I posted this question in stack overflow, but I think it is more appropriate here:
I have a reference image - 'image_01.png' of size 200x200 and resolution 72 px/in.
I have another image 'image_02.png' (with the same size and resolution) with several levels of zoom, of which, one is close to 'image_01.png', in the sense that the objects in that image are of "similar" size. They are NOT the same images, btw.
Here is an example with three levels of zoom, and clearly zoom_02 is "closer" to image_01 than zoom_01 and zoom_02. My question is, what mathematical metric (ratio, or any measure) do we choose to determine what zoom is appropriate to ensure such similarity? Let's say I even have a screen ruler to measure the distance in the images, in pixels.