daveJ said:
SvennoJ said:
I checked their retina claim once and came to this: "The iPad 4 retina display needs to be viewed at a distance of 43.4" to make it a true retina display." At that distance you see it at 100cpd.
For comparison a 1080p 40" set needs to be viewed from 17ft4" away to see it at 100cpd. That's the upper limit and anti aliasing becomes irrelevant.
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like I said it depends on how good the vision of the person has, I assume the 17'4" is for imperfect 20/20 vision for 20/12 vision (common for teenagers) yuou need to be ~29 feet away
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I had to look up what 20/20 vision means to make the conversion. If I understand it correctly 20/20 vision corresponds to being able to read text where the black lines are seperated by 1 arc minute, which would indeed corresprond to 30 cycles per degree. (60 alternating black and white lines) So 100 cpd corresponds to 20/6 vision. Or instead of being able to read the Snellen chart from the standard 20 ft away, you would be reading the bottom line from 66.6 ft away.
I do not assume anyone can read the bottom line of the Snellen chart from 66.6 ft away. That's not how the upper limit of 100 cpd was determined. That was done by asking people to guess which pictures looks more 'real' by showing 2 pictures at different resolution next to each other. At around 100 cpd it became pure guesswork. Unfortunately it did not specifiy what the visual acuity was of the test group.
With the iPad 4 at 13" away from you, you should be able to read the smallest bitmap font if you have 20/20 vision. Someone with 20/12 vision should be able to read that from 21" away.
For a 40" 1080p tv, at 5ft2" you should be able to read the smallest bitmap font with 20/20 vision, 8ft8" for 20/12 vision. Maybe someone with 20/12 vision indeed needs to go all the way up to 166cpd at 29ft away to get an image completely free of aliasing effects. My eyes definitely aren't that good :)