- From: Wayne Dick <wayneedick@gmail.com>
- Date: Thu, 8 Jun 2017 15:46:11 -0700
- To: public-low-vision-a11y-tf <public-low-vision-a11y-tf@w3.org>
- Message-ID: <CAJeQ8SCtphBZ61PrOv-KA1UXxYBzr-tDijch5oTyPBKGvMyRFQ@mail.gmail.com>
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 > > > > > > > > > > > >
Received on Thursday, 8 June 2017 22:47:54 UTC