Optimal image sizes
All images are optimised by the system and scaled/cropped into the right sizes. The only time we use a separate image property for mobile is on the campaign page and that’s because we sometimes want a slightly changed image composition on mobile. For example see the changes on the Lurpak Natural Claims page: https://www.dropbox.com/s/v6qvgtr4ye8iyqo/Screenshot%202016-08-29%2014.03.41.png?dl=0
On the campaign page you can set the height yourself but the are 1880 wide (desktop) and 767 (mobile) and on desktop is not full bleed for a couple of reasons. Both from a tech perspective but also in regards to content. Since we’re not adding a shadow to make the text more accessible it’s up to the editor to make sure the content in the html property is shown properly. If the image would scale depending on the browser size that would be one more factor to consider when making the assets and content.
In the image segment (which we have on the start page) The image is cut to 1620x1000. This image is full bleed and how much is showing is depending on how long title, subtitle and if you have a button.
A good rule of thumb is to always try to upload a rather large image (~2000px) because then it’s possible to use it everywhere. If you use it in the blog it will be optimised and scaled for that and if you use it in an image segment it’s scaled for that. If you don’t have the image in high resolution you should at least upload the image ~1000px for use in the blog etc like you mention.