# Re: Calculation Error

```I agree Alastair. There are two salient facts. 1) Letter and word spacing
is only effective over a small range. 2) The overall impact space required
is determined by the average space taken for each letter. Combining these
we could give a bounding function like this: Total expansion of text <=
(1+letterSpacing)*(1+(1/5)wordSpacing)*(charSpace /
averageCharacterSpace)<= .15.

Where we supply a function to calculate charSpace and a table of
averageCharacterSpace.
charSpace= the average space taken by a character in the font family for
substitution
averageCharacterSpace = The average charSpace taken over an agreed set of
fonts families in script for a given language. The unicode ranges for each
language are set for now by Unicode 9 (like Latin (32-127), Arabic
(0600-06FF), CJK (4E00-9FFF) etc.

Wayne

On Fri, Jun 9, 2017 at 2:39 AM, Alastair Campbell <acampbell@nomensa.com>
wrote:

> Ah, that’s great, we can get a useful result without as big an impact as I
> thought it might be.
>
>
>
> I suggest two actions:
>
> 1.  We try to come to one measure for horizontal space increase.
>
> 2.  We use Wayne’s calculations (or a summary of) in the understanding
> doc to show the justification.
>
>
>
> Wayne, we’re looking to come up with a total increase from possible letter
> space, font-family substitution and word spacing.
>
>
>
> So if letter spacing is 0.045em, and word spacing is 0.16em, that makes a
> roughly 15% increase in width on my test sentence:
>
> https://alastairc.ac/tests/word-spacing.html (at the bottom).
>
>
>
> If we used a letter-spacing only of 0.065em, that comes out at the same
> size horizontally. (Note tiny differences in letter-spacing make a big
> difference, word-spacing not so much.)
>
>
>
> Would that letter-spacing value suffice?
>
>
>
> Cheers,
>
>
>
> -Alastair
>
>
>
>
>
> *From: *Wayne Dick
>
>
>
> Just in  case I made some more errors, here is my code.
>
> http://nosetothepage.org/fontApps/src/HTML/
> http://nosetothepage.org/fontApps/src/js/
>
> The relevant files are:
>
> For indivudula font family at a time
>
> fontWidth.html
>
> fontWidthX.js
>
> famStatt.HTML
>
> famStats.js
>
> famWidth.js
>
>
>
>
>
> Wayne
>
>
>
>
>
> On Thu, Jun 8, 2017 at 3:46 PM, Wayne Dick <wayneedick@gmail.com> wrote:
>
> The empirical test I left off: I used my sample string unicode 32-126 and
> inserted  spaces every five characters. Then I set the letter spacing to
> 0.045 and word spacing to 0.16. Then I ran the test on Tahoma. I got that
> the average space taken by each character was 9.24px. Without the spaces
> and with normal spacing I got an average of 8.6px. 9.20/8.6=1.074. Pretty
> close to the theoretical estimate.
>
>
>
> On Thu, Jun 8, 2017 at 3:10 PM, Wayne Dick <wayneedick@gmail.com> wrote:
>
> When Alastair did his computations and got 150% enlargement that set off a
> red flag for me. I double checked Alastair's computations and he is right.
>
> Letter spacing should change to 0.045em NOT 0.12em.
>
>
> My mistake was in using the research percentages applied to whole letters,
> not the space between them as the researcher MacLiesh suggested. Thus, our
> letter spacing should be applied to the spacing between letters, not to
> letters. That is 0.12x0.25=.03em.  There was actually an improvement up to
> 0.24 of the space between letters. Then the improvement flattened. I did a
> linear interpolation from 0 to 0.24 when I got 0.12. I think in this case
> the research max 0.06em could make size problems for developers, but the
> min 0.03em is a little small from my personal experience, and the research
> plots in the MacLeish research. Thus, I recommend linear interpolation
> again to get 0.045em.
>
> Word spacing is correct because it is applied to 1em, (a space character
> approximately). However when we compute the size increase due to word
> spacing we must divide by the average word size (language dependent (about
> 5 in English usage)).  So, to compute the effect of letter spacing on text
> length we should apply the following multiplication factor:
>
> (1+letter-spacing)(1+(1/5)word-spacing)<= (1+0.045)(1+0.32)=1.07844<1.08.
>
> Empirical Evidence: Let us look at an average font like Tahoma. The
> average character width is 8.69px including normal letter spacing.
>
>
>
> Conclusion:
>
> Word spacing should not change. Letter spacing should change from 0.12em
> to 0.045em.
>
> Wayne
>
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>
```

Received on Friday, 9 June 2017 17:00:04 UTC