Sigma 120-400 experiences

Hi all, has anyone had experience of the Sigma 120-400, or even the 150-500 as I want to step up from my Pentax 55-300 and the 60-250 may be a touch out of my budget.
I have a K5 and feel I can more out of this camera with a better lens, I do mainly 'walkabout' photography.

I have both - both great lenses - the 120-400 is a shade faster and seems to focus slightly quicker and is easier to hand hold. IQ is virtually identical and you do of course have the longer reach with the 150-500

I had the 120-400 first and then bought the 150-500 for the extra reach intending to sell the 120-400 but I have not managed to let go of it - it does have it's advantages over the the 150-500.

I can't justify keeping both - really must get around to offlaoding one of them!

Carl

I have the 120-400 very easy to hand hold great for walk along canal but still have not caught sight of that bloody heron

I have the 150-500 and for the money is a superb lens, Much faster focusing than the 55-300. Not to easy to hand hold, but a monopod soon sorts that out.

I have the 150-500, purchased a few months ago from SRS. It has rendered my old Sigma 600mm mirror lens redundant. I've managed to capture lots of good images of birds as well as one or two other interesting shots. It is a heavy old beast, but the OS systems (lens OS AND K5 SR working in tandem , as well as, of course, my rock-steady hand :wink produce some remarkably sharp images right up to 500mm.

How it compares with the 120-400, I cant say but have a look at the bird shots in my gallery for sample shots.

B.

I have both the 55-300 and the 120-400 Sigma (older HSM version) and use both on a Pentax 5iis. I first used the Sigma on my K7 and I was not entirely happy with the results, however on the K5ii it performs very well, over all better than the 55-300, especially on focusing. I tend to carry the 18-135 with the 120-400 to give a full range, only taking the 55-300 when I want to travel light and tacle birds in flight - much easier to pan with the lighter lens. Though recently (yesterday!) I left the monopod at home and used the 120-400 hand held! I was most impressed.

I have tried both with my Kenco 1.5 teleconverter and found the Sigma to be very soft, especially at 400 (equivalent to 600) so will not use that combination again, will just crop!