When you decide to post content on your website, the theme automatically generates thumbnails from the featured image to display the content on your pages in an attractive way. This process creates 17 different thumbnail sizes. To make you website faster, you can control which thumbnail is generated. To do this go to Theme Panel > Block Settings > Thumbs on modules & blocks and disable the unused ones to save space on your server:
Default thumbnail placeholder
If the thumbnail image is not enabled for a specific module that you use, the module will show a default placeholder with the size of the image and instructions about how to enable the thumb for that module.
Modules and thumbs
Uploaded Image Size
WordPress doesn’t have an upscale function, if you upload small images on modules that use thumbs that are larger than the uploaded image the original size will be used (the image will not be up-scaled), this is not ideal because blank space may appear around the thumb.
There’s no ideal image size for cropping, a part of the image will be lost due to aspect ratio differences. On the Newsmag theme some modules have a 16:9 aspect ratio, while others have one closer to 4:3.
Example 1: if you upload an image that has an aspect ratio close to 4:3 the cropping function will cut the bottom on thumbs which have a 16:9 aspect ratio.
Example 2: if you upload a 16:9 image the function will cut a portion from the sides for the thumbs that have an a 4:3 aspect ratio.
Depending on the module used, the best solution is to experiment with different sizes and see which one offers the best results.