Testing The Resolution of the Human EyeAuthor: Ethan Ace, Published on Dec 04, 2013
All sorts of wild guesses and theoretical calculations exist about what the resolution of the human eye is, with 576MP a common claim.
No one we can find has ever actually tested it . . . until now.
In this report, we share our findings of testing various resolution IP cameras against the human eye.
Here's a summary of the full test results, explained inside the report below.
We used the Snellen Eye chart as a baseline. A human is considered to have 20/20 vision if they can read line 8 on the chart from 20 feet away.
The goal then is to find what camera, with what resolution, could 'read' / 'see' the same line, same distance on that same chart to see if it could be as good as the human eye.
We took a series of IP cameras (720p, 1080p, 5MP, and 10MP) and set them to a 60° angle of view. While humans have wider peripheral vision, in our testing this 60° range represented the area of main vision.
Just like a human, we placed the cameras 20 feet away from the Snellen eye chart (pictured below) to see what the camera's "eyesight" would be and whether any cameras could match or beat the human eye.
We began with the four cameras in well lit room, about 160 lux. The image below shows the full field of view in this scene.
First, the 720p camera was only able to resolve about line 4 on the Snellen chart, equal to about 20/50 vision.
1080p resolution was able to read only one line further, to line 5, 20/40 vision.
And moving to 5MP, one line is clearly gained, 20/30 though one may contend that the next line 20/25 is also readable.
Finally, 10MP provides a further jump in resolving power, able to read line 8, equal to 20/20 vision in humans.
So that's it. In ideal even bright lighting, a 10MP can match (or maybe even slightly beat) a human eye.
Dimming the lights in the room to approximately 3 lux, we tested again. At this light level, multiple human test subjects with 20/20 vision were able to make out line 6, 20/30 (EDFCZP), a two line reduction in ability from the brightly lit room.
720p resolution was only able to view down to line 3 (20/70) in this case, due to increased noise and a dimmer image.
The 1080p camera did not fare any better, with even more increased noise and artifacting obscuring lines below 3, actually making letters slightly less legible than in 720p.
At 5MP resolution, line 4 (20/50) was legible. Note that some letters of line 5 are clear, but noise and artifacts do not allow the full line to be easily read.
Finally, the 10MP camera was able to read down to line 5, 20/40. Again, some letters on line 6 are easily legible, but we cannot conclusively claim all of them are clear.
For our final test, we lowered the lights to approximately 1 lux, a very dark room. At this light level, only the 720p and 1080p cameras produced usable images of the chart. Human subjects were able to make out line 5 on the chart, equal to 20/40 vision (PECFD).
The 720p camera was able to resolve line 2, equal to 20/100 vision, with others below becoming unclear.
And moving up to 1080p resolution, line 3, 20/70, can be read.
The 5 and 10 megapixel cameras produced only a nearly black image and noise. So let's call them 'blind' in low light.
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