Jonathan Desrosiers

In WordPress 5.3, several improvements were made to how images are processed. One of these improvements was the concept of “BIG images”. When an image is uploaded that exceeds the “BIG image” threshold (2560 by default), a new “full” size image is generated. This new image is then used instead of the true original when generating image subsizes to reduce server load.
Prior to 5.3, it was possible for the originally uploaded image to be displayed on the front-end, even when they were not “web ready”. Unnecessarily large images can be bad for performance and wastes bandwidth (which is unfortunate for those with slow Internet, or bandwidth caps by their service plans). This new full size image will now be displayed instead.
There are some scenarios where disabling this threshold would be desired, though. Maybe you run a photography site that 
needs to display original images, or your theme has full screen backgrounds.
This plugin disables the “BIG” image threshold and preserves the true originally uploaded image as the full size.
For more information on the improvements to image processing in WordPress 5.3, check out these <a href="https://make.wordpress.org/core/2019/10/09/introducing-handling-of-big-images-in-wordpress-5-3/" rel="nofollow ugc">developer</a> <a href="https://make.wordpress.org/core/2019/10/11/updates-to-image-processing-in-wordpress-5-3/" rel="nofollow ugc">notes</a> on the <a href="https://make.wordpress.org/core/" rel="nofollow ugc">Making WordPress Core blog</a>.

Disable "BIG Image" Threshold

Disables the "BIG image" threshold introduced in WordPress 5.3.

codecide

The Image Size Manager plugin allows site administrators to configure the automatic scaling of large raster images in WordPress.
Since version 5.3, WordPress automatically scales down images whose size exceed 2560 pixels in either width or height. The resized images are renamed with the “-scaled” suffix in the media library. However, automatic rescaling can conflict with the intent of the website’s author(s). Your favorite CMS does not provide administrators with a way to disable this “feature”,nor does it allow users to modify the size at which the scaling kicks in. See <a href="https://make.wordpress.org/core/2019/10/09/introducing-handling-of-big-images-in-wordpress-5-3/" rel="nofollow ugc">this thread</a> for details and an extensive discussion.
Image Size Manager provides both options with a simple, straightforward interface. 
* Access the configuration option from the sidebar menu named after the plugin. 
* By default, simply activating the plugin disables the automatic scaling of “big” images. 
* Note that since WordPress 5.3.1, the automatic scaling feature of WordPress ignores PNG files. Hence, this plugin has no effect on PNG and only affects other raster image formats such as JPEG, TIFF and similar. 
* Image Size Manager has been tested extensively, has no side effect, and should work with any existing theme or plugin.
This plugin will be updated to account for changes in future versions of WordPress, if necessary. Other features, such as configuring additional image sizes generated by WordPress, will be available later.
If you encounter any problems with the plugin, or need extra related functionality, feel free to contact the authors through the comments or the official plugin page.
<h3>Donations</h3>
None needed.

Image Size Manager

The Image Size Manager plugin allows site administrators to configure the automatic scaling of large raster images in WordPress.

Disable "BIG Image" Threshold vs Image Size Manager