In Leopard (10.5), a pop-up menu provided a number of options for font smoothing—automatic, standard, light, medium (“best for LCD”), and strong.

In Snow Leopard (10.6), though, that’s been simplified down to simply a yes or no option: “Use LCD font smoothing when available.”

In practice, however, that’s not the case. The problematic LCD displays could be  Dell, Samsung, LG, HP, EIZO, Lenovo.

The problem was that the text on the Dell was really “light” and hard to read after upgrading to Snow Leopard (10.6). This made it tougher to read, and led to eyestrain if you are using  the machine for an extended period of time.

Lest you think this issue is restricted to those running homebrew netbook Macs, however, that’s not true—apparently standalone LCD displays by Dell, Samsung, LG, HP, EIZO, Lenovo, and possibly others are affected as well.

The top portion of the image is how the document appeared prior to applying the fix;
The bottom was taken after the fix.

Notice how the top image is quite light—dots on “i” characters are hard to see, and the text has an overall gray tinge to it. In the bottom image, the gray is gone, and everything is a bit bolder while still being clear and crisp.

Before (top) and after (bottom) the fix

By zooming in a bit, it’s easy to see the difference between the before and after images.

The top portion of the image at right is before the fix; notice that the font smoothing is done completely with levels of gray.

In the bottom portion of the image, taken after the fix, you can see not only more levels of gray, but the subtle use of some colored pixels to smooth the font—there’s a yellow pixel on the left edge of the dot on the “i,” for example.

If you’ve got an LCD panel that you think looks worse than it did before upgrading to 10.6, you can try this fix to see if it makes things better.
How? Just open Terminal (in Applications -> Utilities) and paste this command, then press Return:

defaults -currentHost write -globalDomain AppleFontSmoothing -int 2

The 2 at the end is equivalent to the old “Medium – Best for flat panel” setting in 10.5. You can also use 1 for light smoothing, and 3 for strong smoothing. This change will only affect newly-opened applications — anything already running will have to be restarted to see the affect of the changes.

Note that if you go back into the Appearance panel and toggle the font smoothing setting, you will override your manually-set value—so don’t do that if you value your newly-smoothed fonts.

Howto better font smoothing on some LCD displays is a post from: My MacOS X