What rights do I need to set for a contributor to be able to upload images to the custom post type with the front end editor? I only want them to be able to edit their own custom post types and so far the image upload only seems to work when I enable almost all permissions..
What type of field is this, an image field or a gallery field?
Image fields should work, gallery fields require access to the media library.
It is the gallery field, we’d like users to be able to upload multiple pictures at once.
There are two choices
1) Use a repeater field, create an acf/save_post action that copies the images from the repeater to a gallery. This would be my choice because it’s more secure.
2) Give contributors access to the WP media library. There may be a plugin that can do this. Here’s one that I’ve never tried https://wordpress.org/plugins/members/. Either you’ll need a plugin that allows it or you’ll need to start searching for code to do the same thing.