[opendtv] Re: Line Pairs/millimeter vs. Price vs. Image Format Area
- From: Mark Schubin <tvmark@xxxxxxxxxxxxx>
- To: opendtv@xxxxxxxxxxxxx
- Date: Sun, 03 Jun 2007 22:20:30 -0400
Manfredi, Albert E wrote:
I'm not a broadcaster. My guess is that the TV industry years ago
evolved a set of 2/3", 1/2", and 1/3" standards for electronic image
acquisition that were convenient, and lower cost, than the movie
industry's standards.
The first commercial U.S. camera tube, the iconoscope, had a
photosensitive area the size of an index card. That was followed by
image orthicons (the smaller of which had the larger image area) and
later by vidicons, of which the lead-monoxide Plumbicon was a subset.
The first Plumbicons were inch-and-a-quarter format, followed by one
inch. It wasn't until the Ikegami HL-33, the first real color
shoulder-mount camera, that 2/3-inch tubes became popular. Until VERY
recently, there was virtually nothing smaller than 2/3-inch format
(Philips briefly flirted with half-inch).
And my guess is that this happened because the
image quality of analog TV could afford to be *very* inferior to that of
the movie industry.
That was never an issue. The issue was simply making cameras small
enough to be portable in the age of tube-based imagers. Because color
video cameras use prism-based color separation, they could never
directly use movie or still camera lenses because the latter didn't have
the necessary back focal length.
So, while TV shows were shot and archived in 35mm or
16mm film, live studio or on-location video was acquired to a much lower
image quality standard. Hence, tiny lenses and tiny imagers.
Actually, very large lenses and tiny imagers. The lenses had to be
large in diameter to accommodate the limited sensitivity of the imagers
and long to accommodate the many individual pieces of glass necessary
for constant-focus zooming and aberration correction.
Furthermore, my guess is that when DTV came about, there was a real
incentive for the TV production chain to stick with these PAL/NTSC image
acquisition hardware standards (cameras, lenses, lens mounts), and this
was still feasible with SDTV.
It's interesting. The first chip-based HDTV cameras used the 1-inch
imaging format, but they shifted to 2/3-inch to allow the use of
existing lenses.
Furthemore, my guess is that for HDTV, the TV industry naturally wanted
to continue to use their 1/3", 1/2", and 2/3" equipment, but that this
required the sort of heroic lens improvements that the BE articles Craig
posted talk about.
See above. There were no 1/3-inch systems and almost no 1/2-inch.
So that's why everyone seems to operate on the
assumption that HDTV lenses must be amazingly expensive.
They're actually a tiny fraction of the cost of the HD lenses I used in
1989 and 1990.
These lenses
are only used for TV, they are very small comparatively,
Again, the lenses are quite large. The HDTV lens I most commonly use at
the Metropolitan Opera, Fujinon's XA101x8.9, is 252 x 252 x 666 mm and
weighs 22.9 kg. It's for a 2/3-inch format.
and they must
be made to very high optical standards to compensate for their
diminutive size.
Wrong about the small size, right about the critical standards.
I think Mark Schubin listed many larger HDTV camera standards that aim
to get beyond the restraints caused by the tiny lens formats. I added
the diagonal dimensions that correspond to the 1/3", 1/2", and 2/3"
sizes that the BE articles talk about, to show where they fall in the
long list. (Possibly these are not meant to represent exact diagonal
dimensions.) Also, I added medium format and 35mm frame formats on top
of the list, to show that they fall right up there with the biggest
options listed, and could make use of very competitively priced lenses
to easily achieve 2 Mpel image quality, and posssibly much more, with
the better 35mm lenses.
Actually, your video additions are incorrect. Video format sizes refer
to the outside diameter of the tubes (back when there were tubes). The
photosensitive areas were smaller. Thus, a one-inch format has a
photosensitive area diagonal of 16 mm, not 25.4. A 2/3-inch format is
11 mm, 1/2-inch is 8 mm, 1/3-inch is 6-mm, and 1/4-inch is 4.5 mm.
Something similar is true in film, which is why 35-mm refers to the film
width, whereas the image width is considerably smaller.
TTFN,
Mark
75.0 mm diagonal (4.5 X 6 cm medium format)
43.3 mm diagonal (still 35mm or VistaVision formats)
30.0 mm diagonal (35mm movie and approx APS formats)
-------Mark Schubin's list--------
59.6-mm diagonal 4096x2440
38.1-mm diagonal 4000x2048
35.6-mm diagonal 1280x1024
30.8-mm diagonal 3018x2200
29.1-mm diagonal 2048x2048
28-mm diagonal 4520x2540
27.5-mm diagonal 5760x2160 (16:9 aspect ratio)
24.6-mm diagonal 1024x1024
20-mm diagonal 1536x1024
19-mm diagonal 1280x1024
*** 16.9 mm diagonal = 2/3" ***
16-mm diagonal 1920x1080
16-mm diagonal 1280x720
*** 12.7 mm diagonal = 1/2" ***
11-mm diagonal 1920x1080 with 2nd green with half-pixel diagonal offset
11-mm diagonal 1920x1080 - most common high-end professional
11-mm diagonal 1280x720
11-mm diagonal 960x540 with half-pixel diagonal offset between green and
red/blue (16:9)
*** 8.5 mm diagonal = 1/3" ***
8-mm diagonal 1440x1080 (16:9)
7.1-mm diagonal 1280x720 effective (from higher-resolution filtered)
6-mm diagonal 1920x1080
6-mm diagonal 1440x1080 with half-pixel horizontal offset (16:9)
6-mm diagonal 960x1080 with horizontal offset (16:9)
6-mm diagonal 960x1080 with diagonal offset (16:9)
4.5-mm diagonal with pixel-grid rotated 45 degrees, (960x540)x2 (16:9)
4.5-mm diagonal 960x540 with diagonal offset
-------------------------------
Bert
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