Max image size is 6MB.
The recommendation is to upload as high-quality images as possible, and dimensions should be 2560 × 1708 pixels or greater. The CMS will then automatically crop the image to the correct size for different modules and optimize image size preserving the image quality.
If the image doesn't look good in the module you are using (focus is off), try editing the image's focal point, which by default is in the centre of the picture.
Image ratios for different modules:
Hero video, the perfect size for background video is 1920x816. Preferably it should not contain any text, and it should be cut so that it loops smoothly. Video needs to be loaded on Vimeo in order to work correctly (YouTube doesn't work).
Contacts with image
Image + Text
Lift-up block with image (M-L)
Latest/rel. publication with image (M-L)
Latest publications with image (Small)
Products/services with price
Products/services without price
Related products with price
Related products without price
Full image, no style, used as a CSS background image
Campaign/promotion banner with image