NTSC Pennant?

[Phil Nelson]

Cool. How did you do color correction? I'm a dolt when it comes to using Paintshop. I have the original scan (820K !) at http://antiqueradio.org/art/temp/NTSCBackground.jpg .

Phil

[Joel Cairo]

Wow-- thanks for supplying the original scan, Phil!

I've similarly color corrected the original (as well as did a quick bit of clean-up to even out the lighter blue on the right, and get rid of a few dark spots and image flaws), and reduced it to the same 1024 x 599 size. The reduction route gives much nicer results than blowing up a small image, since the final picture retains a lot of the texture of the original, which my blow-up wouldn't have had, even if it were sharpened.

Looks decent enough, I'd say...

-Kevin

[Phil Nelson]

That's much better. It's already on my desktop. Thanks!

Phil

[wa2ise]

Did a little photoshopping

And the digital version as well

[W.B.]

It seems, based on the colors as registered in this JPEG file, that 205° would be the RGB position for -I, 24° for +I, 275° for +Q and 95° for -Q, would that sound correct? (Being that RGB values are different from the phase positions in video language.) I had done my own research of position values in Photoshop and Corel Photo-Paint 11, and had come up with:
- 204° for -I
- 24° for +I
- 272° for +Q
- 92° for -Q

[old_tv_nut]

Originally Posted by W.B.

It seems, based on the colors as registered in this JPEG file, that 205° would be the RGB position for -I, 24° for +I, 275° for +Q and 95° for -Q, would that sound correct? (Being that RGB values are different from the phase positions in video language.) I had done my own research of position values in Photoshop and Corel Photo-Paint 11, and had come up with:
- 204° for -I
- 24° for +I
- 272° for +Q
- 92° for -Q

I'll have to check out the code when I get back home. This simulation was done in Photoshop by writing custom Photoshop filters to do the matrixing, chroma modulation, filtering, and demodulation, would you believe? I just love perverting software to do things I want that it never was intended to do.
By defining the +/- I and +/- Q subcarrier peaks to fall on pixel locations, modulation and demodulation can be simulated by multiplying by a pattern of
(+1,0,-1,0) or (0,+1,0,-1).

The +I channel should be at 33° electrically with respect to scaled R-Y and scaled B-Y, and the other three phases at 90° increments. You have to be careful that you are working with properly scaled R-Y (divided by 1.14 if I recall correctly) and B-Y (divided by 2.03 if I recall correctly) before converting to I,Q. The values you found may be correct when calculating angles in the RGB domain, that is, with straight R-Y and B-Y.

[W.B.]

Originally Posted by old_tv_nut

I'll have to check out the code when I get back home. This simulation was done in Photoshop by writing custom Photoshop filters to do the matrixing, chroma modulation, filtering, and demodulation, would you believe? I just love perverting software to do things I want that it never was intended to do.
By defining the +/- I and +/- Q subcarrier peaks to fall on pixel locations, modulation and demodulation can be simulated by multiplying by a pattern of
(+1,0,-1,0) or (0,+1,0,-1).

The +I channel should be at 33° electrically with respect to scaled R-Y and scaled B-Y, and the other three phases at 90° increments. You have to be careful that you are working with properly scaled R-Y (divided by 1.14 if I recall correctly) and B-Y (divided by 2.03 if I recall correctly) before converting to I,Q. The values you found may be correct when calculating angles in the RGB domain, that is, with straight R-Y and B-Y.

I found that +(R-Y) in RGB domain was 340°, while -(R-Y) was 160°; +(B-Y) was 250° and -(B-Y) [a.k.a. NTSC 'burst'] was 70°; and G-Y=0 values were 43° and 223°. I also found the +/-I and +/-Q values through taking the YCbCr calculations in color bars and changing the luma from 16 to 126.

I am aware that RGB values are different from what is registered on color vectorscopes.

[ChrisW6ATV]

Here is another scan from that same book by Bernard Grob. I didn't realize it was discussed here until I re-read this topic after randomly picking up a book on my shelf, seeing the flag in it, and remembering this discussion.



If anyone wants it, I have an 8MB 5000x3000-pixel JPEG of this version, or the original 52MB uncompressed TIFF of the whole book page.