Thought I'd picked up a winner at the flea market a couple weeks ago.
Pentax H1a looked good... Even at 500 I could see crisp and clear sky through the back from edge to edge.
Was thinking about getting a strap and taking it out... Tried 500 again a few frames and at first, crisp and clear. Then a dark start.
Fired a couple more and saw it occasionally dark start and also a couple frames dark in the middle.
Hate when that happens.