At the very beginning of the tutorial is a description of the properties of an image.
I understand how an image 2160 pixels wide would yield an image 9" wide at a resolution of 240 pixels/inch.
I understand how that same 2160 pixel wide image could yield an image 6" wide at a resolution of 360 ppi.
Now I fall off the path of understanding. The tutorial states:
"Now, let's say you want to make a larger print — say one that was 14 inches wide. You would then end up with an image that was about 9.3 inches wide but more importantly one that would only have a resolution of 155 pixels / inch. This is not enough output resolution for a high quality print, as we'll see below."
Ok, I understand how spreading that 2160 pixel-wide image over a width of 14" would mean the resolution would have to drop to about 155 ppi. (2160/14=154.2 ppi).
But what does "You would then end up with an image that was about 9.3 inches wide " mean? The image is 2160 pixels wide. At 155 ppi, the document's width is 14". What does "an image that was about 9.3 inches wide" have to do with anything?
Maybe I'm just incredibly thick (my wife sometimes thinks so), but I can't follow this.
Thanks in advance.