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Name: Herbert
Status: Educator
Age: 16
Location: N/A
Country: N/A
Date: Around 2001


Question:
Presently there is quite a bit of talk about pixels. Each digital camera manufacrer claims there camera has 3 million pixels, another 3.5 million, on and on. This reminds me of the 50's & 60's when Hi-Fi audio manufacturers claimed there equipment had a wider bandwidth than its competitor. So the question is what is the resolution of the human eye, and can the figure be quoted in pixels?



Replies:
I will answer as much as I can, but your questions about the limits of the human eye should really be directed to a specialist in the theoretical limits of the human eye. Right now that is a question that has been researched quite well, and there are several formulas to help predict that.

From what I understand, the resolution of the human eye is not measured directly in pixels, but by the angular difference between two points of light that can be resolved. Here is a very good article on that:

http://www.madsci.org/posts/archives/may97/864446241.Ph.r.html

From this article, if I have done the math right, I understand that a typical person has a maximum resolution of about 17000 point sources per inch. This doesn't really equate to pixels, but, pixels can be changed into pixels per inch, and that should be close enough.

Digital cameras do brag about their resolution, because, well, it really does matter. It matters because their resolution is so poor compared to a real cameras, or a decent printer that it is pathetic.

For example, a really good digital camera might have a resolution of 2160 x 1440. If you made that into a 4x5 picture, you have a resolution of about 400 pixels per inch. Which isn't bad, but photo quality printers print at 2400 pixels per inch. If you decided to make it into a 8x10 photo, you end up with about 200 pixels per inch. This was considered excellent quality 10 years ago, but is very poor quality by todays standards.

So, compared to the human eye, a real camera, or good printed material, digital cameras aren't there yet. They do use a wide variety of software to try and enhance the quality for printing, but there is still room for improvement.

That doesn't mean digital cameras don't have a use. If you need pictures in a digital form to be displayed on computer screens, then you have something. A computer screen has a resolution of about 72 pixels per inch, and digital cameras are definitely better than that. Also, since it is basically one step from taking the picture to downloading it onto your computer, you get better results than if you took a picture, developed it, and then scanned it in, not to mention much faster results. With the popularity of the web, digital cameras are great for creating images to place on a web site.

I hope this helps.
--Eric Tolman


http://www.madsci.org/posts/archives/may97/864446241.Ph.r.html

From this article, if I have done the math right, I understand that a typical person has a maximum resolution of about 17000 point sources per inch. This doesn't really equate to pixels, but, pixels can be changed into pixels per inch, and that should be close enough.

It would seem to me that if the resolution of the human eye is one arcminute at 10 inches, then the maximum resolution of the human eye is found as follows:

You find the circumference of a circle of radius 10 inches, which comes to 62.83 inches. One 1/21600th (or 1/60th of a degree) of this is 0.002908 inches, the minimum possible perceptible distance by the human eye at 10 inches.

To get this much resolution, you need 343, not 17,000 pixels per inch.

Of course if you get even closer, the story changes, but what the resolution of the human eye is at some other point that 10 inches I am not sure.

Even taking a hypothetical one inch of distance with the exact same eye resolution we still only get 3400 dpi, far short of 17,000.

Thanks,
-Josh Hug


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