RCA 21CT55 B8802897 is Alive!

[miniman82]

Originally Posted by Tomcomm

The 21FBP22 sure is bright, no problem with room lights. The reds are closer to CT-100 then most TV I've seen.

The FBP/FJP tubes have an orange-red color to me, while the earlier ones were closer to actual red. Placed side by side showing the same color bar pattern, my CTC-7 with CYP tube gets closer to actual red than the later Philco with FBP does. Since I just got a good AXP for the CTC-4, I can confirm that the AXP gets even better (what I would call more accurate) color than the CYP but at reduced brightness.

Sometime in the future I'll be doing a full writeup of all 3 tubes, so people can see the actual differences. It's slight, but perceptible.

[Tomcomm]

That quote was from Jan 08. At the time I had only observed a live 21AXP22 from 1965 when I replaced it with the present 21FB22A. the AX was so dim that I was overwhelmed with the FB brightness I didn't ponder the red purity of either. In 2008, the red purity of the FB was clearly better that all my "modern" TVs but that was due to their orangeish red Sempti phosphors in general use. I have not directly viewed a CT100 but pics posted by Pete D had reds almost identical with my 21FBP22A. Point of interest, my FB has a llight gray denergized screen while my spare FB is green. I'm assuming the gray FB in use is a "rare-earth" which has supposedly better reds than the sulfide green screen?

[Tomcomm]

Originally Posted by miniman82

The FBP/FJP tubes have an orange-red color to me, while the earlier ones were closer to actual red. Placed side by side showing the same color bar pattern, my CTC-7 with CYP tube gets closer to actual red than the later Philco with FBP does. Since I just got a good AXP for the CTC-4, I can confirm that the AXP gets even better (what I would call more accurate) color than the CYP but at reduced brightness.

Sometime in the future I'll be doing a full writeup of all 3 tubes, so people can see the actual differences. It's slight, but perceptible.

To be truly objective, you must include the gray screen 21FBP22A rare-earth. I wonder how many VK members have operating gray screen 21FBP22A's? Hopefully they also live near you and are willing to participate. How many flights of stairs did you say you had, three as I recall. LOL!

In the meantime I would like you to retake and post the 3 tv cluster pix you have. This time put the Sony closer and adjust the TVs for most accurate red and white color bars. Also pull-in to include only the TVs and shoot in total darkness. I have been playing with the color balance feature of my Photo Impact graphics program that reads the RBG values 0 to 255 of any spot on the JPG image. This is the hacker's approach to chromatic spectrum analysis but should give quantified data on relative phosphor differences of all your CRTs.
Thanks for your interest and cooperation.

[miniman82]

Originally Posted by Tomcomm

In the meantime retake and post the 3 tv cluster pix you have.

Hopefully I can get the 21-CT-55 up and running soon, then I will have a pic with a modern monitor, 21CYP22, 21AXP22A (grey), 21AXP22 (green), and green face 21FBP22.

[Tomcomm]

Originally Posted by Tomcomm

To be truly objective, you must include the gray screen 21FBP22A rare-earth. I have been playing with the color balance feature of my Photo Impact graphics program that reads the RBG values 0 to 255 of any spot on the JPG image. This is the hacker's approach to chromatic spectrum analysis but should give quantified data on relative phosphor differences of all your CRTs.

I have now performed the above Photo Impact “spectrum analysis” on some of my 21CT55 screenshots verses ’84 Sony pro monitor and ’97 Sony 27in tv. All pics were shot with the same Canon S40 and were not color enhanced. I used the DVE color bar for all screenshots tests and “normalized” each pic by placing the virtual sampling probe onto each white bar and setting the brightness to produce approximately the same digital 255 max red, green and blue components. I then placed the sampling probe onto the red bar and took digital readings of its red, green and blue components. Ideally, a perfectly pure red bar should produce a red component of 255 while its green and blue components should read zero. Only the color accuracy of the Canon camera sensor is evolved here since the LCD computer monitor’s color accuracy is never an issue. Since relative CRT phosphor chroma response is all we are interested in, any variance of these readings indicates contamination of the ideal red phosphor’s light output, right?

Preliminary estimates of red phosphor purity of a ’88 13in Sony pro monitor, a ’97 27in Sony "modern" tv and of course the 21CT55 with 21FBP22A “rare-earth” crt follows:

21in FBA.……………Red contaminated with 5.6% green and 8.2% blue
13in Sony……………Red contaminated with 12.6% green and 6.3% blue
27in Sony……………Red contaminated with 29.2% green and 21.3% blue

No wonder the “modern” TV crts appear orangish red!

[old_tv_nut]

Originally Posted by Tomcomm

21in FBA.……………Red contaminated with 5.6% green and 8.2% blue
13in Sony……………Red contaminated with 12.6% green and 6.3% blue
27in Sony……………Red contaminated with 64.2% green and 53.3% blue

Those numbers for the 27 inch Sony should correspond to a visually washed out red - something is not right with those numbers, unless you report that visually it appears that bad.

In regards to "the red bar color should normalize to (255,0,0) RGB," I'm afraid it just ain't so, for a whole slew of reasons: the impossibility of getting ideal filters in the camera, the different spectra of the displays that interact with the filters in the camera; the raw to jpg conversion in the camera having a matrix that is designed to give pleasing color, not accurate color; deliberate non-linear S-curve processing in the camera to mimic the pleasing contrast response of film; etc. etc. etc. etc.

The human eye is a much better instrument for these comparisons than a digital camera.

[Tomcomm]

Wayne, thanks for the reply. I reran the 27in Sony by brightening the white bar. It was way too dark before which caused the red bar to saturate and as you said, "wash-out". The new results:
21in FBA.……………Red contaminated with 5.6% green and 8.2% blue
13in Sony……………Red contaminated with 12.6% green and 6.3% blue
27in Sony……………Red contaminated with 29.2% green and 21.3% blue

Somewhat less contaminated but still way orangish red compared to the Sony pro and the 21CT55 with 21FBP22A. The stated 255,0,0 RGB was "ideal" with no hardware limitations. I believe this simple and cheap method of relative phosphor comparisons can be quite useful when comparing the original NTSC rated crts eg 15GP22 and 21AXP22 with the gray screen 21FBP22A. All I need is optimally setup color bar screenshots of the original GP/AXPs. I don't have much hope for a live eyeball shootout that includes the gray screen 21FBP22A, certainly not one I may witness.

[old_tv_nut]

Originally Posted by Tomcomm

Wayne, thanks for the reply. I reran the 27in Sony by brightening the white bar. It was way too dark before which caused the red bar to saturate and as you said, "wash-out". The new results:
21in FBA.……………Red contaminated with 5.6% green and 8.2% blue
13in Sony……………Red contaminated with 12.6% green and 6.3% blue
27in Sony……………Red contaminated with 29.2% green and 21.3% blue

Somewhat less contaminated but still way orangish red compared to the Sony pro and the 21CT55 with 21FBP22A. The stated 255,0,0 RGB was "ideal" with no hardware limitations. I believe this simple and cheap method of relative phosphor comparisons can be quite useful when comparing the original NTSC rated crts eg 15GP22 and 21AXP22 with the gray screen 21FBP22A. All I need is optimally setup color bar screenshots of the original GP/AXPs. I don't have much hope for a live eyeball shootout that includes the gray screen 21FBP22A, certainly not one I may witness.

This is still a little suspicious. Getting purer colors when the drive is turned up could indicate that the black level is a little high or there are reflections of room light. This would be a valid test of how the tube is set up and viewed, but not necessarily the characteristics of the red phosphor color alone. To get the comparison of the pure phosphor colors you need to do two things:
1) take the picture in a completely dark room, making sure there are no reflections (like from your shirt)
2) turn up the color control and adjust the tint if necessary to make sure only the red beam is on and the other two beams are completely cut off.
2b) Since the color demodulator may include color corrections that deliberately make the primary bars impure, you may need to readjust the tint individually for each primary color if you want to measure the green and blue also.

[Findm-Keepm]

Originally Posted by Tomcomm

Only the color accuracy of the Canon camera sensor is involved here since the LCD computer monitor’s color accuracy is never an issue.

Wouldn't the kelvin temp of the LCD monitor backlights be an issue, or is that somehow compensated for/already calibrated/or not an issue?

Mind you, I'm a amateur with all of this, but my two LCD monitors have two Kelvin settings that affect the color spectra - 6500K (default) and 9300K.

Interesting thread! I've worked TV's for 30+ years and about all the discussion I've ever heard is from a old, now-dead TV tech that swore by the "old" RCA red versus the "new" RCA red. I guess he too would've been interested in this thread.

I'm learning, keep posting!

Cheers,