[net.micro.cbm] C64 Ghosts and Audio Input

hdw@mhtsa.UUCP (08/11/83)

	I have two questions regarding the C64:

1)	I have noticed that when I use certain color combinations
(character and background), I get a ghost of the character immediately
afterwards.  This occurs even with color combinations that are supposed
to be good according to the color combination chart in the PROGRAMMERS'
REFERENCE GUIDE.  An example is using red characters (color code 2) on
a white background (color code 1).  I am using a video monitor.

	Does anyone know if this is the infamous "video sparkle" effect,
a defect in my C64, my monitor, or if it is just something I have to live
with?

2)	In the process on connecting my C64 to a monitor, I noticed that
one of the leads on the audio/video DIN plug is labeled as "audio input".
Checking the schematic in the PROGRAMMERS' REFERENCE GUIDE (Is there
anyone out there actually attempting to use a C64 without the aid
of this document?) I determined that this line is an input to the SID
(synthesizer) labeled "external input".  According to the SID data sheet,
this input is mixed with the output.  Has anyone had any experience
using this feature?  Is it useful?

			Harlan Worchel
			Bell Labs - Murray Hill, N.J.
			mhtsa!hdw  7E-306  582-5411

kurt@fluke.UUCP (Kurt Guntheroth) (08/12/83)

There is a problem that occurs when you change from one color to another
using inexpensive video hardware and inexpensive video generating 
hardware.  A hardware person explained it to me at one time and even gave
a name for the problem, but I have forgotten all that.

Basically, some colors, or more particularly, the transitions between some
colors and other colors causes smearing.  It is a linearity problem in
video amplifiers and color video generating circuits and cannot be cured
easily without spending a lot of money.

I have a color monitor and I get smearing.  You can reduce the smearing by
getting a better monitor but it wont go away altogether.  On the commodore
64 and the commodore monitor, you can decrease the smearing by connecting
the luminance output.  (The cable that comes with the commodore monitor does
not have a luminance connection, they want you to pay $25 extra to get it.
Disgusting) I bet you don't have ghosts when you use red over black.

Anyway, this is not the 'sparkle' problem.  The sparkle problem looks like
your TV set looks when you turn on a vacuum cleaner or blow drier nearby.
Strange snow in the picture.