How to Change Default Image Sizes
Whenever you use the WordPress Media Uploader to insert a new image into a post or page, WordPress automatically creates three different versions of that image: a thumbnail size, a medium size, and a large size. What this means is that if the original size of your image happens to be super-large (such as an image taken with a digital camera), WordPress will automatically resize that image to the default image sizes that you have setup on your WordPress Media Settings page.
In this video I’m going to show you how to change those default image sizes, and how to insert a thumbnail gallery into a WordPress post or page.
Tags: default, gallery, image, insert, resize, settings, size, upload