Change "Photo" to "Image"
For English, photo and image words are very similar but it's not the same for all languages.
Scan menu has the "Image" and "Text" options. Due to this word choice, I suggest changing these sentences from "photo" to "image".
Current sentences.
#: src/preferences-dialog.ui:318
msgid "Photo Resolution"
#: data/org.gnome.SimpleScan.gschema.xml:50
msgid "Resolution for photo scans"
#: data/org.gnome.SimpleScan.gschema.xml:51
msgid "The resolution in dots-per-inch to use when scanning photos."
#: data/simple-scan.appdata.xml.in:9
msgid ""
"A really easy way to scan both documents and photos. You can crop out the "
"bad parts of a photo and rotate it if it is the wrong way round. You can "
"print your scans, export them to pdf, or save them in a range of image "
"formats."
My suggestions.
#: src/preferences-dialog.ui:318
msgid "Image Resolution"
#: data/org.gnome.SimpleScan.gschema.xml:50
msgid "Resolution for image scans"
#: data/org.gnome.SimpleScan.gschema.xml:51
msgid "The resolution in dots-per-inch to use when scanning images."
#: data/simple-scan.appdata.xml.in:9
msgid ""
"A really easy way to scan both text and images. You can crop out the "
"bad parts of an image and rotate it if it is the wrong way round. You can "
"print your scans, export them to pdf, or save them in a range of image "
"formats."