Access to original image rather than to backend sizes

[AJ1234]

Hey.

Instead of references like:
{$product.cover.bySize.medium_default.url}
which correspond to eg. the following file:
123-medium_default.jpg

How to access the original file 123.jpg? The $product variable doesn't seem to contain its URL.

Edit: alternatively, more generally, my issue is that I want images' full sizes to show after clicking the product picture on product page. I tried defining a huge size (like 2000/2000 px) in the backend, calling it eg. 'maximum', and having the theme open it, like this: {$product.cover.bySize.maximum.url}, but upon generation of this size, it turned out that Presta pads original images with white -- that is, that a size's defined dimensions are strictly enforced, rather than being a mere limit that is not to be exceeded.

Edited October 14, 2020 by AJ1234 (see edit history)