So which color is correct? (VBXE+GBS 8220 vs Altirra)

[leech]

So I've been trying to tweak the colors for hours on my upgraded 130XE. I've compared the colors to the S-Video output, VBXE output and Altirra. Granted the other two outputs are on the same Dell 2001FP monitor, where Altirra is running on the Dell S2716DG. But that dark green color certainly doesn't look like 'Rust' to me!

 

I've played with the POT on the 130XE itself (though I think that only affects the normal Composite/S-Video output?) and then with them on the GBS-8220, and I thought I got all the colors right, then did a comparison with Altirra and.. nope!

 

I could do more pictures if people ask. Helps if I specify. Left is the physical hardware. Though you can see my icons and such in the background of the right picture... I can do a video capture on the same screens later, if people think it's a color profile thing.

Edited November 6, 2017 by leech

[Rybags]

Colour adjustment best done with a display showing at least the 16 base colours.

There's programs around that show 128 or 256 colours as well.

 

Colour is a matter of preference sometimes. And will be different between Pal/NTSC.

VBXE uses a modified LAOO palette and probably more oriented towards looking better than accuracy. For starters the overall saturation is better.

[phaeron]

VBXE uses an RGB palette inside of the core, laoo.act. This is a PAL palette and thus you would see PAL colors even on NTSC. In particular, colors 1 and 15 will be orange instead of the colors you would see on NTSC. The color pot also won't do anything. The GTIA core allows the default to be changed, but the FX core requires any desired palette changes to be uploaded post-boot by software. This means you could change the VBXE palette to whatever you want, though you'd have to upload it on every power-up with the FX cores.

 

Note that Altirra's VBXE emulation sets palette 0 to the global color settings instead of laoo.act, so you will see different colors in emulation. This is to avoid disabling the global color settings when VBXE is active, and frankly forcing PAL colors in NTSC mode is wrong.

 

You should calibrate colors while looking at all 256 colors instead of trying to match colors by name -- darker colors can have significant color shifts due to clamping negative color and there is a lot of variance in naming colors. If you need such a program, you can use colormap.com from the Additions.atr disk image that comes with Altirra.

 

[_The Doctor__]

the Atari needs to be on at leat 15 minutes before adjusting and it is best to use more than one color bar program to do so... please read about the two ntsc standard and know what chip is in your Atari.... you said 130xe SO I assume the later second standard... truly know what the color 'goldenrod' is if you know that you can adjust accordingly... especially if you have a paper with the true goldenrod color on it... eyes drift in perception and a reference is needed by most people..

 

emulators have more than one palette to choose from ... make sure you have the right one loaded for the selected chipset...

 

shortcomings for NTSC is why I will not own a VBXE it has problems...

Edited November 6, 2017 by _The Doctor__

[leech]

Ah,the color profile for emulation makes sense. Any suggestions for something that shows 256 colors?

 

I actually have a spider color calibrator, not sure how useful that would be in this case. Speed badly since I was not too impressed with it previously. Always seemed to make things too dark.

[_The Doctor__]

I've heard that before, usually brightness won't make the color drift much once you calibrate so while it might be dark once you brighten it's pretty darn close.... some displays won't give a good black without cloud or inky blueness so the calibrator goes too far in darkening the screen...

 

as for the palette, Altirra has separate ntsc and pal palettes switch see what one works best... I haven't messed with it in a while, Mr. Altirra coder, might you fill in the blanks on the way one may adjust the palette?

 

anyway here is the thread that described palette swap in a few emulators

 

http://atariage.com/forums/topic/257966-adjusting-colours-in-altirra/?hl=%2Baltirra+%2Bpalette&do=findComment&comment=3610824

 

there are a few more here on AA

Edited November 6, 2017 by _The Doctor__

[phaeron]

Standard color calibration won't work here -- it can't (un)overlap hues or recover clamped colors as would be required here. Even if it did work it would horribly warp the rest of the desktop. Also, can't use it on the Atari side if that's the one you're trying to adjust.

 

Calibrating colors with a VBXE involved is going to be different than with standard GTIA because of the direct RGB output -- no matching hue steps or dealing with artifacting. First step is to figure out what you want the target to be: NTSC or PAL color scheme, emulator matching color or vice versa. Next step would then to be to make sure the two are using the same palette, uploading a palette to the VBXE or emulated VBXE as necessary. After that it's standard brightness/contrast/tint adjustment to try to match the two, looking at 256 color maps on both.

[leech]

Mind you, most of the color calibration has been through the GBS-8220. I was doing the color comparison between the S-Video output and the VBXE -> GBS-8220 on the same monitor. Ha, now that I think about it I wonder if the direct connection to my Dell 2001FP isn't working because I use a dual VGA switch box, since I believe the VBXE is supposed to output 15khz. But I think that's a different issue...