Previous Message
Next Message

Re: [css-d] understanding scaling factors for % and EM

Sent by John A. Lewis on 30 September 2002 05:05


Hello Timothy,
Sunday, September 29, 2002, 9:27:19 PM, you wrote:

> Does any of this sound logical?

A quick check shows your numbers to be right.

> I seem to recall someone (Eric?) awhile back saying that EM is not
> exactly %, i.e. .8em ~= 80%

I'm sure em and % have differences; I just don't know what they are.

> I'm trying to put this into practice at
> http://tntluoma.com/css/tests/font-sizes.html

The CSS2.1 draft changes the scaling value from a static number
(originally 1.5 in CSS1 and revised to 1.2 in CSS2) to a variable
scale. Says CSS2.1:
<http://www.w3.org/TR/CSS21/fonts.html#font-size-props>

  Note 2. In CSS1, the suggested scaling factor between adjacent
  indexes was 1.5, which user experience proved to be too large. In
  CSS2, the suggested scaling factor for computer screen between
  adjacent indexes was 1.2, which still created issues for the small
  sizes. The new scaling factor varies between each index to provide
  better readability.

Here are the values converted to decimals:

xx-small: 3/5 = 0.6
 x-small: 3/4 = 0.75
   small: 8/9 = 0.888...
  medium: 1   = 1.0
   large: 6/5 = 1.2
 x-large: 3/2 = 1.5
xx-large: 2/1 = 2.0

This works much better than the previous systems.

-- 
John
Previous Message
Next Message

Message thread: