Re: IIgs RGB to YPbPr Component experiment

[Roger Johnstone <news2006@roger.geek.nz>]

In <1151032188.304361.126770@i40g2000cwc.googlegroups.com> David Wilson 
wrote:
>> I don't think this is the problem, because other screens look fine.
>> It's just those Super screens with color that are funny.  I might 
>> need to post more pictures to make the effects better understood.
> 
> I would suspect it is because the Super screens are using dithering to
> increase the number of available colors. From the Apple_IIgs wikipedia
> entry:
> 
> "640=D7200 pixels with 16 dithered colors. In this mode, two palettes 
> of four pure colors each are used in alternating columns. The hardware
> then dithers the colors of adjacent pixels to create 16 total colors 
> on the screen. This mode is generally used for programs requiring 
> finer detail such as word processors and the Finder."
>
> It looks like the sampling rate and pixel spacing of the LCD is 
> messing up the dithering that resulted when the analog RGB Apple Color 
> monitor was used.

I think you're right. Black and white is not dithered and looks fine in 
the picture. The Apple menu icon also looks fine, but the menu bar scan 
lines use the non-dithered 4-colour mode, and have their own palettes so 
that the Apple icon can be drawn in the right colours.

-- 
* Roger Johnstone, Invercargill, New Zealand -> http://roger.geek.nz
* PS/2 Mouse Adapter for vintage Apple II or Mac
* SCART RGB cable for Apple IIGS