Suppose I look at the moon, how many photons are needed to see the full moon or does 1 photon contain the entire information of the moon?
In other words, can a photon be compared to a pixel of a photo or is it more?
Answer
An image (of the moon) consists of a large number of pixels.
A pixel is a “value”, a number. A pixel in common image formats (JPEG, GIF, BMP) is an 8-bit number, or 256 gray levels (where 0=black to 255=white). In a color image you have a gray value per color (red, green and blue). In the better cameras you have more gray values, somewhere between 1,000 to 10,000.
A step in grayscale represents a number of photons. In most sensitive astronomical cameras you will easily have 2 to 10 photons per step in gray value. In ordinary cameras you need more than 100 to 1,000 photons per gray level.
A photon can be compared with a very small step in the gray value of one pixel.
Answered by
Engineer Bart Dierickx
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