500,000 picture
elements when exposed, developed and projected in the usual manner."
"A fine 'contact' photographic print of 8*10in dimensions contains as many
as
50,000,000 picture elements."
Sounds like marketing figures...
Christian