Quote:
Originally Posted by
nickbuol
Amazing how people are fascinated by new tech, even if
the human eye can't tell the difference. Like people that sit in their living rooms, 15 feet from a 42" flat panel that they bought 4 years ago. They HAD to have 1080p because that was the "best", but what the marketing and sales guy didn't tell them is that their eyes won't be able to tell the difference in 720p and 1080p in their situation, and yet a LOT of sub 50" 1080p sets were sold.
That's a common myth. The people in your example would benefit from 1080p, and actually even 4k (2160p) to some extent if their eyesight is very good.
The theoretical limit of the human eye is ~0.2 amin (arcminutes) per pixel (or ~0.4 amin per cycle):
Quote:
More recent work on photoreceptor density and spatial resolution has shown that the receptor array in the human visual system can resolve in the order of 6/1 (20/3) or ~150 cycles/degree (Curcio et al, 1990; Miller et al., 1996; Roorda and Williams, 1999).
http://webvision.med.utah.edu/book/part-viii-gabac-receptors/visual-acuity/
In practice, NASA spectroscopist and researcher
Dr. Roger N. Clark (who ought to know a thing or two about optics) has summarized the relevant research and found the limit to be about ~0.3 amin per pixel (or ~0.6 amin per cycle or line pair):
Quote:
The acuity of 1.7 corresponds to 0.59 arc minute PER LINE PAIR. I can find no other research that contradicts this in any way.
Thus, one needs two pixels per line pair, and that means pixel spacing of 0.3 arc-minute!
http://www.clarkvision.com/articles/eye-resolution.html
So, what does this mean? It means that if we know any two of the following variables: screen size, viewing distance, and resolution, we can calculate what the third should be for us to approach "perfection".
In my formulae (intended for Google), the variables are:
x = screen size in inches ("in") on the diagonal (for a 16:9 screen)
y = viewing distance in feet ("ft"), can be changed to metres ("m")
z = vertical resolution (screen height in pixels)
The constant 0.3 arcminutes is the target pixel pitch (and can be lowered further by "videophiles" who desire an additional safety margin, or raised if you know your eyesight isn't very good).
To calculate from what viewing distance (or longer), vertical resolution z on screen size x approaches "perfection":
Code:
( (x in) / z * 9 / ((16^2+9^2)^0.5) / tan( 0.3 arcminutes ) ) in feet
Example: Full HD (1080p) on 42"
( (42 in) / 1080 * 9 / ((16^2+9^2)^0.5) / tan( 0.3 arcminutes ) ) in feet = 18.2064165 feet (18 feet 231⁄64 inches)
To calculate at what vertical resolution (or higher), screen size x from viewing distance y approaches "perfection":
Code:
( (x in) / (y ft) * 9 / ((16^2+9^2)^0.5) / tan( 0.3 arcminutes ) )
Example: 42" from 15 feet
( (42 in) / (15 ft) * 9 / ((16^2+9^2)^0.5) / tan( 0.3 arcminutes ) ) = 1310.86
To calculate at which screen size (or smaller), vertical resolution z from viewing distance y approaches "perfection":
Code:
( (y ft) * z / 9 * ((16^2+9^2)^0.5) * tan( 0.3 arcminutes ) ) in inches
Example: Full HD (1080p) from 15 feet
( (15 ft) * 1080 / 9 * ((16^2+9^2)^0.5) * tan( 0.3 arc minutes ) ) in inches = 34.603185 inches
To merely calculate the pixel pitch of your current setup:
Code:
arctan( (x in) / (y ft) / z * 9 / ((16^2+9^2)^0.5) ) in arcminutes
Example: Full HD (1080p) on 42" from 15 feet
arctan( (42 in) / (15 ft) / 1080 * 9 / ((16^2+9^2)^0.5) ) in arcminutes = 0.364128331 arcminutes
Now, here followeth my charts, the first one is in feet:
http://img841.imageshack.us/img841/3733/viewingdistancefeet800x.png
The second one is in metres (British English for the metric system):
http://img33.imageshack.us/img33/8571/viewingdistancemetres80.png
NOTE: These are NOT recommended viewing distances, they only indicate whether a person with very good eyesight, in theory, would be able to benefit from a resolution increase or not.
Myself, I sit 3 meters from my 52" TV. From this we can derive an optimum vertical resolution of:
( (52 in) / (3 m) * 9 / ((16^2+9^2)^0.5) / tan( 0.3 arcminutes ) ) = 2473.41 (or higher)
For people with very good eyesight, even 4k may not be "perfect" in my case.
The point? 1080p is beneficial, in nearly all situations. 4k (2160p) certainly is not useless, in most situations. Also, keep in mind that Blu-ray video is
4:2:0 Y'CbCr and thus 1080p only in luma, whereas chroma merely is 540p. Not only does this mean half as low a vertical resolution (or a quarter as low squared) for the "color" components, it also implies the introduction of chroma scaling artifacts and blur due to the quality (or lack thereof) of Blu-Ray material.