I'd argue that Sigma's 300-600 f/4, and specifically its price point, is one of the reasons Canon does not want to open RF FF AF to 3rd parties.
I do worry that's the case. I like Canon gear at the L tier and I own a bunch of it, but I just don't see myself and a variety of others ever spending $10k+ in today's dollars on a single lens. There are simply other life priorities of equal pleasure and competitive expense.
But do I want a nice, more-or-less sealed 300-600 with constant aperture? Oh yeah. So, I admit, Canon would technically lose my dollars to Sigma. OTOH, they're not getting my dollars for that lens anyhow, but at least they sold the body to me.
Actually well-heeled prosumers are more likely to go for the RF native lens - pro photographers are more sensitive to money and would give Sigma's a long look. That lens is a competitor to a number of big whites.
Interesting. I don't know enough pros personally to make a call, but I do understand business and business decisions.
Myself, I've stuck with the still great yet cheaper EF lenses at this time. But, the truth is that the driving factors are:
- I already had EF lenses when RF came out and I prefer to expand capability rather than replace capability, so there was inertia.
- The initial RF lenses that I tried all sucked when it came to full time manual focus override in servo. Af is great on the R6, but it isn't that great. The one R3 I've seen in the field still gets tricked as well. Plus, some of the lenses seem to shift focus backward when acquiring it suddenly, like when an animal appears suddenly in the frame. A lot of that seems to be fixed now by hearsay on this forum and a few personal trials of a limited nature, but again... inertia.
So cheaper is probably a pleasant coincidence more than anything else. And that really depends on the lens: some RF lenses are quite competitively priced with their EF counterparts.
I'm happy to sacrifice some aperture, critical sharpness, edge-to-edge matching sharpness, weight, or wall-to-wall sealing for 1/2 to 2/3rds the price. I don't know if I'd ultimately go with a Sigma 300-600 f/4 vs Canon's, but for the price I'd sure as heck borrow one to find out.
I'd love to see Canon or third parties recreate the spirit of the EF 300mm f/4 IS and EF 400mm f/5.6 in the modern era. Something like a silver-ring set of 300mm, 400mm, 500mm f/5.6 primes to go with the 200-800 in terms of sealing, sharpness, quality, and cost — as an example, pencil in other wishes as appropriate. If Canon does this and excludes Sigma, fine. If Canon cannot get around to it, then I'm happy for Sigma (or Fred, or Sally, or...) do something similar.
I know, I know... all beaten to death. Just daydreaming while waiting for a process to finish...
Yeah, me neither
My whisky is tipped in your direction