I'm new to EOS. JDM said "Friends don't let friends buy chipped adapters" and explained the risk that a fishy chip might fry the AF electronics. OTOH: I have a 5D IV, AFAIK there are no conventional user exchangeable manual focusing screens available for it + I've never been great at eyeballing SLR focus, so using it's multitude of AF spots behind adapted heritage lenses too feels very tempting to me. My big question at the experienced community: Which old and inexpensive EOS body should I get, to test my adapters on, before I'll wager the 5D? Is there something dirt cheap that uses the same batteries? According to my current understanding 50 Euro should buy me a working 300D. Whatever I might save on a film cheapo will most likely get eaten by a new battery? An original 5D does tempt me in general but seems a bit too expensive for that purpose. Thanks in advance for any input!