What are the differences are between "Optical" and "Metric" kerning in InDesign? In what cases would you use one more than the other - is there a hard rule to when you would select either? Or is it just personal preference? Any help is appreciated.
Personal preference really. Personally I always use optical. Some never do and prefer to do it themselves or use metric.
Optical kerning uses the form of the characters in the actual font and sets the kerning according to that for the best result. Metric kerning uses the built in kerning pairs in the actual font to set the kerning and where ther is none, you do it manually.
Or as the Help file explains it:
"Metrics kerning uses kern pairs, which are included with most fonts. Kern pairs contain information about the spacing of specific pairs of letters. Some of these are: LA, P., To, Tr, Ta, Tu, Te, Ty, Wa, WA, We, Wo, Ya, and Yo.
InDesign uses metrics kerning by default so that specific pairs are automatically kerned when you import or type text. To disable metrics kerning, select "0".
Optical kerning adjusts the spacing between adjacent characters based on their shapes. Some fonts include robust kern-pair specifications. However, when a font includes only minimal built-in kerning or none at all, or if you use two different typefaces or sizes in one or more words on a line, you may want to use the optical kerning option."
I believe that metrics kerning leads to faster text flow and redraw (Indesign doesn't have to do the analysis work itself), and probably for highly-designed fonts where overlaps are expected (like scripts with connecting strokes), metric may be more accurate IF the original designer created the font correctly. Kerning is an art, and optical kerning is, in a way, turning over that art to computer algorithms instead of leaving it to the font designer. Like any such endeavor, this can be better or worse depending on the care with which the particular font was created.
Also, metric kerning can't kern pairs in which one character in the pair is in a different font, italic or bold, or superscripted or subscripted. So if you've got a lot of text variables like P
a, you may be better off with optical.
Thanks for all the input! VERY HEPFUL! It seems that overall - personal preference is the main thing. I know this may be subjective - but for smaller font sizes (under 7pt) would you guys prefer to use optical or metric kerning? Just out of curiosity?
I always use metrics. I prefer to use kerns that the font designer has looked at rather than metrics generated by an algorithm. Given that it's usually agreed that the best kerning is achieved manually, I'm always quite amazed at the number of people who prefer app-generated kerns. (I've wondered whether this was not due in part to the name; if it was called "automatic" or "machine" instead of "optical" kerning and "metrics" was called ""manual" or "human" kerning, would we see a difference in the numbers?)
>Unless you're working with a font that is designed to be used at specific sized, optical is definitely better for small and large point sizes.
I don't see why. What does point size have to do with it - if a letter combnation is kerned properly using metrics at 12pt, why would it suddenly not be kerned properly at 6pt or 72pt? Yes, you should set the tracking tighter for display type and looser for small type, but this is an overall setting and I don't see how it makes a difference. (I prefer to set tracking in my styles.)
For 7pt type, I would ideally choose a font with optical masters and I'd still use metrics kerning.
I prefer optical even for text. On a good fast Mac, it really isn't slower. The built-in metrics of many fonts (even Adobe's!) are poor for many of the character pairs, especially numbers. Optical improves that.
Combined with good hyphenation and justifiction settings, optical gives you the most professional look, I think.
You do really need optical for big display type (where poor native character fit is more obvious) and for contiguous mixed fonts and sizes.
The exception is columns of numbers in tables. They align better if you use Metric or even None. ~A
>The built-in metrics of many fonts (even Adobe's!) are poor for many of the character pairs, especially numbers.
I haven't noticed such widespread problems. I would have thought that, if they were so poor, Adobe could just have used their kerning engine to kern their fonts. Can you give examples of these bad kerns?
>You do really need optical for big display type ... and for contiguous mixed fonts and sizes.
For really important display type and mixed fonts and the like, I do my own kerning.
I'd agree that "We'd" is too tight, but because I think the optical alternative is too loose and, because I haven't found a problem with other apostrophe kerns in Minion, I see this as an argument for a kerning editor, not optical tracking. In general, I find optical kerning sets Minion Pro regular too loose.
(I don't set French text, so I can't comment on that.)
Gill Sans is the worst. Especially bad with spaces before cap T and W. Try signing off World Vision on Weyerhauser Way in Federal Way, WA, with that!
We actually had a constantly updated kerning table for it at my old agency (you find a pair, you add it). When I moved to World Vision, where it was the corporate font, I couldn't believe they didn't use one. But they quickly moved to ID, and the (optically-kerned) rest is history.
>One thing to look forward to in CS4 is that GREP styles allows you to, in effect, set up custom kern pairs.
Ooh, cool. The CS4 upgrade calls to the geek in me. (Hello, medical references!)
I don't believe that's bad kerning as such; rather, it's what could truly be called "optical kerning", where the word space before letters such as W, T, and V is decreased to give an optically even look. You don't see it much in fonts these days (just as you don't see increased space before the heavier punctuation stops like colons, semicolons, etc), which is probably why it looks strange to many, but you can find reference to it in older typesetting manuals like Dowding's "Finer Points in the Spacing and Arrangement of Type".
The problem in Gill Sans is the combination of the kerning applied to the space-T (and space-W) and that applied to the period-space pair.
I suppose if InDesign were smart enough to deal with triplets, this wouldn't matter. But up until GREP styles, it hasn't been. Now, with GREP styles, if you're using Gill Sans, you can solve this problem by applying character styles to the triplets (or perhaps even just the space in the triplet) to overcome the this weakness in the Gill Sans built-in kerns.
Any default can be set by changing a value with nothing selected. With no object selected, change the kerning value in the Character panel. This will set the default for the document, but existing text and styles will not change. Change styles in the appropriate style panel, change any other text with Find/Change.
Do a bit more research. Generally speaking, optical should only be used for headlines, pull quotes, and larger type sizes. It does not work well on body copy. Do not make optical your default text setting without researching more fully. Optical kerning was created to fix bad kerning pairs which occurs less and less with digital fonts these days. Old bugaboos like an "A" next to a "T" resulting in a huge hole between the two have been amended with each generation and reissue of font faces. The use of optical kerning on headlines is because that's where a gap between letters and punctuation will be more pronounced and need correction to look good.
I will do more research, but from the first look, body text in Garamond 10 pt, 12 pt space leading, 2 paragraph columns looked better readable in Optics than in Metrics, which was a bit crowded for my impression. I don´t know if that might have a different impact in other font families, but i will read more and thanks again for the links to those articles.
You may want to look at your font settings and how to adjust letter spacing properly. Contrary to what Nini says, I believe it is bad practice to use optical kerning as a default value. If it were the best way to go, it would be the default setting for ID.
I think it was Michael Murphy who explained it at a recent NYCID users group meeting a few months back while showing how to automate production with style sheets and object styles. Anyone else there remember that? Bob? Sandee?
A major factor in NOT using optical kerning: It is a huge resource hog and will slow down screen redraw/production dramatically.
If optical kerning slows down my machine, I've never noticed. I think it is generally as least as good as metrics, often superior and definitely the way to go unless you want to slave over every kerning pair to get it just so.