300 mm correspond to 600 mm on FF, the same maximum focal length Nikon and Canon offer. Needless to say that the Olympus lens is a lot, lot cheaper than either of the 600 mm cannons. And faster.
(Note: I'm using a Nikon.)
Yes, but my 400/2.8 on an APS-C body is the same 600mm field of view and I can add a 1.4x or 1.7x teleconverter (I'm not a fan of the 2x TC) and get acceptable pictures at longer ranges (840/4 and 1020/5.6.) Olympus only offers a 1.4x TC, so I'm dropping an additional $7200 to go past 840mm on the Olympus system to get the Sigma 300-800/5.6.
I have two more longer primes, 500mm and 600mm to choose from with Nikon or Canon. The 500/4 gives me 750/4, 1050/5.6 and 1275/8 equiv., and the 600/4 gives me a 900/4, and 1260/5.6 equivalent-- so actually if you're going to compare apples to apples, both Nikon and Canon offer more range on their
crop factor bodies with their lenses. (I'm pretty sure I'd have stability issues with the 600 plus the 1.7x, so I'm omitting it from the comparison.)
Now throw in the fact that I own one and rent either of the other two in most major metro areas for the Nikon and Canon systems and it just simply doesn't make sense for me and my type of shooting. Neither does a view camera- and I've spent a lot more time cleaning dust out of 4x5 and 5x7 film holders. I'm glad 4/3 works for some people, it's a non-starter for me.
The 1200-1700mm was available until 1999 on special order for $75000.
That's about $24,000 less than the price of the Canon 1200mm f/5.6 prime. I've only seen one being used in field conditions. The photographer either had the sales to justify it or the money to spend.
My 400/2.8 AFS-II was an ROI justified purchase. If Sigma ever releases the 300-500/2.8 I'll be knee-deep in spreadsheets.
How about slapping a bigma on one of these and getting a 100-1000 equivalent FOV? Or a sigma 300-800 and getting a 600-1600?
The Bigma is f/6.3 on the long end and while it's a stellar lens for its price, it's not in the same league as the primes from Nikon or Canon and I'd assume Olympus. I own one, and when it was all I had to shoot I made do and missed lots of shots due to the slow speed. It's 1/3rd of a stop slower than the 300-800.