Internal Server Error (500) When uploading new image

[Bentronics]

I am getting Internal Server error (500) when adding a new item to my website.
It happens when I try to add an image to the item.
When I click on preview it takes a second and error message occurs.

[kobra]

Please provide information in the posting tips at the top when you reply

[mc12345678]

As a friendly reminder/note seeing that this appears to be the first post as a forum member:

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Also some details about the image(s) might help like the resolution. Are you using an image handler, etc..

[DrByte]

Also, there are these FAQ articles on common causes of that symptom:
Getting 500 or 406 or 404 or 403 errors when submitting product updates in admin pages
Why Am I getting 500 Internal Server Errors