Setup image caption of repeating image field with Toolset post form.
In the form for creating post, you can enable option "Use the WordPress Media Library manager for image, video, audio, or file fields".
When user upload an image, he can upload multiple images in the same image field, and setup the image attributes, including "capiton".
This is the technical support forum for Toolset - a suite of plugins for developing WordPress sites without writing PHP.
Everyone can read this forum, but only Toolset clients can post in it. Toolset support works 6 days per week, 19 hours per day.