Color Test Patterns

[dtvmcdonald]

These are images I use is setting up color sets, with a special emphasis on sets using I-Q demodulation such as the CT-100.
You put these on a DVD-ROM or a USB stick and play them on your modern DVD or Blu-Ray player that does jpegs.
My player's native file size is 720x484 so that's what they mostly are.

The first set are especially useful with a scope looking at I, Q, R, G, and B
lines as they are full screen vertically.

The ones with gray background are constant Y so on the screen visually they should be pure gray with "Color" at zero or/and the fine tuning well detuned.

The next one can be used visually or on a scope. The levels are 0 for the background, from top to bottom and left to right:
255 170 85 43 128 213
The average of each line is constant luminance.

[dtvmcdonald]

The following are for visual use. The first is a modified version of a standard pattern used with a blue
filter to set "color" and "hue". The modifications allow
using red and green as well. It also has I and Q bars. The color bars are not
up to full luminance. They are 100% saturation. The long white bar is 100% luminance.

The second one has the same purpose as the first, except at variable luminance,
the brightest being full luminance RGB.

The next three are convergence and linearity patterns

The last is a special test for I-Q sets to determine if the Y and I delay lines are proper to match
the timing of Q.

[dtvmcdonald]

The last one is a test image for 15GP22s. The magenta balls at upper left and
lower right can never be gotten right with a weak red gun. Compare the TV to your computer monitor or calibrated modern TV.

Merry Christmas and a Happy New Year.

[Titan1a]

Merry Christmas to you and all Videokarma users!

[old_tv_nut]

Thanks! Will definitely add them to my collection.
BTW, the wreath may be useful for any set using a 21AXP22 also, except that RCA had already gone away from illuminant C white point; so expect a more cyan rendition (bluer on the magenta balls).

[Electronic M]

This will be useful on my 21CT55 and eventually my CT-100 once I complete the half ass resto it came to me with and replace all the 6AN8s I pirated to get the 21CT55 going.

[Hawkwind]

Nice!

This pattern is used as my desktop background on all my computers...

[old_tv_nut]

Originally Posted by Hawkwind

Nice!

This pattern is used as my desktop background on all my computers...

I would use color bar wallpaper for my desk top for nostagia's sake, but since my other hobby is photography, I can't tolerate the after-images anything colorful produces when working on my photos.

[W.B.]

Here is a twist on an old test pattern, albeit with the colors in the I, Q, R-Y, B-Y, (G-Y=0) and G-Y matrices. Hope those of you who test things get something out of it.

[old_tv_nut]

Originally Posted by W.B.

Here is a twist on an old test pattern, albeit with the colors in the I, Q, R-Y, B-Y, (G-Y=0) and G-Y matrices. Hope those of you who test things get something out of it.

Could you please identify which segments are which?

[W.B.]

Originally Posted by old_tv_nut

Could you please identify which segments are which?

I think I can help. The I and Q matrices are on the outer quadrants (-I / +Q left, +I / -Q right), the inner quadrants are:
- Top left: R-Y
- Top right: G-Y=0
- Bottom left: (G-Y)
- Bottom right: B-Y

If my cards are played right, they should be at 40% color saturation.

[old_tv_nut]

Originally Posted by W.B.

I think I can help. The I and Q matrices are on the outer quadrants (-I / +Q left, +I / -Q right), the inner quadrants are:
- Top left: R-Y
- Top right: G-Y=0
- Bottom left: (G-Y)
- Bottom right: B-Y

If my cards are played right, they should be at 40% color saturation.

Thanks.

I calculated the NTSC Y signal for a few of them from the R,G,B values indicated in the Photoshop color picker, and it comes out to 126 for all that I checked. Good start. (Probably 127 would be ideal.) In other words, the Y signal is 126 ~= 0.5/1.0.

However, for 40% saturation, it seems to me that the smallest of R, G, or B should be 60% of 126, that is, 100% saturation occurs when the smallest just goes to 0 x 126 =0, and 40% saturation occurs when the smallest is 60% of the Y signal, = 76.

However, the value of the smallest of the primaries in this pattern varies from color patch to color patch, so it seems to me the saturation is not consistently 40%.

[W.B.]

Originally Posted by old_tv_nut

Thanks.

I calculated the NTSC Y signal for a few of them from the R,G,B values indicated in the Photoshop color picker, and it comes out to 126 for all that I checked. Good start. (Probably 127 would be ideal.) In other words, the Y signal is 126 ~= 0.5/1.0.

However, for 40% saturation, it seems to me that the smallest of R, G, or B should be 60% of 126, that is, 100% saturation occurs when the smallest just goes to 0 x 126 =0, and 40% saturation occurs when the smallest is 60% of the Y signal, = 76.

However, the value of the smallest of the primaries in this pattern varies from color patch to color patch, so it seems to me the saturation is not consistently 40%.

You might have guessed that this was formatted with the black levels at 16 and the whites at 235 . . .

[old_tv_nut]

Originally Posted by W.B.

You might have guessed that this was formatted with the black levels at 16 and the whites at 235 . . .

Oh - thanks

[old_tv_nut]

Ok, I calculated the visual brightness of every color as 126, using the NTSC factors of 0.3 for red, 0.59 for green, and 0.11 for blue.

However, this means that you had to adjust the Y signal level according to hue, since if you are presenting a bluish color, as the saturation (level of chroma signal) increases, the brightness of light on the screen gets lower because the blue increase contributes 11% of its beam current increase to optical brightness, while the red takes away 30% of its electrical decrease and the green takes away 59% of its decrease. Thus, the optical brightness should be below 126. Forcing the optical brightness to be 126 means that you must be changing the Y electrical signal from its original value of 126.

So, for the B-Y case, for example, the blue value has increased greatly, being much more than 40% of the way from 126 electrical value towards max. The opposite is true for greenish colors.