the quest for correct vic20 lumas

[groepaz]

On Forum64 a Thread spawned about finding "the" proper vic20 palette. For a start, i knocked up a little test program that displays all the colors ordered by their (supposed) luminance (which is a very important property). You can find the test program here: https://sourceforge.net/p/vice-emu/code ... urtest.d64

It would be cool if some of you could do the following:

run the "luma test" program on your vic20. adjust your monitor for maximum contrast, but completely dial down the color saturation. if the display does NOT show the colors ordered by luminance ("brightness") then LIST the program, edit the DATA line at the bottom accordingly until it DOES show the right order - and post the result.

i tried to do this, but i am not entirely convinced. someone who has an s-video mod can probably do this better.

NTSC results would also be interesting

thanks!

[chysn]

This is a CR NTSC VIC-20 through a 1702 with Tint at detent, Color at minimum, Brightness at detent, Contrast at maximum.

I'm not really sure whether this shows the colors ordered by luminance or not... If I play with the monitor settings a bit, I can get all the colors to match their names. This is really a very well-preserved 1702.

The white looks nowhere near blue in real life. Probably scan-line or whatever happens to CRTs when photographed.

[Mike]

Jason, you're supposed to:

[...] completely dial down the color saturation. [...]

As long as the display shows colours, it is effectively impossible to bring them in order regarding their luminance.

The white looks nowhere near blue in real life. Probably scan-line or whatever happens to CRTs when photographed.

It happens quite often with screenshots of CRTs. The camera exposure is not synchronised with the frame scan and this easily leads to 'missing' parts (the exposure didn't see a full frame) or double exposure of parts of the screen, with times slightly longer than 1/60s.

[tokra]

Here we go, NTSC and PAL, both S-video-modded. I can't really decide how to order these, so I left the order as is.

NTSC:

PAL:

[groepaz]

I can't really decide how to order these, so I left the order as is.

Yeah, i had the same problem.... the first 5 are doable, the others are so similar its hard to tell. Your picture also shows the same annoying noise pattern in the chroma that i saw. :/

[Mike]

Judging from tokra's photos, I would swap Light Purple and Light Orange on both PAL and NTSC. Light Orange is ever so slightly brighter than Light Purple. The others are o.k. - but swapping these two would also be consistent with the order of Purple and Orange, i.e. the order within the normal versions of colours is the same as in the lighter versions.

[groepaz]

BTW - if you have svideo mod, did you actually *disconnect* the chroma input? that should remove the noise hopefully

[chysn]

Jason, you're supposed to:

[...] completely dial down the color saturation. [...]

As long as the display shows colours, it is effectively impossible to bring them in order regarding their luminance.

OK, I see the desired result after Tokra's post. As far as I know, there's no way to do that (colorless image) with the 1702, at least with the composite input.

[tokra]

BTW - if you have svideo mod, did you actually *disconnect* the chroma input? that should remove the noise hopefully

Oh, of course. Results look much better this way:

NTSC:

PAL:

[groepaz]

so, can you try to reorder them to make a better ramp? its really hard to tell on the picture :=) or does it all look fine?

[tokra]

It's not just the photo. The colors on a real screen are that close as well. I'd suggest moving Light Purple up two colors, below Light Red. This is similar to what Mike said, but I believe it is still darker then Cyan.

[groepaz]

well, try it and show us

[Mike]

By the way, my original Colour Test program prints the "GREEN" caption in black foreground colour, not white.

"PAL engine" and "NTSC engine" actually operate with timings that suit a MINIGRAFIK display window, and they have first been used to implement a software greyscale mode by mixing green/purple for a darker grey and light green/light purple for a lighter grey. At the time I was just too lazy to write yet another raster routine and repurposed these routines to produce the colour bars. In the 2019 re-release I posted a slightly improved version of both engines. They are now slightly more compact and avoid a side effect the table values of the auxiliary colour had on the background colour in the first visible hires pixel columns.

[tokra]

I fiddled around with the values a little, first on my LCD and also on my 1084. When I switched some values around because they looked darker/brighter, the new result suddenly looked the other way around. I changed all text-output to white so it wouldn't distract, but the strange results remained the same. Either way this seems to be the best order for both PAL and NTSC I could come up with. I know it looks like you should swap some colours in the middle but as said if I did that it suddenly looked worse.

NTSC:

PAL:

[groepaz]

can you please write out the order, i cant make out wth the last 2 or 3 are =) but the ramp looks good! (just light purple and light orange swapped around?)