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  #46  
Old 10-31-2005, 07:53 AM
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That's still a truly GORGEOUS picture any way you cut it-Man, I wish I'd scored a CT-100 back about 20, 25 yrs ago when they were just junky old TVs....-Sandy G.
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  #47  
Old 10-31-2005, 12:14 PM
frenchy frenchy is offline
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I have been in the back bedroom doing final adjustments of my CTC-10 and was flipping around and noticed that South Park also (now it's on free tv), I think I'll watch it again and see what the dude's hat looks like! (ok it's not a 100 but oh well I'll take what I can get ; )
You should send these pics to the creators of SP and tell them this is what their cartoon ACTUALLY looks like : )
Frenchy
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  #48  
Old 10-31-2005, 10:04 PM
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Most digital still cameras use the sRGB gamut (same as HDTV), and computer monitor primaries are similar, so showing what the sets actually look like to the eye will be a problem (although you should be able to see a difference of some kind in photos of the two screens).

Years back, a SMPTE monitor committee had two identical tubes made up (by Sylvania, IIRC) except for the green phosphor, one sulfide green and one NTSC green.. They were mounted in identical monitors and set up in the engineering lab studio at NBC in New York. They had some brightly colored objects in front of the camera including something "Kelly green". With this setup you could clearly see the difference, not only in the greens, but in the cyan saturation and the relative brightness of cyans and reds. They eventually demonstrated that you could get reasonable/acceptable (though not perfect) rendition of colors within the sulfide gamut by changing the matrix in the monitor. As a result, future monitors (Like the Tektronix Trinitron-based series) had a switch to turn the matrix adjustment on and off. You would set up the hue and chroma on color bars with the switch off, then turn it on to get reasonable flesh tones.
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  #49  
Old 11-01-2005, 05:15 AM
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Pete Deksnis Pete Deksnis is offline
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SMPTE changes

Quote:
Originally Posted by old_tv_nut
...you could get reasonable/acceptable (though not perfect) rendition of colors within the sulfide gamut by changing the matrix in the monitor. As a result, future monitors (Like the Tektronix Trinitron-based series) had a switch to turn the matrix adjustment on and off. You would set up the hue and chroma on color bars with the switch off, then turn it on to get reasonable flesh tones.
Wayne: Did the capability of the broadcast industry to transmit NTSC gamut shrink with the advent of SMPTE standards?

Or, is it possible — maybe even likely — that the difference in green between the HDTV and CT-100 I saw is a lucky confluence of NTSC-gamut-capable broadcasting plus an overly enthusiastic graphic artist? Rather than some Pete eye-brain quirk!


Also, I won’t be content making CT-100 matrix adjustments using a DVD and a VCR modulator. I suspect that my best chance at a calibrated NTSC-modulated color bar signal is an over-the-air signal.

At one time, broadcasters around here transmitted color bars after they signed off. Nobody seems to sign off anymore. But I found Ch. 13, the PBS station, did so at three a.m. last weekend and transmitted over-the-air color bars.

But I slept right through it. So this weekend if they repeat the bars I’ll try again and use the R and G and B filters that come with Video Essentials to check the two sets. Which brings up another point. I didn’t see any traceable calibration stickers on the color filters…
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  #50  
Old 11-01-2005, 08:34 AM
3Guncolor 3Guncolor is offline
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Pete,
Try to give the engineering staff at the PBS station a call. I’m sure there’s a good chance once you tell them what you are doing and why they may help you in some way. At the very least they may tell you when they are going to have color bars up.

Great Picture

Good luck
Steve
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  #51  
Old 11-01-2005, 08:44 AM
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Pete,

The question of what you should see on today's NTSC transmission is almost unanswerable. The taking characteristics (spectral response) of cameras is not an ideal match to the human eye to begin with (just too difficult to do). Major design criteria are a proper red/green crossover to get flesh hues right, plus a matrix to match the expected monitor primaries generally. Camera designers can do a mathematical calculation of the camera's performance based on a set of color chips, like the Macbeth ColorChecker chart, and adjust the camera matrix to match NTSC. But they would be foolish to not check it on a modern monitor. So, do current cameras and film scanners match NTSC best, or are they tweaked towards current monitors? I don't know, and I don't know that camera makers release this info - they sell cameras based on price, features, and how good they look in a display studio at the NAB convention. Beore blamng the camera guys for tweaking, consider that consumer receivers wiht non-NTSC phosphors have had a wide variety of matrix fiddles to make their rendition closer to NTSC (like the professional monitor matrix I wrote about). So, the system in the US has essentially been out of control.

Now, if you ask about PAL, the answer is simple: PAL standardized on the non-NTSC phosphors and specified their colors precisely, so they cannot transmit colors out to the NTSC gamut. HDTV is the same way - smaller gamut, but precisely defined.

Older material made with image orthicon cameras is intended for NTSC phosphors, but those cameras had no matrixing, so they are the best you can get with optical filtering only. Like most color film, they increased saturation by using narrower than theoretical R,G, and B filters, reducing the need for the matrix.

I was going to say that using the DVD and modulator should not be a problem, but it depends on the modulator having the proper R-Y and B-Y gains, and I suppose they might be wrong (although I think it's unlikely). A video tape of the color bars off your local station should work, since the tape shouldn't affect the R-Y and B-Y differently.

What local station is that? If you got through to the chief engineer and told him what you're doing, you likely could talk him into putting up the signals you want -especially if you invited him over to see the result.

The main requirement for the video essentials filters is that each one suppresses the other two primaries well enough that they don't affect your judgement - so traceable calibration is not needed, just a deep enough color. You should be able to tell if the red filter is letting any green and blue through by looking at the green and blue bars, and so on.
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  #52  
Old 11-01-2005, 11:20 AM
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Thanks guys. You've given me plenty to consider.

On another note, recall the label on the CT-100 shows 475 watts at 115 Vac as the power used by a Merrill.

Just measured it. With a 115 Vac line, the unit draws 415 watts with a PF of .85, which measures/calculates out at 485 VA / 488 VA. So in conventional terms the draw is more like 415 watts.
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  #53  
Old 11-07-2005, 12:32 PM
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thank god AK is back ... was gettin' the shakes.

Quote:
At one time, broadcasters around here transmitted color bars after they signed off. Nobody seems to sign off anymore. But I found Ch. 13, the PBS station, did so at three a.m.
Checked o-t-a colorbars early this morning. Couldn't see a difference between over-the-air bars or the same station received via cable.

Checked also the HDTV versus the CT-100 after setting both using R, G, and B filters. The green test looks better on the CT-100 and was able to demonstrate it for the site; the other colors test pretty much alike between the two sets. Here's a link:
http://home.att.net/~pldexnis/input/...ntresults.html
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  #54  
Old 11-07-2005, 06:48 PM
frenchy frenchy is offline
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To my eyes the yellow on your hdtv looks more 'yellow' than on the ct-100, which looks lime-greenish. Anybody else? Funny that's like the same color area that South Park hat is in. But I'm not looking at them directly, I'm just looking at pics of them on my monitor so....
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  #55  
Old 11-07-2005, 07:46 PM
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Last edited by andy; 12-07-2021 at 02:29 PM.
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  #56  
Old 11-08-2005, 09:48 AM
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Quote:
Originally Posted by andy
Was that HDTV receiving an ATSC signal, or an NTSC signal? If it was NTSC, a lot of the problems you see could be caused by the sets digital processing.
Both NTSC. When receiving analog broadcasts, ATSC sets I'm familiar with (not many) don't seem to equal a modern analog set such as the CTC169 series. I'm guessing the HD set matrix is responding the way it was designed. Jeff Landaro designed the video amp in that set; maybe he's available for an inside expose

The lime-green on the CT-100 Frenchy mentioned had been a problem for me too, although since the matrix balance was improved for red, the yellow no longer seems 'off' when viewing the screen. Probably attributable to the strong/wide-gamut green of the 15G.
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  #57  
Old 11-08-2005, 11:52 AM
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1) your mono picture of the big set shows less green on the yellow bar, so you would expect its yellow to be less green
2) The red looks darker and the blue looks brighter on the CT100 than on the large screen. The yellow looks greener and the magenta looks bluer. I would check the white point (blue and green drive settings) on the CT-100. If your white is lacking in red, that could be part of the difference. Ideally, you should have a gray background wall in the room lit by daylight or artificial daylight to compare to, or at least be able to look outside at daylight for comparison. Anyway, in turning idown the green and blue drives, it helps to go too far (slightly pink whites) if you can get there, then return to a neutral white, rocking the controls back and forth while you zero in on the neutral point.
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  #58  
Old 11-08-2005, 12:40 PM
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Pete Deksnis Pete Deksnis is offline
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Quote:
Originally Posted by old_tv_nut
If your white is lacking in red, that could be part of the difference. Ideally, you should have a gray background wall in the room lit by daylight or artificial daylight to compare to, or at least be able to look outside at daylight for comparison.
It might take a few days, but I'll readjust the B and G drives as per your suggestion; saw a D6500 fluorescent work light at Sears; bought it and have it behind the HDTV a la Digital Video Essentials. BTW, when a 100-percent red screen is applied to the CT-100, it swamps something and shows a dark mustard-yellow, although the 75 percent red is red and at least 'looks' okay. It's all about red in a CT-100 I guess. Back in the '60 when I last fiddled with a Merrill, never had this much fun nor learned so much new stuff about it.
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  #59  
Old 11-11-2005, 05:34 PM
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Fantastic reading.You've done a marvelous job in resurecting this set.

My comment that follows is mearly a suggestion.If you're unfamiliar with adjusting gray scale,I thought I might pass on some basics to help.

From some of the pictures you've attached do show that your gray scale is off on both ends.This may be just the pictures,but if what is shown is what you're seeing on the set when looking at the stairstep pattern,it looks to me as if both ends are off.That pattern should show shades of gray from black to white when properly calibrated.It looks bluish on one end and greenish on the other.If you're trying to approach the NTSC color temperature of D65 (6500K),what will help is a colorimeter.Doing it by eyeball is impossible.Prior to any adjustments to these areas,it's imperative that the Black and White (brightness and contrast) levels be adjusted properly.

There are two different adjustment points,the lower end using a 20IRE window pattern and the upper end using a 100IRE window pattern.Most sets have these controls,whether it be by analog pots pots or by service menu access in the newer digital sets.The lower end controls are called cut or bias or even screen by some manufacture while the upper end controls are called drive.If you have R G B for both end,great.Some sets only have two,just depends on the manufacture.

A bias light behind the tv or screen is not a reference for D65 adjustment puposes.It's there for overall viewing reference.

I've had the opportunity to calibrate a few CRT direct view sets and projectors over a span of about 6 years,using a Philips color analyzer and test pattern generator.Have also used patterns from A Video Standard and Video Essentials.The patterns from VE are very good.Getting the gray scale to track properly isn't always easy nor do sets hold them well.But,if this can be done,then the set's color will be as true as it can be,without being shaded.

Please do not take any of my comments or advice as criticism.On the contrary,I am just ecstatic to see life being brought back to these sets.I remember them fondly and have always been fascinated by television.I don't have the repair background that you obviously posses,but my curiosity as to why they all looked different pushed my desire to learn as much as a hobbiest/part time member of ISF could with respect to picture quality.
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  #60  
Old 11-11-2005, 06:49 PM
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Pete Deksnis Pete Deksnis is offline
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I agree with what you say about using instrumentation to set grey scale. Actually, I have never had the advantage of being a TV repair technician. For most of my work life I was an editor of one type or another. But I’ve also had opportunity to make a living troubleshooting to component level and have spent a few years working with instrumentation including initial power-on thru final calibration. All this is in support of my first sentence.

I’m going to check eBay; perhaps a reasonably priced colorimeter still in acceptable calibration will turn up.

Some things I’ve grown to acknowledge and appreciate recently are issues that effect stability of this restored Merrill. My feeling is that it’s a result of the original design rather than some artifact of age or the restoration process. In discussing this with John Folsom, who of course is a premier collector of 15-in. vintage color, it seems that most vintage sets are fickle, but the Westinghouse H840CK15 is far more stable than the CT-100, particularly in the area of high-voltage regulation, which I find, in the CT-100, is apparently an issue in an attempt to achieve brightness suitable for a desired, wide, grey scale.

Another area that’s been challenging when adjusting the matrix is to achieve a toned-down green component in the color bar display. It’s well known and fully appreciated that the red phosphor in a 15GP22 is by far the least efficient. I expect to work more on these challenges this weekend, but perhaps there’s just not enough latitude in the red to overcome the brightness and more importantly perhaps, the very wide green gamut, when adjusting grey scale (as you say, 20IRE to 100IRE) before trying to get eyeball-perfect color bars.

As I said, never had hands-on TV repair experience or did I ever work in broadcast video, so much of this detail stuff is new to me. Add to that the fact I’m an old guy….

Appreciate all the comments and suggestions received along the way. In particular, Old_TV_Nut with all his envious TV-engineering experience who kindly nudges me in the right direction now and then.

Have attached a shot taken this morning of simultaneous ATSC-NTSC broadcasts. The two ends of the engineering spectrum match fairly well in this shot, but I’ll admit to toning back the HD set in brightness and contrast a bit.
Attached Images
File Type: jpg CT-100-atsc-ntsc-GMA.jpg (74.1 KB, 53 views)
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