Sometimes you’re happy playing around with CSS, tuning up an astonishing theme, when you discover that some images are been rendered with a lot of blurry.
Probably, the theme its using the thumbnail size for your image, instead of a bigger one, and chances are that your box size for displaying image its mach bigger.
First thing to do its go to “Settings / Media” on the left menu bar from wordpress admin panel, and adjust the size for thumbnails, medium size, and large. Depending on the theme in use, that should work, or not.
Second thing and a must its install “Regenerate Thumbnails” plugin, that exactly does what its name indicates: Regenerate all the media library.
But, this should not work at all with some themes.
That’s the moment to look for functions.php file on the root folder from your them.
Then open it, and look for add_image_size . You’ll find some different use cases, edit it like on the image below and adapt it to your needs:
After this modification, please remember to reload thumbnails again with the plugin.
Some themes needs a lot of work to personalize it properly, but almost everything is possible with patience and some research.