A tap of the EXIF metadata text to show to a second metadata view, containing Lightroom sync information:
To the right of the non-editable metadata display, is a histogram which shows the primary red, green and blue (RGB) color channels. Tap the histogram display to toggle between showing the RGB histogram and a greyscale luminance histogram.
In the column on the left-hand side of the photo in Loupe View, you will see information specific to the Mode you’re in. While in Catalog Mode (Section 3.3), you see which User Collection you’re browsing. In Metadata Tagging Mode (Section 3.4), you see a list of all editable IPTC Metadata. When in Export Mode (Section 3.5) shown are all the services to which the currently displayed photo may be sent.
While in Loupe or Grid Views, the configuration options shown while in Dashboard Mode (Section 3.6) are more broad in nature, and are not applicable to the currently displayed or selected photo(s).
Pinch and un-pinch to zoom and un-zoom as you normally would in iOS, by using your thumb and index fingers. A double-tap with a single finger will toggle zoom levels between fit-to-screen (to display entire photo) and zooming to 100% resolution.