Milan Dinić

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Image descriptions are stored as content (field <code>post_content</code>) while captions are stored as excerpt (field <code>post_excerpt</code>). This means that descriptions are shown on single attachment pages, while captions are shown in <a href="https://codex.wordpress.org/Gallery_Shortcode" rel="nofollow ugc">galleries</a> and if image is embedded in a post content with a <code>[caption]</code> shortcode.
If you use images just in galleries, in order to have text below image in both places, you need to fill both fields.
This plugin changes that. You only fill description field and that text is used as caption of image in galleries.
There are no options or settings, just enable plugin and everything works automatically.

Descriptions as Captions in Galleries

Show image descriptions as captions in galleries.

webdevstudios

Michael Beckwith

Justin Sternberg

pluginize

Jetpack has a pretty robust Image slideshow feature. (If you don’t know, “Add Media” button > “Create Gallery” > Choose photos > “Create new gallery” > Change type to slideshow in “Gallery Settings” > “Insert Gallery”)
Make sure you have “Compose using shortcodes to embed media from popular sites” enabled in “Settings” > “Writing” > Composing section of Jetpack settings.
Jetpack’s handling of photo’s captions doesn’t work well with long captions (as it overlays the caption above the photo). This plugin modifies the layout so that the caption is displayed below the photo and the slideshow expands to accommodate.
Contribute on <a href="https://github.com/tw2113/Jetpack-Slideshow-Caption" rel="nofollow ugc">github</a>.
Slideshow Captions for Jetpack is not maintained by Automattic.

Slideshow Captions for Jetpack

Modifies Jetpack's default slideshow caption feature.

Descriptions as Captions in Galleries vs Slideshow Captions for Jetpack