Why does my extended desktop setup cause ghosting on my monitor?

Q I have a Dell 21in monitor that has been calibrated with a SpyderPRO and works fine with a crisp image.

I recently bought a Sony Vaio VGN-FW21Z laptop, mainly to take the strain off my aging P4 machine when running Adobe CS3 and other multimedia software.

I've connected this to my monitor, keyboard and mouse via a Starview SV231USB KVM switch, so I can use both computers at the same time.

I've got the Sony’s built-in display running at 1920x1080 and the Dell 21in monitor set up as an extended desktop, at 1600x1200.

Unfortunately, with this configuration, text on the Dell monitor suffers from horizontal ghosting, with a faint shadow to the right of each letter.

Connections to both computers are via VGA D-Sub cables.
Barrie Potter

A The problem here is almost certainly the KVM, as many struggle to support very high resolutions without ghosting.

You have a number of options open to you. First you could try simply running the extended desktop at a lower resolution – most KVMs should handle 1024x768 without ghosting.

A better solution is to avoid the KVM altogether for the video signal and instead connect your laptop and desktop directly to the Dell monitor.

We’re not sure which model you have, but many monitors have multiple inputs. You’d then continue to use the KVM to share the keyboard and mouse, but use a button on the monitor to switch the display input.

It’s also worth noting that analogue VGA begins to suffer at very high resolutions, with high-quality cabling and short lengths required to avoid ghosting at 1600x1200 or higher.

If possible, use DVI connections between your computers and monitor for the crispest, ghost-free image.

Your Sony laptop has an HDMI port, which should be convertable to DVI with a simple adapter or an HDMI to DVI cable.

Do check with Sony first though, in case the HDMI port is limited to delivering certain HD resolutions only, like 1280x720 or 1920x1080.