The photo made with pinhole is blurry and hard to see in reality is because the amount of light emitted from the object actually passing through the small pinhole is very small compared to the overall amount of light emitted. Larger pinhole permits more light, but also leads the problem called "circles of confusion".
is the blurring effect from the pinhole's loss of light applied uniformly or more concentrated around the edges? and how come the pinhole image appears so grainy such that some parts of the light are lost while others aren't? what determines which part of the light is lost?
I would say the blurring effect from the pinhole's loss of light is more uniform based off of observation. I think some parts of the light are lost just by chance based off of which ones enter and don't enter.
prof. ng explains in lecture that the blurring effect of the pinhole image is due to diffraction of light passing through the pinhole, while larger lenses can produce sharper images of the subject but blurrier backgrounds. the blurriness comes from diffraction and the noisy/dim nature of pinhole images is from the overall lack of light.