getting image alt text via ACF plugin in WordPress [closed]

You need to set your ACF field to return the image object instead of the URL. You can then use the following code to retrieve the image and alt text:

<?php $slideshow_image = get_field('slideshow_image');
// Check for alt text - if there isn't any, use the image title
$alt = ($slideshow_image['alt']?$slideshow_image['alt']:$slideshow_image['title']);
// Return full size image
$url = $slideshow_image['url']; ?>
<img src="https://wordpress.stackexchange.com/questions/161190/<?php echo $url; ?>" alt="<?php echo $alt; ?>" />

If you want to return the image at a different size, you can use the sizes array instead of the url:

// Return image thumbnail    
$url = $slideshow_image['sizes']['thumbnail'];

Documentation here under Customized display: http://www.advancedcustomfields.com/resources/image/

EDIT:

This solution works for ACF 3.3.7 and above only. Another method is to return the image/attachment ID, then use wp_get_attachment_image() to return the full image HTML.
Documentation here: http://codex.wordpress.org/Function_Reference/wp_get_attachment_image