- Image 1 Field: the name of the field which contains the primary image
- Image 1 Field Backup: the name of the field which will be used if Image 1 Field does not contain an image. Typically this will go to the body style and look for a subfield which contains a default image. The current value (in N Scale Trains) is Complex_ProductPrefix_DefaultImg. The engine parses this to mean, if you cannot find an image in Image 1 Field, then look at the "Complex" field called "ProductPrefix" (Body Style) and try to find a subfield called "DefaultImg" and use the url you find there as an image for this item.
- Image 1 Caption Field: The name of the field to look inside to find a caption.
- Image 1 Empty Text: If Image 1 Field was empty, and you were required to use the backup image, then place this text into the caption.
So as you see, the engine uses these control fields to select which item fields are used for captions for image1 and image2.