Supersized em square

Nick Shinn

I came across this magnificent specimen recently—Sharp Type’s Carta Nueva by My-Lan Thuong, 4096 units to the em—and wondered which other typefaces have ventured into such expansive territory. 

Piotr Grochowski

The em is a fundamental scale so this actually means the unit is ¹/₄₀₉₆ em.

Hrant Հրանդ Փափազեան Papazian

Yet another place capitalization matters...  :-)
an em: the unit.
the Em: the number of units composing the height.
(Although usage certainly varies.)

Chris Lozos

I use 4000 for hairline fonts

Nick Shinn

The linked AIGA article described it thus: “4096 units per em scale”.
I spose I should have written “4096 units to the em-square”?

But anyway—other “big em-square” fonts?

Thomas Phinney

Piotr Grochowski said:

The em is a fundamental scale so this actually means the unit is ¹/₄₀₉₆ em.

u = 1/4096 * m
  is mathematically synonymous with
u = m/4096
  and
4096 * u = m

Piotr Grochowski

Thomas Phinney said:

Piotr Grochowski said:

The em is a fundamental scale so this actually means the unit is ¹/₄₀₉₆ em.

u = 1/4096 * m
  is mathematically synonymous with
u = m/4096
  and
4096 * u = m

But the em remains constant given the same point size. So this is outline definition precision.

Erwin Denissen

Nick Shinn said:

The linked AIGA article described it thus: “4096 units per em scale”.
I spose I should have written “4096 units to the em-square”?

But anyway—other “big em-square” fonts?

Gimlet X-Ray has 5000 units per em.

Igor Petrovic

What is the main disadvantage of high UPM (let's say above 2000)? I guess font size, but maybe some other things like compatibility with some text processing apps, problems on the web, etc.? 

Jens Kutilek

If you have a large upm setting and very wide glyphs, it may cause the coordinates to break some systems.

E.g. if a glyph is 3 em wide, and has a point at x = 12000, and the rasterizer uses an oversampling factor of 5 in x-direction, the coordinate will land at 60000. If the rasterizer should happen to use signed short integer values for calculations, only numbers between -32,768 and 32,767 can be handled. Of course, rasterizers usually don't use the unscaled coordinates, but will scale them to 1/64th pixel first.

But I think I remember that e.g. Windows could not display a very wide glyph with ClearType. That may be a thing of the past now.

Georg Seifert

Above 4000 unites you get in trouble with Adobe apps. I through that was fixed but were had a case on the forum just recently.