Ismael,
That was exactly the problem, or other than a problem something me (newbie) haven’t seen. Thank you very much.
Have a great weekend.

Hi Basilis, thank yo for your answer.
Unfortunately I’m testing in a VM before uploading to the website, but I’ll explain step by step:

1) I’ve imported “Startup business demo” to work as a base .
2) When editing the home page, there is a section with an element “Image with hotspots”.
3) I’ve uploaded an image of size 1920×1080 (collage.jpg), to replace the original in the demo.
4) When I check the wordpress directory wp-content/uploads/2015/02 , along with many other images, I can see my own uploaded image but in many versions.
> ls collage*
collage-1030×579.jpg collage-1500×430.jpg collage-180×180.jpg collage-36×36.jpg collage-495×400.jpg collage-768×432.jpg collage-845×684.jpg
collage-120×120.jpg collage-1500×630.jpg collage-260×185.jpg collage-450×253.jpg collage-705×397.jpg collage-80×80.jpg collage.jpg
collage-1210×423.jpg collage-1500×844.jpg collage-300×169.jpg collage-450×450.jpg collage-710×375.jpg collage-845×321.jpg

5) When I check the page using my browser (Safari, Chrome, Firefox), I see the image awfully rendered.

6) I open the image in a new tab, and see that the problem is the theme is using collage-300×169.jpg, instead of another larger version, more appropriate regarding the screen size.

7) Couldn’t find any option to “tell” Enfold to use the largest image possible for the screen size.

Suggestions?

Thanx!
S

Vinery thank you for your answer.
I did exactly as you say, changed wp-config.php, added a php.ini in the wp-admin directory..
Somehow it doesn’t work, always the error importing the demo, but somehow the error log is empty.
Any other thing I can do?

Best,
S