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  #16  
Old 10-20-2007, 06:38 PM
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One of a kind

I will be 60 on Nov 5th, and I alos can remember seeing color when my dad took me to a tv store somewhere in South Bend. That image was embedded in my memory and even though I was only about 8 or 9 I was hell bent to have a color set in our house. I guess the round tube sets help revive that magical time when color seemed about as probable as Flash Gordon landing with Dr. Zarkov.

I was surprised to find other people just like me that had the same experience.
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  #17  
Old 10-20-2007, 07:31 PM
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Although color tv was not completely unknown to me, I had never seen a roundie until 1974. It was in my grandparents house. It was a 1965 Zenith console, the same model that I have although not the same set. I was fascinated by the screen shape as all I knew were rectangular sets. I never forgot it and have wanted one since that time. I only have one such set, but one is enough for me as they require a lot of space and are expensive to restore.
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  #18  
Old 10-20-2007, 07:44 PM
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As was mentioned earlier, the extra difficulties with convergence and pincushion presented by a rectangular tube were the reasons the first color sets were round, not an inability to blow a rectangular glass funnel. As for hiding 'easter eggs', I am sure they didnt. . remember, there were millions of B&W rectangular sets watching. I dont know when the technology for adding that garbage came along, but I dont recall seeing it until the eighties.
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  #19  
Old 10-20-2007, 09:48 PM
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FWIW, I have opinions and information on several things in this thread:

The scanning of the corners of the image onto the bell of the round color tubes was detrimental in another way besides content loss - the 21kv electrons would generate about 16 kv or so secondary electrons, which would scatter all over the tube face and light up all the phosphors a bit, reducing the contrast and color purity whenever there was somethng bright in the corner of the image. With the inefficient early red phosphor, which required more beam current, this meant that the green and blue lit up more with this stray light, so a pure red was harder to obtain in practice. Even though the red phosphor itself may have been a bit more saturated, depending on picture content, the blue and green were lit up somewhat when they shouldn't have been. Later picture tubes did much better at maintaining color purity and contrast into the lowlights when the picture also contained bright areas, and this was just one reason why.
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As to seeing things in the corners and edges - just play an old color show, like the last Howdy Doody show, onto a 16x9 HD set (so the left and right edges are completely visible), and you'll see plenty - plenty of misregistration, target flicker, horizontal sweep ringing, and other TK-41 camera shortcomings.
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Biggest problem with cutoff material on roundies in the old days was movie titles. these days, calbe box menus, DVD menus, etc. all extend into the roundie cutoff corners.

On the other hand, sets were too wildly variable in centering and scan size for anyone to put an Easter egg in the corner and be sure it wouldn't be seen.
The edge cut off might be anywhere from zero to 10% of the picture. Solid-state sets got more stable, but not always any better in manufacturing tolerance. A decent solid state CRT set with adjustments (like CRT projos) should not overscan more than, say, 3%, in my opinion.

As time goes by, it will be less likely that flat panel sets will need overscan; but at this point there is still a need for some, since the source material in some cases has suffered a bit of loss while in the analog domain. People are gettting used to 25% black bars when the aspect ratio mismatches the screen, but just a little black that comes and goes with source material looks like an annoying malfunction.
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Regarding old professional monitor underscan, professional color monitors always had an underscan switch. This was essential in seeing the whole image while setting up a camera for registration and proper scan on a (printed) test pattern. These monitors also had a "pulse-cross" switch that would offset and enlarge the vertical scan so you could see the vertical sync pulses and determine quickly if they were normal.
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  #20  
Old 10-20-2007, 10:03 PM
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FWIW, I have opinions and information on several things in this thread:

The scanning of the corners of the image onto the bell of the round color tubes was detrimental in another way besides content loss - the 21kv electrons would generate about 16 kv or so secondary electrons, which would scatter all over the tube face and light up all the phosphors a bit, reducing the contrast and color purity whenever there was somethng bright in the corner of the image. With the inefficient early red phosphor, which required more beam current, this meant that the green and blue lit up more with this stray light, so a pure red was harder to obtain in practice. Even though the red phosphor itself may have been a bit more saturated, depending on picture content, the blue and green were lit up somewhat when they shouldn't have been. Later picture tubes did much better at maintaining color purity and contrast into the lowlights when the picture also contained bright areas, and this was just one reason why.
-------
As to seeing things in the corners and edges - just play an old color show, like the last Howdy Doody show, onto a 16x9 HD set (so the left and right edges are completely visible), and you'll see plenty - plenty of misregistration, target flicker, horizontal sweep ringing, and other TK-41 camera shortcomings.
--------
Biggest problem with cutoff material on roundies in the old days was movie titles. these days, calbe box menus, DVD menus, etc. all extend into the roundie cutoff corners.

On the other hand, sets were too wildly variable in centering and scan size for anyone to put an Easter egg in the corner and be sure it wouldn't be seen.
The edge cut off might be anywhere from zero to 10% of the picture. Solid-state sets got more stable, but not always any better in manufacturing tolerance. A decent solid state CRT set with adjustments (like CRT projos) should not overscan more than, say, 3%, in my opinion.

As time goes by, it will be less likely that flat panel sets will need overscan; but at this point there is still a need for some, since the source material in some cases has suffered a bit of loss while in the analog domain. People are gettting used to 25% black bars when the aspect ratio mismatches the screen, but just a little black that comes and goes with source material looks like an annoying malfunction.
-----------
Regarding old professional monitor underscan, professional color monitors always had an underscan switch. This was essential in seeing the whole image while setting up a camera for registration and proper scan on a (printed) test pattern. These monitors also had a "pulse-cross" switch that would offset and enlarge the vertical scan so you could see the vertical sync pulses and determine quickly if they were normal.
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  #21  
Old 10-20-2007, 10:33 PM
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The "natural" view area of two eyes is closer to the 16:9 aspect ratio of HDTV and HD DVDs than to the shape of a round CRT.
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  #22  
Old 10-20-2007, 10:56 PM
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Quote:
Originally Posted by ChrisW6ATV View Post
The "natural" view area of two eyes is closer to the 16:9 aspect ratio of HDTV and HD DVDs than to the shape of a round CRT.
Yep. The Japanese did studies on the best frame shape for HDTV, and came up with 15x9 IIRC, later modified to 16x9 for mathematical elegance and because that was the middle of the various movie formats.

Most paintings are slightly rectangular, like maybe 1.2:1 or 1:1.2. A tall oval frame makes an elegant portrait. I wonder if round/oval paintings would be more common if round canvases and frames were easier/cheaper to make?
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  #23  
Old 10-20-2007, 11:01 PM
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sampson159 sampson159 is offline
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now that i have a picture on my roundie- i forgot what red ,blue,and green really look like! the color reproduction is movie quality.technicolor at home!i dont care about the shape,overscan ,easter eggs,etc-the picture is as i remembered back in the early 60s in downtown columbus,shopping with my dad for our first color set.the excitement and fascination of all the different models.with a cable box, the picture is flawless.i have a dlp 106 inch projector with hd hook-up in my movie room and i like my rca much better.can t wait to get started on my zenith roundie!
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  #24  
Old 10-20-2007, 11:01 PM
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By the way, this reminds me that Kenny Rogers once said he took pictures at the zoo - and the giraffes ordered a dozen 80x10's.
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  #25  
Old 10-21-2007, 12:33 AM
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Quote:
Originally Posted by kx250rider View Post
The corners are cut off by the shape of the screen, but they're still there on the edges of the glass. If you see a B&W round tube with a little bit of phosphor residue on the sides of the glass, you can actually see the corners of the picture. On a color roundie, you wouldn't be able to see the corners due to the shadow mask and other internals.

I believe that broadcasters would avoid putting anything important in the corners. Steve D might be able to elaborate on this, but I don't think they tried putting anything like icons in the corners 'til the 90s.

Charles
I recall back in the late'60's when rectangular color sets were starting to outsell roundies, our directors would still make sure pictures were framed so that nothing important was cut off on a home roundie color set. This was especially critical when producing commercials. After all there were thousands of round tube color sets in use well into the 80's.

-Steve D.
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  #26  
Old 10-21-2007, 11:25 AM
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Quote:
Originally Posted by old_tv_nut View Post
Yep. The Japanese did studies on the best frame shape for HDTV, and came up with 15x9 IIRC, later modified to 16x9 for mathematical elegance
Veddy Intaressting as Arty Johnson used to say. Didn't know what more there was to it than the 3^2 x 4^2 bit.
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  #27  
Old 10-21-2007, 04:54 PM
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Quote:
Originally Posted by Carmine View Post
As was mentioned earlier, the extra difficulties with convergence and pincushion presented by a rectangular tube were the reasons the first color sets were round, not an inability to blow a rectangular glass funnel.
I think a rectangular screen's surface is "spherical" just like a round screen's one... the only real difference is the shape... early rectangulars also had more or less the same curvature radius as roundies...

actually, one could say that a 21 inch rectangular screen is just a cut out section of a larger 21 inch round screen

i don't think the difficulty into making a rectangular screen is a matter of pincushion corrections, it's more likely a matter of easier shadowmask and phosphor dot screen construction...

The real challenge with pincushion correction and convergence came out with 110 degree color CRTs, earlier 90 or 70 degree tubes were much easier to drive... and for this very reason many late cheap sets are going back to 90 degree CRTs...
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  #28  
Old 10-21-2007, 08:59 PM
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Quote:
Originally Posted by Kiwick View Post
I think a rectangular screen's surface is "spherical" just like a round screen's one... the only real difference is the shape... ..
True in part, but there are a whole bunch of considerations -
Corner convergence;
Bulb strength;
Corner purity - which is related to brightness gradation:
To make obtaining purity easier, the shadow mask holes (or equivalently, the black matrix holes) were made smaller towards the edges. This was done so strongly on some rectangular designs that people complained that there was a bright area in the center of the picture (this was not a sharp-edged area, just the gradual variation from center to edge). Due to the lack of low-frequency response in the human visual system, you can get away with some of this, especially when the picture is viewed up close - but from far away it's more noticeable.

Later tubes were designed with flatter faces, making all the problems more difficult.
By that time, stripe screens had replaced dot screens, allowing self-converging yoke designs. Since vertical beam angle does not affect purity on a stripe screen, that degree of freedom can be used to help get convergence, and the convergence circuits can be eliminated.
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  #29  
Old 10-22-2007, 04:01 AM
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Some early 70s 110-degree In-line CRTs like Toshibas, the GTE-Sylvania Uniline, and the Philips 20AX weren't self converging, they still had convergence coils on their necks and required a convergence circuit with lots of adjustment knobs just like delta gun CRTs...

Self converging "Precision in line" tubes (RCA) which were the first to do away with any kind of convergence circuit in the mid-late 70s, had a finer stripe pitch in the center of the screen, and a quite coarse pitch at the sides, unlike earlier inline CRTs which had a constant stripe pitch all over their screen

as for bulb strenght, the real challenge was posed by early 110-degree B/W CRTs, as the flatter bell and increased vacuum would put a lot of strain on the edge of the screen, so early 110-deg tubes were very fragile and dangerous, but by the time the first 110-degree color CRTs came out in the late 60s, the "tensioned rimband" integral implosion protection had already been invented.

In fact, a good CRT (both 90 or 110 degree) with a serious tensioned rimband is extremely safe, and does away with the need for bonded lenses or separate safety glasses... actually, you can't get one to implode even if you smash it with a hammer... it will just break where you hit it and quietly lose the vacuum through the hole.
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  #30  
Old 10-22-2007, 12:12 PM
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Hey: Old_TV_Nut's avatar roundie is changing pictures every few seconds! Neatest thing I've seen on an avatar! How'd you do that?

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