I am searching for an _own_ field, maybe xmp, but not something like one of the comment fields and I don't care where, to put in a value like. "1.52". I try to explain, what this value is for. Assume you took a shot with a focal length of 100mm with a given resolution. Then I crop the photo by cutting of the border. The result would be the same as the photo has been taken with 100*1,52=152mm and original resolution. (of course the resolution is now smaller because of the crop, it is a theoretical value). I have found xmp-fields like CropBottom, but no field which fits for this. I would like to use existing fields, not an own xmp-field. Any ideas? I nead this field for a query later.