Colour palette differences

[cools]

Anyone have a real idea why 80s JAMMA (and non JAMMA) games use a brighter colour palette to 90s games?

I've seen it thought that 80s = behind tinted glass, but I know from experience that the glass only makes a small difference to the palette.

I've also seen bits of information regarding the DC offset with AC coupled monitors, but this doesn't explain why there was a significant change in palette range around the turn of the decade. Did monitors suddenly change in their function?

Any ideas?

 

[trm]

Possible WAG coming up, could be easily shot down by anyone with more knowledge.

I think I've noticed (but it could be confirmation bias) that older games tended to use a resistor ladder to produce the RGB levels and often used 3 bits for red, 3 bits for green and 2 bits for blue to fit in their 8-bit byte data bus. So 7 shades of red and blue and only 3 shades of blue.

Newer stuff I've recently been looking at uses a 16 bit word as the move to 16-bit wide data busses for colour and it seems to be 5 bits per colour so you've got subtler colour steps and also transistors or custom silicon to produce the final analogue RGB. So 31 shades of each primary.

With 3 bits for red & green you don't have many brightness levels between 001 - dim and 111 - max brightness (even worse for blue, but retina biology comes in here too), so maybe it'd be a choice of 010 - pretty dim and maybe too dim on iffy monitors or 100 - bright on a decent screen and not too dim on a crappy CRT. A five bit range for RGB gives you double the colour steps.

I don't think the 0-0.75V P-P versus 0-5v P-P affects this though as almost everything I see seems to still be 0-5V, but I thought I'd mention it in case anyone knows better.

That's just made me think of the hardware which claim 16.7m representable colours which must be using 24 bit DACs.

 

[P-Man]

The 'behind tinted glass' is mainly due to CRT technology of the day, the Phosphor coating was quite a light grey on most CRT's until the development of darker phosphors into the mid-late 80's.

The tinted glass was a cheat to improve contrast and create actual blacks on the game screen if you weren't in a dingy, dark, light-devoid arcade. Remember that most early games were coloured objects moving around on a 'black' background. They weren't screen-filled with graphics because the hardware couldn't handle that, this left a lot of 'grey' background visible, where the intention was for it to be black.. hence, the tinted glass.