Originally posted by audiobomber For maximum range, use the K-1 in crop mode with a Pentax HD 1.4X RC.
Or use one of the crop bodies with a 24mp sensor. Using the K-1 in crop mode is kind of like using a K-5iis (albeit with better AF and better high ISO performance). Even a second-hand K-3 would be worth considering.
Opinions are divided about TC v crop. There is no single right answer. It depends on a lot of factors, including light, subject size and distance to subject. The comparison by WildMark at post #26 above is done with a K-3. It might be different with a K-1, even in good light with the same size subject. It also depends on how big an image you want to finish with. For posting on the web or viewing on a phone, 1200 x 800 pixels might be enough. But most DSLR users are probably going to want more than that (certainly if you want to print at more than 6x4).
Originally posted by desert-tiger Ah well, think they are coming out with a ff one?
Don't bank on it. It's not on the Pentax roadmap.
Originally posted by desert-tiger What about the Tamron-F AF Tele-Converter 1.4X Pz-AF MC4 Teleconverter for Pentax K KAF3 Mount | eBay
My personal view, from experience, is that a decent TC is a worthwhile tool for birding, particularly with a 300mm f4 or f4.5 lens (or faster), just as a 400mm f5.6 lens is a useful tool. In fact since I got the FA*300 f4.5 and Kenko Pz-AF 1.5x Teleplus SHQ (i.e. the one that is said to be the twin of the Tamron which Mark tested, rather than the Kenko used in Mark's test), I don't use my Sigma 400mm f5.6 tele macro very much. The IQ is better with the FA*300 + TC (effectively 420mm f6.3), even though the Sigma is quite a good lens and one-third of a stop faster.
But the returns diminish when your effective maximum aperture goes beyond f5.6 or f6.3 - from trying it, I'd need to have a compelling reason to use the Sigma with the TC again (for an effective 560mm f8). Some people have got good results with the DFA 150-450 at maximum reach with a TC (effectively 630mm f8) - good luck to them. But you'd need ideal conditions.
The Kenko works very well (on the K-3) with the DFA 100 f2.8 macro WR (effectively 140mm f4).
Last edited by Des; 02-13-2018 at 05:16 PM.