As far as I understand it, “Save position & zoom” will do just that for the current picture. From the F-Stop Tutorial:
For example, if you don’t like the layout of an image you could crop it but that would change the original image. Instead, you can zoom and position the image as you like and then save it using this feature. After it is saved, the image will not be changed on your memory card but it will always be opened in that particular zoom and position — just as if the image had been cropped.
“Lock position & zoom”, on the other hand, also temporarily keeps the position & zoom when switching between images, similar to the free program “XnView MP” on PC/Mac/Linux. This is useful for choosing between similar pictures while being zoomed in on a specific region (a face, for example).
Note: “Lock position & zoom” sometimes doesn’t work for me, I don’t know why.
