Oxy gallery with ACF and Lightbox enabled

[MimiDev]

When using the Oxygen gallery (with the ACF option (from an ACF gallery)) and the Lightbox function enabled, the image displayed on the frontend, by the Lightbox, is the full size image - which can be very (unreasonably) large at times.
Is there, or can there be, a way to limit the size of the image displayed in the Lightbox on the frontend?

While we can select the thumbnail image to display in the 'grid', we can't select the size of the image displayed in the Lightbox (unless there's a setting I've missed).

Thanks