Originally posted by borno Hey Daniel,
I was using the 1.5x pz shq on my DA*300mm and it didn't work, I ordered another to try as others had luck with theirs. I have been using the 1.7x afa and have even stacked the afa and the kenko 1.5x and it focused ok with the screw drive so I'm puzzled. I will give it another go with another one and if it doesn't work I'll sell one of them.
Tom
Sorry to hear that . I can only speculate that your combo (DA*300mmF4) is just below the cut off where not enough light has gone through. The difference of F2.8 (re DA*200mm) & F4 (re DA*300mm) could be very critical.
All these combo are not custom match by design . All it takes is just one element (of many) off by 1 mm. Hope to hear good news from you as a lot of DA*300mm owners would love to hear that. Or you have to wait for the new Pentax rear custom TC to come out. Well , it will not be cheap though
Daniel