Quote Originally Posted by glogan View Post
My non-mathematical understanding is that 'optimum' is that, because, if the hole is larger, then excess unfocused or incoherent light rays are allowed and begin to blur the image; and if the hole is smaller, diffraction begins to blur the image.

So the optimum hole size is the least blurry point between those 2 causes of blurriness.

Does that sound accurate to others?
I understand that there's a median point in between those two to get a good result. My question still stands and to why it has to change for different focal lengths. I have a pinhole that works wonderful on a home made pinhole camera that takes a 4x5 negative. Why couldn't I transfer this pinhole to another camera with a longer focal length. Sorry if someone already answered this in their response. Maybe it's just all going over my head and I should let it be what it is. There's a reason I'm an art major - hahah.