[Bob from Aus]

My Sigma 50-500 is only just OK. 500 at infinity is crap. If you want fabulous photos much of the time, you will probably find you will want to upgrade from a sigma zoom. So the big question which of the options provide your needs with the best upgrade. There are some good suggestions above.

My replacement ended up being
Sigma 500 prime - sensational lens
Pentax 60-250 - my copy is brilliant (but with the new pentax TC its rather ordinary)

[lesmore49]

I have a Sigma 150-500. I don't have a 50-500 Sigma, nor do I have a Pentax 150-450, so I can't set up a test with these three lenses and come to a conclusion, using my best assessment tool...which is my eye. I do read tests and while they are helpful, I find the best assessment tool is my eye, looking at the final product, a photograph taken with a particular lens and camera body.

So far with over two + years of personal experience and many photographs, I have found my Sigma 150-500, coupled with my Pentax K-5 body, capable of taking extremely sharp photographs.

I find that camera / lens settings are very important in getting the best photograph with any large, heavy super telephoto lens. Proper F stop, shutter speed, ISO, support method used, etc. are all critical.

My practice is not to make any public assessment of piece of camera equipment, that I have not actually used extensively.

[biz-engineer]

The Sigma 50-500 and 150-500 are f6.3 at 500mm. Stacking a 1.4 AND 2x TC on the 70-200, aside from some rather bad image loss, becomes a 560mm f8. Not even a close comparison and there's a VERY good chance the camera won't even AF with that combination. The 1.4x TC is a great TC, so you can get away with that on good glass, but I have never ever found a 2x TC worth putting on any quality glass. The math doesn't add up and the results will be very disappointing. What makes my two cents worth anything? I've owned the 50-500, 150-500 and now own the 150-450. I have also owned the Pentax 1.4x, Tamron 1.4x, Sigma 1.4x and 2x and the Kenko/Vivitar 1.4x TC. I've tried just about ever combination of long lens out there except the DA 560mm. My opinion: The 150-500 is better at 500mm than the 50-500, but the 50-500 is better UP TO about 400mm. The 50-500 is actually closer to a 50-460ish if i remember the exact specs in terms of magnification, whereas the 150-500 is pretty close to 500 at 500. AF performance on the K5iis and K3 is slightly better for the 150-500 than the 55-300 but that's not saying a whole lot. It's slow for wildlife. The 50-500 AF is slower and less consistent than the 150-500. The 150-450 is in a different league and for the price it better be. It pairs very well with the Pentax TC on a K3, but I would never use the Pentax TC on my K1, the vignetting coupled with the extreme edge distortion leading into the vignetting is just not good enough to be classified as useable on FF. AF is significantly better; faster more accurate. (Anecdote: My 150-450 had issues with its zoom and is now in repair. When I asked my GF, the main user if she wanted the lens repaired or to get another option, she was adamant that I get another 150-450. She did NOT want to "downgrade" to another 150-500.) I personally use MY ultimate long lens, the Sigma 500 f4.5 and the Pentax DFA gives it a pretty good run for its money. The Sigma is slightly faster at focusing for BIF and pixel peeping sharper for objects beyond about 50 yards. Inside 50 yards I have a tough time telling the difference, and that's probably the extra 50mm the Sigma has. The Sigma 500 f4.5 is a 5k lens. Bottom line, I tried to go cheap and budget in so many different ways, and nothing really worked to my standards or expectations. When it comes to long FL lenses, you better be prepared to ante up, because you can't take shortcuts and expect the same results. PS - the 120-400 is trash...

Thanks sharing your experience , especially regarding the difference between the sigma 50-500 and 150-500. Regarding the use of TC on the DFA70-200, and K1, I tried and it works very well, AF is fast and accurate. The question is how much focal length needed on full frame. So, far, for what I'm doing the 70-200+TC and 150-450 overlap and 450mm is too short on full frame. I'm considering keeping the 70-200+TC (100-300) and eventually selling the DFA150450 to finance a 560 f5.6 or 500 f4 sigma in Nikon mount. I look forward at what may be available next year from Pentax if they offer an upgrade of the DA560. The reason is, for wildlife, the 150450 is too short on FF, even in the best conditions, and for safari kind of shooting, the 100-300 range is good enough. The choice of focal length belongs to use cases. My opinion is that the 100-400/500 ranges are kinda suited to apsc era for wildlife, and full frame use for wildlife require FL in the range between 500mm and 800mm. Otherwise you just crop your 400mm/500mm and in this case the non full frame TC is non issue. Usually, the zooms such as 100-400 , 150-500, 150-450 are on the experience path before upgrading to a longer prime (that's why those sigma zooms are so many on sale second hand on ebay, usually, when you start getting into long lenses, you get the cheap ones , make up your experience with it to figure what you need and then sell it and buy a long prime), when money allows. So, that all depends where we are in our experience path.

---------- Post added 31-10-16 at 07:34 ----------

I find that camera / lens settings are very important in getting the best photograph with any large, heavy super telephoto lens. Proper F stop, shutter speed, ISO, support method used, etc. are all critical.

Exactly, straight to the point. I'd add that vibration is the next issue with long lenses. Get closer to your subject (if you can) and the MTF chart is irrelevant. Most lenses are capable of stunning photographs when framing the subject to match the size of the sensor.

[redpit]

I have both the Bigma 50-500 (which is better than the 150-500) and the DFA. I have written many times my opinion. The DFA is a clear winner between the two in almost every aspect (except the focal length range of course where the Bigma is the most useful lens existing out there and the weight). I suggest you get the DFA (it is usable with the TC too and still accurately autofocuses) but if money is a big problem you can get the Bigma and it is a very good lens and much easier to handle and get results than the DFA.

[planteater]

I have the Sigma 150-500.............. When it is used, I recommend the lens OS to be set to off, camera body SR on, using "Continuous" AF mode, and "Spot" AF focusing area mode.

I'd second this. After extensive testing with my K30 I decided there wasn't much to choose between the In-body or In-lens stabilisation. On my K70 the In-body wins hands down and it's going to be the same for other newer bodies. I'd also recommend hi-speed shooting as any stabilisation system seems to be a bit 'statistical' - the micro-movements in the IBIS system are inconsistent and pictures taken a fractions of a second apart vary widely in sharpness.

I probably will upgrade to the 150-450 as the IQ is definetly there as well as the weatherproofing. Every time I reach for the credit card though I see reports of unreliability and cumbersome handling............. just can't get past that at the moment.

[Des]

But I need more zoom.

Maybe you mean more reach. Don't rule out a prime. The DA*300 f4 and DA 1.4x TC combination offers a lot of bang for buck. And you could use the TC on the 70-200 as well. With that combination you would be covered for 70-200mm f2.8, 100-280mm f4, 300mm f4, and 420mm f5.6, for much less than the 150-450.

[HopelessTogger]

Thanks everyone.

Decision: It's going to be the D-FA 150-450, but only once the zoom reliability issue is confirmed to have been solved.