I tried put the Sigma EF 17-70 with speedbooster onto R7/R50. If you are willing to sacrifice the corners(32>27~28MP for R7, 24>20MP for R50/100/10/50V) or shoot in 1:1 ratio instead. It's feasible.
The 18-50 f/2.8 weighs 300 g while the 10-18 f/2,8 weighs 270 g. I own both and they are both excellent. Update: perhaps you should be comparing the 18-35 Sigma with the 28-70 f/2 Canon.
Correct me if I'm wrong, but aren't speed boosters used to keep the same effective FOV and f/ratio when adapting FF lenses to crop bodies? The Sigma 17-70 is already a crop lens. Maybe that's what's killing your corners.
Why use the speedbooster and not the normal RF to EF adapter? the 17-70 is already a crop lens and works perfectly corner to corner on RF aps cameras...
It's not limited to FF lenses, I want the lens "faster" and wider
Just experimenting. I have 18-50 now for the standard zoom purposes, 17-70 becomes redundant so I tried to make use of it.
I completely forgot about the sigma 18-50. I try not to talk about lenses I haven’t owned or at least handled, but that doesn’t mean I should forget to mention them. The 18-50 is light and goes great with aps-c, but it’s FF comparison isn’t a 28-70 f2 or 2.8, but I guess in EF the 24-70 f4, which is much heavier, still faster (f 4.5 is the FF equivalent) much wider on the low end and a little less telephoto on the long end. Or the 24-100 4/7.1, wider and faster on the low end, longer and much slower on the long end, 95g more. I’d think the 18-50 wins on size and matchups enough that I’d much prefer it to any other standard zoom on rf-s. I use three formats a lot, and I feel like even I forget that the lenses are slower on APS-C, and also forget that I can get good or great subject isolation with an f3.5 or f4 lens on full frame, just need more intentional planning and sometimes the full frame solution is lighter. I much prefer the Sigma 56 f1.4 to the RF 85/2, even if the RF is a little faster, because the combination is so much more compact. The Sigma was even better than the of EF 85 1.8, a small and light lens, because that lens benefitted from being stopped down. I am willing to bet that if Canon does release a 70-150 2.8, it will be much lighter than the sigma 50-100 was/is, for the same speed and probably IQ.
That's fine if that helps your creative process. But you can't blame the Sigma lens for degradation in the corners because the booster is compressing an image circle that doesn't go all the way there.
50-200 2.8 and we have a deal.
