# Re: Calculation Error

```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 Thursday, 8 June 2017 22:47:54 UTC