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Thread: Snellen Chart
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Old 22nd November 2004 | 10:42
  #5 (permalink)  
slim_slag
 
Joined: Jan 2001
Posts: 1,981
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From: He's on the limb to nowhere
G_STRING,

Fair enough.

Slim_slag now slinks off and mutters about the youth of today wanting to be spoon fed everything and having no initiative or desire to actually understand the principles behind things anymore. Good job there are computers on flight decks, huh?

For those who might be interested, this is O-level physics stuff. It's not the size of the letters that matters on it's own, but the size together with the distance.

So, in a Snellen chart you change the size but not the distance. With a tape measure and a supermarket car park you can use the known height of the letters on a car number plate, but change the distance you stand from them to get the desired visual acuity numbers.

So one question G_STRING? What has the sequence of letters got to do with it? How do you think they measure the visual acuity of people who cannot read?

Cheers.
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