The Sony A1 is now sitting on my desk beginning its testing. In terms of my own photography, the natural places to test the A1 in extremis are with landscape photography and in wildlife/sports work. Which led me to contemplating the lenses I needed to pull out of the gear closet to put on the A1.
If you're not familiar with Phillip Reeve's list of Sony FE lenses, you probably should go check that out (you can also explore the Sony and Third Party lens lists on this site, though that will resort in you doing a little manual work to consolidate what's available). The total FE autofocus lens list right now is approaching 100 lenses.
For landscape testing, there are a plethora of great lens choices. I tend to use 24mm or wider for landscape work, and if I include the two Zeiss 25mm lenses, I've got 38 choices. The problem happens at the other end of the focal range, where I'm looking at lenses for wildlife and sports work. Above 100mm, we have exactly eight autofocus lenses. It's probably worth listing them:
- 100-400mm f/5-6.3 Sigma
- 100-400mm f/4.5-5.6 Sony
- 135mm f/1.8 Sony
- 135mm f/1.8 Sigma
- 135mm f/2.8 Zeiss
- 200-600mm f/5.6-6.3 Sony
- 400mm f/2.8 Sony
- 600mm f/4 Sony
The last two of those list for US$12,000 or more, so aren't in my gear closet. The 135mm primes aren't flexible enough for my testing. That left me with the 100-400mm and 200-600mm choices. Yes, we've also got possible 70-180mm, 70-200mm, and 70-300mm choices, but those probably aren't going to push my testing enough to see what the camera can really do.
But this does introduce the problem that the Big Three all have in differing degrees: the mirrorless systems "aren't all there yet." Canon's missing the top body and a slew of native lenses*, Nikon's missing the top body and a slew of native lenses*, and Sony's still missing some lenses that would make them fully competitive, though they do now have a top body.
* Both Canon and Nikon have DSLR lenses that work just fine on their mirrorless bodies, but those are not optimized lenses for the system, and the double mount introduces potential other issues.
It's pre-mature to conclude that any full frame mirrorless option is fully fleshed out, though Sony does indeed come the closest. They should, given their long head start.
My guess is that Canon will now be pedal-to-the-floor and will get to "complete" right behind Sony, with Nikon not quite matching that, but within shouting distance. I don't think the L-mount cameras will get there, as about the only lens maker that could fill in some needed exotics is Sigma, and none of the L-mount systems really have the AF systems necessary to take full advantage of them.