Megankeagles

Hi there, I am a keen and experienced user of my trusty (but heavy!) Pentax 645. I was wondering if there were any recommendations for a more lightweight option for day to day / holidays? I am aware that lightweight generally means a rangefinder lens, but I don't have much experience in this. So I am ideally looking for a lightweight SLR or an autofocus rangefinder. Is there anything good out there that could be recommended? Many thanks! Meg