Originally posted by mrt10x I have the 50-500.. it is HUGE.... and HEAVY!!! If I was going to do it all again I would get a 70-200 2.8 and a TC. CW on BIGMA is that it really isnt very usefull beyond 420 or so anyway. So with the 70-200 2.8 you have a really nice, fast lens, that will still reach out and touch something with a TC at about the same speed and usefull length as BIGMA. Filters for the 50-500 cost an arm and a leg as well. IMHO
edit: it is also a pretty slow focusing lens as well.
I bought the origonal sigma APO 70-200 F2.8 EX when I bought my *istD. Since then I have added 1.4x and 2x Sigma TCs. every time I think about going longer, I look at the bigma, and decide almost instantly that it is NOT fast enough to replace my esixting options. With a 2X TC on the 70-200, I get 400mmF5.6, Half a stop faster than the Bigma, and on the K10 I have seen any point in accepting the need for a higher shutter speed (due to longer lens,) and loss of 1/2 stop on maximum apature. I know the K10D has image stabilization, but nothing helps sharp images more than shutter speed.
For me, the 70-210 plus TCs is a much better option, especially when you don't need the extra length, take of teh TC and get a whole bunch more shutter speed due to the F2.8 maximum apature.
as for image quality of the origonal 70-200 F2.8, I have referenced the link to these photos many times.
https://www.pentaxforums.com/forums/187646-post19.html https://www.pentaxforums.com/forums/208249-post1.html
I also have an option at 500mm, less than 1/2 stop slower than the bigma, specifically SMC 300 F4 and SMC-F 1.7x AF TC.
if you are reasonably close, it is a stand out.
https://www.pentaxforums.com/forums/106132-post4.html
for me, if I buy a new 500mm lens (or combo) it needs to be more than 112mm in diameter