I've been using a 5D2 since 2012 and have always been able to get the shot, though I have encountered minor frustration with the outer AF points in low light. I have no complaints about the IQ, and I personally find ISO 6400 perfectly useable. That said, this summer I'm going on a possibly once-in-a-lifetime trip, and I'm wondering if it would be worth it to buy a 5D4. As I said, I've never been in a situation where the 5D2 couldn't deliver, so deep down I know I don't need a 5D4. But it is an improvement in every way (unlike the 5D3 & 6D2), and I have a feeling the GPS could come in quite handy. I just struggle to justify spending the money when I know my 5D2 can get the job done. I considered renting but nixed that idea because I'd just as soon put the money towards buying the camera. Another consideration is that I planned to buy a 5D4 eventually, but at the final clearance price. The current street price (new w/ USA warranty) is hard for me to justify, though it might be worth the splurge to have it for my trip?
Keep 5D2
Plus, it's a two week trip, so plenty of time for everything... and she wants to hike a volcano, which means I'm definitely bringing a camera to the top!


