Sigma 120-300mm f2.8 OS -VS- Canon 300mm f2.8 primes

So recently I came across a photographer who compared up (in a shop) the new Sigma 120-30mm f2.8 OS against a Canon 300mm f2.8 IS M LII and walked away with the sigma not the canon (even though he had funds for either).

So it came as rather a surprised when, his impression, was that the sigma was only reduced in quality next to the canon both bare and with teleconverters, in the corner sharpness and that centre sharpness was fairly even between the two even wide open. This surprised me, a lot, since canons 300mm L f2.8 has always been a very top rated lens and, whilst I've no illusions against sigma making good glass, a half the price zoom lens would seem to be impossible to beat or equal the prime.

So I'm wondering if any others have compared similar spec 300mm primes against the sigma zoom or can point to any insightful reviews and opinions. I'd really love to think that I could get away with a lens half the price of the amazing canon and still push to a high quality 600mm option with OS.

Way I see it he chose versatility over IQ I highly doubt the sigma will have better IQ over the new or even the older canon 300 2.8

Aye there is that variable to consider, then again I've seen what the canon 70-200mm f2.8 IS M LII can do and know of more than one or two photographers who've sold great primes (135mm L) to fund the purchase of the zoom.

I had a non-OS Sigma 120-300....and sold it to pick up an old Canon 300mm f/2.8 non-IS. Plenty of dust in the old Canon lens as you'd expect, but the glass is perfect, and I'm glad I made the switch. Can't speak for the OS version.

My impression was that if the subject was sitting still, the two were close in IQ, however the Sigma's AF simply couldn't track anything moving....and since I use it a lot at racetracks, it was a problem for me. Sure, some of the shots were very solid, just too many misses, so to speak. I find that carrying a Canon 70-200 f/2.8 MKII, the old Canon 300mm f/2.8 non-IS, and a couple of TC's gives me all I need, and I'm using the same backpack I was using with the Sigma (lightweight hiking bag with an insert), so I'm not feeling like I'm carrying around a bunch of extra weight.

I already had the 70-200 for other purposes, and would want to keep it even if I bought a new Sigma OS, which is part of what's kept me away...I just can't justify having two zoom lenses that similar.

Plenty of discussion about the 120-300mm OS here. Reviews too. Probably start around page 70 or 80.

don't have new 120-300mm f2.8 OS. Only had non OS and canon 300mm f2.8 IS I. Like gocolts for stationary things both very close but for action canon kicked Sigma's butt. Now even on the newer OS version sigma still doesn't have the focus limiter switch from what I understand. If new OS AF is as good as even non IS 300mm f2.8 I will want to get it but for so far I haven't seen any real proof.

I agree a limiter switch would have been nice to have on the Sigma, but it's pretty good with a 2X on, this is a bit of a crop. It is heavy to wave about for BIF though

artyman wrote in post #13547932
I agree a limiter switch would have been nice to have on the Sigma, but it's pretty good with a 2X on, this is a bit of a crop. It is heavy to wave about for BIF though

I use my 300 f2.8 for BiF and the Sigma is just about the same weight so it should also be OK. I'm seriously thinking about getting the Sigma before my next safari. However, I still have doubts about the tracking performance of the AF, so any BiF shots (of smallish birds - BHG or smaller) would be much appreciated.

This is a fairly hefty crop using the Sigma 120-300 and 2X, boy do those blighters fly fast!

Anybody shootings field ports with this new Sigma? It would be real nice not to carry 300mm f2.8 anlong with 70-200mm f2.8. Even without 70-200mm f2.8, if 120-300mm OS can match AF performance of 300mm f2.8, the ability to zoom will be so nice when play comes closer.

bobbyz wrote in post #13548499
Anybody shootings field ports with this new Sigma? It would be real nice not to carry 300mm f2.8 anlong with 70-200mm f2.8. Even without 70-200mm f2.8, if 120-300mm OS can match AF performance of 300mm f2.8, the ability to zoom will be so nice when play comes closer.

I shot sports with the older Sigma 120-300, and I thought it did quite well. AF and image quality wasn't on par with the Canon 300mm f/2.8, but I thought it was similar to the Canon 70-200 f/2.8 IS (in AF speed/accuracy and in image quality). Sorry, I can't give you any insights on the newer version, but I'm positive the shots posted in this thread don't do it any justice. From my experience with the older lens, it certainly has the capability to provide excellent images (if the focus is correct). I recently sold mine because I haven't been shooting enough sports to make it worthwhile to keep around.

Here are some examples of sports shots I took with the older Sigma 120-300:

https://photography-on-the.net …hp?p=13311538&p​ostcount=2
https://photography-on-the.net/forum/showthre​ad.php?t=936480

Ben, I know that good copy of the old non OS can do wonders but if I were to judge I will say out of total 10 copies you will get maybe 1 which is good. Been through tons of posts on FM, here as well as on sports shooters. Main issue with non OS was that AF could track well even on 1 series. I never had any those AF issues with any canon lens. I wish with newer OS model, sigma to have better AF performance.

I've seen quite a few examples of the new os version accurately tracking dogs running towards the shooter as well as drag race action. It performed very well in those applications. I cant list links here as im typing on my phone, internet went out here at work.

bobbyz wrote in post #13548812
Ben, I know that good copy of the old non OS can do wonders but if I were to judge I will say out of total 10 copies you will get maybe 1 which is good. Been through tons of posts on FM, here as well as on sports shooters. Main issue with non OS was that AF could track well even on 1 series. I never had any those AF issues with any canon lens. I wish with newer OS model, sigma to have better AF performance.

Did you mean "AF could not track well even on 1 series."??

Nmura wrote in post #13549026
Did you mean "AF could not track well even on 1 series."??

Yup on the old non OS model. You put camera in AI servo mode (1dmk2 for me) and I couldn't tarck my wife walking slowly towards me. It will catch up after 3-4 frames then miss 3-4 frames and repeat.