I don't think there is only one way to do that task. You could use some tools in the Action submenu In Fontlab but that's not a perfect solution. What I do: I draw the first weight, for instance the light, when I'm satisfy of it I draw a bolder weight, black one for instance. After I interpolate those two the get the regular one. Do the same with the regular and the black one to get the bold weight. Even with the interpolation method, you still have to make some adjustment or retouch on all glyphs.

So far I drew the alternate weight manually on individual glyph. I use the lighter weight as a master and I enlarge horizontally and vertically nodes by nodes to be sure there are always in the same position. To make a better interpolation you have to have the same amount of nodes in each alternate glyph. I've already tried to expand individually, but this method seems doesn't fit to me. An other way I find pretty good an efficiency is to work with the “Interpolate nodes” under the Contour menu. You start from a lighter or bolder weight and move the nodes at the distance you want and it keep on background the original as long you work on.
Hope this will be helpful.

Making a thing of value always takes hard work. While there are tools to help you find a starting point for between states (interpolation), even these must be visually corrected and adjusted to their new role. Drawing the extremes requires the most work but does not assure a smooth transition during interpolation. Relax and enjoy the drawing part, it is the most rewarding and least time consuming phase anyway.

So what about italics? Do you use the same process? Do you edit the initial glyphs or draw new ones (besides letters that usually look entirely different in italic like 'a')?

There’s a good explanation of the process for converting romans to obliques to italics in the how-to section of the typowiki. Some characters have to be completely drawn, especially in serif fonts. Some people use interpolation programs (Remix Tools, UFO Stretch) to manipulate the curves rather than just slanting.

There are worse things possible than leaning towards the left :-)

Is there an italic typeface that leans to the left (latin-based alphabet) that you (anybody) would consider using for design work — (and what kind of possible uses/scenarios could such a face have)?

Mr. Wikipedia provided some odd examples / uses (German maps?):

"Left-leaning italics

"In certain Arabic fonts (eg: Adobe Arabic, Boutros Ads), the italic font has the top of the letter leaning to the left, instead of leaning to the right. Some font families, such as Venus, Roemisch, Topografische Zahlentafel, include left leaning fonts and letters designed for German cartographic map production, even though they do not support Arabic characters.

"Upright italics

Fonts such as Jan van Krimpen’s Romanée, Eric Gill’s Joanna and Martin Majoor’s FF Seria have italic fonts that only have cursive designs, but not the leans typically associated with italic types."

Venus as an example? Really? The other example, Roemish, looks startlingly smooshed/underdeveloped in the italic too...(and then I came across the startling phrase: "upright italics" —is that a legit term I've overlooked until now?)

Martin,

Superpolator is €250, not 'incredibly expensive'. It literally pays for itself in a week.
That said, Superpolator does not make interpolation possible, just easy.

If you have the incredibly expensive software FontLab Studio, you have a Python API for that. Install the incredibly free RoboFab and start writing your own interpolation code. It's actually rather easy:

from robofab.world import NewFont
f1 = your one font
f2 = your other font
x = interpolation percentage
interpolationfactor = float(x) / 100
f3 = NewFont()
for n in range (0, len(f1)):
-- c = f1[n].name
-- g = f3.newGlyph(c)
-- g.interpolate(interpolFactor, f1[c], f2[c])
-- f3[c].mark = f1[c].mark
-- g.update()
-- bar.tick()
f3.update()
print "whee, free new font!"

Replace "-- " with a tab.(What, no indentation? No syntax colouring?)

The Robofab website has a bunch of reference about Python programming, the RoboFab libraries, "glyph math" and interpolation.

Hope this helps,
Kai

I just realized Superpolator is not for Windows. Could you recommend (almost) equally good software for Windows? Otherwise I will look into the RoboFab manual scripting, but I naturally prefer to do it without codes. Thanks a lot for the help, by the way. I really appreciate it.

I generally start with Regular.
Then I make an Extra Bold by adding as much weight as I can with the "change weight" feature, without it looking too weird, and then manually adding more weight by a combination of nudging stems and dragging points and vectors.
At the other end of the spectrum, I make a Hairline weight by drawing a path and adding a stroke value.
Then I interpolate between these three "weight nodes" to create the other weights.
It's important to develop the metric parameters of all three base weights at the same time, especially the alignment zones, because it's likely that you will want to have the alignment zones the same for all weights.

David, what did you want to express? Approval or disagreement? If the latter, why?

The interpolate function in FontForge works just fine with values <0 or >100, but errors resulting from unperceived dissimilarities in the base designs then become even more exaggerated. It also has a set of style options including changing weight, x-height, to extend or condense, separate functions for making italics and obliques, and some other toys I still haven't played with.

"inconsistencies in interpolated/extrapolated stem widths due to rounding."

I am surprised that such things are not corrected after the interpolation is output. I know I spend hours doing it and assume it to be a normal industry practice to make corrections. Also, my choice of which "number" to choose as a tweener weight is partly governed by checking stem fluctuations due to rounding. I might pick 647 instead of 650 if the stems were more consistent with that number--I still do a cleanup, though.

It would drive me nuts not to correct it.

@nickshinn wrote: because it's likely that you will want to have the alignment zones the same for all weights.

Huh. I think there is some difference of opinion on this point. Or maybe I misunderstand you? If you mean, the amount of overshoot is likely to be consistent, that may be. But if you mean, the x-height, cap height and descender depth are likely to be the same, at least some designers disagree. For a heavier weight, one might compensate with either a greater x-height (my preferred solution, one I've seen from a number of type designers whose work I appreciate), or a smaller cap height (the approach preferred by Robert Slimbach, another type designer I respect a great deal). Or one could do a smidge of both, I suppose.

Regards,

T