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#31
12-06-2006, 03:29 PM
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Quote:
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#33
12-06-2006, 10:34 PM
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Regarding interlace effects in tube-pickup cameras: the lenses were never designed to reduce this effect. doing so would reduce the over-all impression of sharpness too much. The scanning spot size in the pickup tube, however, was made large enough that it would scan the whole target in one field, that is, the spot was wide enough to discharge the spaces between the lines as well as the lines themselves. If it happened that the spot was too sharp, you would get a fluttering brightness variation as slight variations in the location of the scan lines would lead to an area being insufficiently discharged on some fields and then the excess charge being read out on later fields. In CCD pickups, the moire problem is reduced by reading out rows of pixels in pairs, i.e, on field 1 rows 1&2 are combined, 3&4 are combined, etc., and on the field 2 lines 2&3 are combined, 4&5 are combined, etc. - so again, the whole device is discharged in one field, even though there is a 1-line offset between fields.
Regarding viewing in a dark room: there is a SMPTE standard somewhere, I believe, for monitor viewing conditions, and large broadcast organizations have standard control room illumination specs also. The typical spec is to have no direct light on the face of the CRT, and the picture surround illuminated to a dim neutral value (say 10% of picture highlights? - I don't recall the exact spec). The "no light on the faceplate" rule is less important with modern low-reflectance displays - some LCDs are so good that it is irrelevant since they still appear black even with very bright light falling on them. However, the rule of viewing with dim SURROUND still applies, since this is the condition under which the tonal rendition is judged at the studio. Regarding high-def lenses, there definitely are such things. Lens designs involve such severe tradeoffs of various parameters that it is very difficult to maintain good image quality with the huge zoom range that is available in current video lenses. The tradeoffs are not only various types of distortion, but important practical things like size and weight. So, a lens that is good enough for standard def may be seen to be deficient under some conditions with a high def camera. There also has been a great change in designs for CCD cameras compared to tube cameras. In the high-end tube cameras with high end lenses, the lenses actually contained circuitry that reported the lens settings to the camera, which then adjusted the scanning to compensate for the lense distortions. Now that cameras use CCDs, that compensation is not possible (at least not without some very difficult real-time digital interpolation). Hence, extra care is needed in the design to maintain low distortion at all zoom and focus settings.
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#34
12-07-2006, 12:19 AM
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see! :P
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#35
12-07-2006, 12:47 AM
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I could be misunderstanding but
I think what was writtten by TVnut confirms the point I attempted to make which is that I expect the technology to make special lenses was perfected long ago and the lenses used in the early high end tube cameras were actually of today's technical standards.
In other words: Like many things, It was good enough by the 60's. I think there are more important things to tend to on this planet then new TV's that do the same basic thing they did in the 60's. People today get into details that do more to kill our short time in life than any percieved good.
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#36
12-07-2006, 01:02 AM
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Quote:
-Steve D.
__________________
Please visit my CT-100, CTC-5, vintage color tv site: http://www.wtv-zone.com/Stevetek/
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#37
12-07-2006, 07:49 PM
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The signal specs for NTSC have never been changed, that is, the I,Q and Y signals have the same range they have had from the beginning. So, existing signals will drive a '53 color set to its full range. However, IF the camera has been matrixed for modern phosphors, it will drive the '53 set to full range on the wrong colors. Example 1: An NTSC-matrixed camera sees a yellowish green (the same as the modern phosphor) - it doesn't produce full G-Y drive,or full (negative) R-Y in the '53 receiver, since it knows the color should be reproduced with some NTSC red in it to make the yellowish-green. Example 2: An NTSC-matrixed camera sees an NTSC-green color - it produces a full strength G-Y and (negative) R-Y and (negative) B-Y, so that pure NTSC green is produced in the '53 receiver. Example 3: A camera matrixed for modern phosphors (essentially a HDTV or PAL camera) sees a yellowish green (equal to the modern phosphor). It produces full strength color difference signals in the '53 receiver, since it is expecting to produce pure yellowish green from the modern phosphor - but the '53 receiver is driven the same way, producing the (wrong) pure NTSC green.
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#38
12-07-2006, 09:42 PM
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Pete, you are just going to have to get yourself a TK41 camera (and the room full of equipment to support it!
__________________
John Folsom
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#39
12-07-2006, 10:27 PM
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me first
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#40
12-07-2006, 10:41 PM
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Quote:
 Could this quest be a near miss?: As in Wayne's example 3 above, the OTA transmitter is capable of transmitting it, but the camera source isn't '53 NTSC, so that doesn't quite fly. Ed's method uses a high-quality vintage recording of a program shot with TK-41's, but it's not going to be transmitted OTA, so the Radio Shack, or whatever, video modulator [DVD -> RF MODULATOR -> CT-100] is unlikely to match a broadcast transmitter spec-for-spec. Also in question is the capability of a DVD (ostensibly the source of TK-41 based video) to reproduce the original vintage video accurately. I'm thinking of VHS tape. As popular as it was, it doesn't reproduce NTSC in all its glory. What about a DVD though? It's capable of greater resolution than the NTSC standard, so perhaps it can deliver true '53 NTSC color as well. Hopefully, all the issues are minor and won't aggregate into visible distortion.
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Linear Mode
