Originally posted by awscreo Awesome. Can't wait to try it with my manual lenses!
I think you'll like it. I don't have a K-1, but I have an O-ME53 fitted on each of my Pentax and Samsung re-brand APS-C cameras, and I wouldn't want to be without them. Since it's the viewfinder that's being magnified, the sensor format has no bearing.
I can't recall who, but one of our members isn't quite so keen on the O-ME53 and prefers a third party model. His reason being that it provides a sharper
frame-wide magnification, which is beneficial if you're manually focusing on a subject that's not in the centre of your frame. This makes sense, but I can honestly say I've personally not run into any difficulties with the O-ME53.
I will say, any viewfinder magnifier isn't a panacea for accurate manual focusing. It helps, for sure, but it won't give you the same accuracy as a shim-calibrated split-prism focusing screen or magnified Live View with an LCD loupe (of course, those solutions have their own problems). Don't expect to achieve 100% accuracy focusing an 85mm f/1.4 lens wide open just because you've magnified the viewfinder image a little
But so long as your expectations are reasonable, I think you'll be very happy with the O-ME53