apca-introduction

commit

4f761ed3625fa9dc304c8d7f206869bc719442be

parent

a6a166dfe59a509db02cd24eb029f851d0199c4a

Author

Tobias Bengfort <tobias.bengfort@posteo.de>

Date

2022-08-04 04:14

spatial frequency: conclude that it should only be used to define thresholds

Diffstat

1 files changed, 7 insertions, 9 deletions

diff --git a/analysis.md b/analysis.md

@@ -286,21 +286,19 @@ angle.
  286   286 
  287   287 If content is easy to read because of its spacial frequency, I do not need as
  288   288 much color contrast. On the other hand, if the spatial frequency is bad, more
  289    -1 color contrast is needed. So we can define a minimum required color contrast
  290    -1 based on spatial frequency.
   -1   289 color contrast is needed.
   -1   290 
   -1   291 There is one caveat though: The spatial frequency only defines the contrast
   -1   292 threshold under which a pattern is not perceivable at all. Above that it has
   -1   293 barely any effect. So we the best way to use it is to define a minimum required
   -1   294 color contrast based on spatial frequency.
  291   295 
  292   296 Interestingly, a lower spatial frequency is not always easier to read though.
  293   297 [Studies have shown] that the optimal spatial frequency is at about 5-7 cycles
  294   298 per degree. Below that, features get slightly harder to detect. (Perhaps that
  295   299 is the reasons for the "you don't see the forest among the trees" phenomenon.)
  296   300 
  297    -1 There is one caveat though: The spatial frequency only defines the contrast
  298    -1 threshold under which a pattern is not perceivable at all. Above that it has
  299    -1 barely any effect. In the context of accessibility we should usually stay well
  300    -1 above that threshold. So it is not clear whether spatial frequency is a useful
  301    -1 concept in this context.
  302    -1 
  303    -1 On top of that, it is not obvious how to define spatial frequency for the web.
   -1   301 It is not obvious how to define spatial frequency in the context of the web.
  304   302 For text, font size and weight certainly play a role. But different fonts have
  305   303 wildly different interpretations of these values. Since fonts depend on user
  306   304 preference, we cannot know beforehand which fonts will be used. We also don't