Type 1 to OpenType font conversion FAQ
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This document is aimed at users who are migrating from Type 1 ("PostScript") fonts supplied by Adobe to the equivalent OpenType fonts. It addresses common questions users may still have even after reading the OpenType User Guide and readme file (both available at http://www.adobe.com/type/opentype)
There were many changes during the Type 1 era, then there were changes made in converting to OpenType (see also below). Keep in mind that the OpenType fonts in the Adobe Type Library have the last Type 1 versions as their starting point. So if you are trying to tell how OpenType fonts will differ from their Type 1 counterparts, you may want to read both sections in case your Type 1 versions were not the latest revisions.
Adobe makes no promises of compatibility between the old Type 1 fonts and the new OpenType fonts. That being said, most of Adobe's OpenType fonts started with the same outlines, widths and kerning as their Type 1 counterparts. The likelihood of reflow when replacing Type 1 fonts with OpenType equivalents depends on which fonts you are using, which characters you are using within those fonts, and what applications you are using them in. Read the "changes made in converting the Adobe Type Library to OpenType" and the "summary of behavior changes and reflow issues" below to understand more.
Which Adobe Type 1 fonts match which OpenType fonts?
There are tables available at http://www.adobe.com/type/opentype, linked on the right side of the page. One table covers only multiple master Type 1 fonts, and the other covers all other Type 1 fonts.
What changed during the Type 1 era?
1) ITC Eras and Optima got significant revisions around 1993; the Type 1 versions from 1989-93 are not compatible with current software and operating systems.
2) Other than that, even the earliest PostScript Type 1 fonts should be fine as far as Adobe is aware. In fact, there are a few fonts in the Adobe Type Library that were never updated in their Type 1 form after their initial release in the 1980s.
With regards to designs and metrics, few Type 1 fonts had significant changes until the switch to OpenType. Prior to that, the major changes were:
3) Courier went through several major versions, with significant design changes in the outlines and stroke endings. Times and Helvetica also underwent major design revisions in the early 90s.
4) For the fonts bundled with PostScript 3 output devices, there were a number of revisions, which include many common fonts. Where not all accented characters were kerned, those fonts had their kerning extended to add more kerning for accented characters. Additionally, all these fonts, plus any other fonts in the same retail packages, had the euro character added. Note that both of these changes were made to all Adobe alphabetic fonts as part of OpenType conversion, later on. Here is a list of the families/packages that had this change made while they were still in Type 1 format.
Albertus MT
Antique Olive
Bodoni (packages Bodoni 1 & 2)
Cooper Black
Gill Sans (packages Gill Sans 1 & 2)
Goudy (packages Goudy 1 & 2)
Helvetica Condensed
Helvetica Narrow (but this family was not converted, see above)
ITC Avant Garde Gothic
ITC Bookman
ITC Lubalin Graph
ITC Mona Lisa
ITC Zapf Chancery
ITC Zapf Dingbats
Joanna MT
Letter Gothic
New Century Schoolbook
Stempel Garamond
Univers (packages Univers 1 & 2)
Univers Condensed
What changes were made in the OpenType conversion?
With the switch to OpenType, Adobe made many more changes to the Adobe Type Library besides the ones already mentioned during the Type 1 era.
1) Helvetica Narrow was not converted to OpenType. Why not? This font family was developed for use in printers when ROM space was very scarce, so it was created by mathematically squashing Helvetica by 18% (to 82% of the original width), a painful compromise which resulted in distorted letterforms and thin vertical strokes next to thicker horizontals.
For general use, Adobe recommends Helvetica Condensed instead, which was actually designed to be condensed, so that stroke widths are unchanged. If an exact match to Helvetica Narrow is needed, many programs, including Microsoft Word, InDesign and Illustrator, allow the user to horizontally scale a font to any desired percentage. One could use Helvetica LT Std and apply an 82% horizontal scale factor.
2) all or almost all of Robert Slimbach's typefaces had revisions made to them. In most cases this meant re-spacing and re-kerning. In some cases there were significant design changes. The largest changes are noted here, along with a list of all the Slimbach typefaces which received any tweaks at all. Note that Slimbach's two designs for ITC did not get these sorts of modifications (ITC Slimbach and ITC Giovanni).
3) The biggest single change is the italic for Cronos Pro, which is very different from the old version (less cursive).
4) Minion Pro has been reworked from the previous Minion MM, though these differences are very subtle, they also include slight changes to the selection of instances; text changed from Type 1 Minion to Minion Pro will very likely reflow slightly.
5) Utopia Standard had optical size variants added, and the "regular" design is not quite the same.
6) The full list of families affected by noticeable changes in design or spacing are as follows:
Adobe Garamond
Adobe Jenson
Caflisch Script
MinionMyriadPoeticaSanvitoUtopia
7) Some other Adobe Originals had significant additions or modifications. In particular, Lithos Pro and Trajan Pro got real small caps to accompany their all-cap designs. Text entered in lower case will turn into these small caps if one switches from the Type 1 fonts to the OpenType versions. Text entered specifically as caps will remain the same.
All fonts with "Pro" in their names had additional language support added. This will not cause issues moving from the old version to the new one, but of course if one takes text set using language support not present in the old fonts, and sets it in the old font, depending on the application being used, that text will either be missing (show notdefs) or fall back to some other font.
8) all alphabetic fonts had a euro added, if they didn't already have one (affected most fonts).
9) all alphabetic fonts had another 16 characters added, namely the 14 Mac "symbol substitution" characters, the litre and estimated symbols. "Symbol substitution" describes a Mac-specific scheme whereby if a certain character was typed in a Type 1 font with StandardEncoding, both ATM and the printer driver would get a generic glyph in the Times style from the Symbol font (it wasn't actually present in the original Type 1 font). In OpenType, instead of substituting a generic glyph from Symbol, the system infrastructure relies on a glyph being actually built into the font. Adobe's OpenType fonts all have font-specific versions of the former Symbol substitution glyphs, which have different widths than the glyphs from Symbol. The affected characters are as follows: partialdiff, Delta (math), integral, pi (math), product (capital math pi), root, infinity, lozenge (diamond), summation (cap math Sigma), approxequal, ohm (capital math Omega), lessequal, greaterequal.
10) all fonts that had accented characters which were unkerned had their kerning extended to deal with accented characters.
11) if a typeface had supplemental fonts such as "expert sets," swashes, or separate Cyrillic fonts, these were merged with the base fonts. The presence of such supplemental fonts can change behavior in typographically savvy apps, which will make use of more ligatures, or real small caps (instead of faking them). In such cases, several Type 1 fonts may equal a single OpenType font.
12) Multiple master fonts were spun out into individual fonts for each former "instance" of the MM. In such cases, you have one MM font that equals a whole set of OpenType fonts.
13) In cases where the original font was multiple master, and had additonal multiple master supplemental fonts, there is a complex many-to-many relationship between the original fonts and the OpenType fonts. Essentially, you have a set of fonts going in, and a set coming out, but they are divided up in an entirely different way.
Summary of behavior changes and reflow issues
If all the following factors hold true, then you are unlikely to get significant reflow in moving from Adobe Type 1 fonts to their OpenType counterparts, though there are no guarantees of 100% compatibility. (See above section for details on the reasons behind items 1 through 5.)
you're using Adobe fonts, but not Adobe Originals
setting text in English
you're using non-accented characters
you're using only characters that were present in the previous fonts, and not using the former Symbol substitution characters
you're using applications (such as virtually all professional graphics applications) that base line spacing solely on point size or leading, and don't use the bounding box of the font to determine standard line spacing
If you are using advanced applications that support OpenType layout features, the existence of the added typographic glyphs may contribute to changes in what is displayed. For example, the OpenType version of a font may have more "standard ligatures" than the Type 1 version. Since these ligatures are on by default in savvy applications, this can create differences (though the OpenType version will be better, typographically speaking).
Similarly, there can be changes in the behavior of small caps between the Type 1 and OpenType versions of the font. With a Type 1 font, one had to switch to another font to get real small caps. If one simply used formatting in the application, the result would be 'faux' (fake) small caps, created by scaling the capitals. Faux small caps have stroke weights that are lighter than the rest of the font, and may be narrower in width. If one switches to an OpenType version of the same font, and it has real small caps merged into the font, and the application knows how to use them when they're available, the faux small caps will be switched for real ones. This is typographically preferable, but will likely result in wider text and possibly cause reflow.
Using office-level applications, reflow due to line spacing differences is more likely, thanks to item C5 above. The difference is because such applications typically use the font's bounding box to determine default line spacing. The added characters in the OpenType fonts can change the bounding box, especially in cases where the OpenType fonts merged what were formerly supplemental fonts in Type 1. The presence of swashes and/or ornaments in the OpenType font often accounts for the most serious line-spacing changes in office-level applications. NOTE: In applications where this is a problem, it can be reduced by setting the text using a specific point-based line spacing rather than the usual "single spacing" or "double spacing" kinds of options. If you can set the line spacing to a point-based value that is equal to the default line spacing, you should be able to preserve that line spacing when later switching to an OpenType font.
OpenType ReadMe
OpenType FAQ
OpenType FAQ (Japanese)
OpenType Developer Information
Multiple Master to OpenType cross reference
Type 1 to OpenType Conversion FAQ
Type 1 to OpenType Cross Reference
Pi Font Info
Microsoft Typography
Required Utilities
AdobePS printer drivers (Mac)
AdobePS printer drivers (Win)
StuffIt Expander
OpenType articles
OpenType ushers in new era of typography