OpenType has different ascender numbers?

[_martha_soule_]

We're converting our Mac Type 1 publications to OpenType and have noticed that the OpenType characters are ascending closer to the top of the text box in InDesign than the Type 1 characters did.
I checked into this with FontLab and noticed that for ITC Garamond book, the ascender height for the Type 1 fonts is 671, the descender is -218, the Caps height is 623 and the x height is 445.
For ITC Garamond Std Book, the ascender is 703, the descender is -297, the Cas height is 626 and the x height is 451.
These are substantially different numbers, resulting in reworking a large number of files to replicate the type 1 fonts.

Does anybody know the reason why this happened?
Looking forward to some enlightenment!

[Thomas Phinney]

I believe the OpenType version of ITC Garamond is based on the Type 1 MM version, not the plain Type 1 version.

Adobe does NOT make any promises of compatibility between Type 1 and OpenType versions of fonts, but we do document many of the kinds of things that they have changed. However, I don't think this particular issue is in there, and it should be. Sorry about that.

http://blogs.adobe.com/typblography/2005/12/type_1_to_opent.html

Regards,

T