As much as I love my Sigma 300/2.8 I have been thinking of replacing it with the Pentax DA*. I wouldn't even think about it if I still had the K7 or an earlier model but the K5 does so well with ISO I feel I can maintain the speed.
Sadly, there is a bit of a difference in subject isolation and DOF between F2.8 and F4 so I would lose that but I would also be losing half the weight.
I'm also a bit concerned about the use of teleconverters. The Sigma AF works great with my Tamron MC7 on static objects, a little slow. ( on moving objects its way to slow ). The Sigma and Tamron 2X MC7 is wonderfully sharp on closer objects so I love this combination when I need to fill the frame.
So this is one of my biggest concerns is losing 600mm 5.6, and as you may know, wildlife is a big part of my photography.
I know I can manual focus the DA* with the 2X but I haven't really seen this combination used much or at alll for that matter.
So if anyone has these I would request please some photo examples.
My decision to switch is mainly portabliity. My health isn't the greatest so its a little difficult to tote this lens around for an extented period of time. I have and I can hike steep canyon walls with this lens mounted and in hand but I would rather only be carrying half the weight.
Having the weather seal of the DA* here in Seattle is a factor also ( RAINY ) and I like to get down to the beaches ( wind and sand ).
So there it is. I just wanted to throw my thoughts out there and see if I could get some example of the DA* 300 with a 2x teleconverter and the Tamron MC4 X1.4.
Thanks for the help in advance.