Well, I wasn’t thinking about getting a repeater in that fashion, I was assuming that you’d be using a ‘while(have_rows())’ loop.
You have several choices. You can get the entire repeater with no formatted values
$rows = get_field('slider', false, false);
and then do all the formatting yourself,
or you can get the repeater twice
$formatted_rows = get_field('slider');
$unformatted_rows = get_field('slider', false, false);