I then cropped the image to 1/4 of the total area. (1/2 the length by 1/2 the height). I then cropped that result to 1/4 of its total area again. That means that the crop that you are looking at above is 1/16 of the total origional picture area. The "Image Size" data: Picture size is 1667 pixels x 1226 pixels. (1/4 the length x 1/4 the height).
Does that help?
Is a 100 % crop 10% of the origional surface area? Do you want that? It would be a larger piece of the origional.
Yes, the only way to assess image quality on screen is to look at a crop of the original image, not a resized image.