In most cases, resize them so as not too ridiculously big before uploading. Then let concrete5 take care of it.

The c5 filemanager implements a thumbnail system that in the background prepares the images at various sizes.

These thumbnail sizes are a mix of default, declared by theme, and configured by you in the dashboard.

Blocks on the page use c5 classes to create image or picture elements and internally these use the best thumbnail(s) or create one specially for the use.

Many thanks John,

Sorry to be dim but could you give a rough guide as to what constitutes 'ridiculously big'?!!
:-D

Thanks

Andrew

As the images are for the web, you definitely don't need anything bigger than screen size. Then maybe x2 for retina. But if you are only ever going to be using it a lot smaller, its better to resize closer to how you will use it.

c5 can cope with larger images, but resizing an image consumes server resources proportional to the dimensions of the image (not the file size, so compression doesn't help).

ie. resources required are proportional to image width x height

Servers often run out of resources and fail if an image upload involves a file straight off a digital camera or phone.