Optical Kerning

Optical Kerning adjusts the spacing between adjacent characters based on their shapes and pays no mind to the kerning pairs.

Theoretically, Optical kerning will give you more consistent character spacing, because every character pair, even the most unlikely ones like zh or xw or gk, is kerned based on its character shapes. It's a matter of preference, but here are some things to consider:

• If your font includes few built-in kerning pairs, you're better off with Optical Kerning. Decorative and novelty fonts are likely to have few kerning pairs.
• When combining two typefaces in the same paragraph, the two fonts may use very different kerning metrics and may not look right side by side. This is another occasion when you'll be better served by Optical Kerning.
• You might want to view Metrics vs. Optical Kerning as a microcosm of the timeless drama of man vs. machine. Optical Kerning will be more consistent, more mathematically correctbut will it look better? Ultimately it depends on the quality of the metrics you are comparing it against.

Figure 5.3. Comparison of Metrics kerning (example A) and Optical kerning (example B) using Times. The amount of difference will vary from font to font.

Figure 5.4. Metrics Kerning (example A) vs. Optical Kerning (example B) when using mixed fonts.

Figure 5.5. Metrics Kerning (example A) fares better than Optical Kerning (example B) when using script faces.