It looks like an impressive optic for sure.
Light, portable and doesn't domiate your camera bag with a lump of big glass.
The sharpness looks impressive and the angle of view is expansive, boardering on the (OMG, this is actually a bit too wide to easily compose with).
Without the in camera / post prod corner corrections...this lens has chronic mechanical vignetting in the corners, to the point there are black corners of nothing. Which means that Canon is using software to correct the dodgy optics and we loose data due to the stretching and bending and adding of exposure to the far corners.
The flare and ghosting resitance look amazing. It's sunstars look the best I've seen so far.
I think the zoom range is excellent, covering all of the ultrawide points, but curiously maxing out at 20mm. Surely 21mm would have been a better place to end the long end? If it was 24mm I could have used this as my one and only ultrawide lens, with a 24-70L or 24-105L. But no, I have to get ANOTHER UWL to cover that range. That's pushing up my bag's lens slots and pushing up my bag weight and overall lens collection cost by a substantial amount.
The lens hood looks as pathetic as the EF 11-24mm f4L's hood. The lens hood rubs ont he side walls of the inbuilt pedal hood surround and super wears away the lens body finish. Just look at any S/H EF 11-24mm F4L and you will see what I mean. An unusally poor piece of engineering from Canon. Which is bizarre considering how ecpensive this lens is. It's like Canon ran out of budget and engineering effort with the cap (again).
For some, the Image Stabilliser is an obvous benefit. For me and my landscape work, less so because I need the option to shoot multiple images at differetn exposures to create a final image that captrues the entire dynamic range of a scene. That requires absolutely identical image registration with zero movement between frames. This needs to be scrutinised at 100% pixel peeping. This can't be done with hand held shooting regardless of how good the image stabiliser is. Sure for video work or run and gun / walk about types of shots I'm probably quite useful.
One of the things I've loved about the L EF lenses were their durability vs the reast of the competition and in recent years, Canon have been under-enginering the durability of thier lenses. Has anyone else noticed that the newer "easy to clean" flourine coated front elements are a lot more susceptable to scratching?
I'm not happy about the rear gel filter holder. After 20 years of this type of optic (the Sigma 12-24mm being the first of this type), some one really needs to develop a better filter system than rear gels.
For me, I still prefer the EF 11-24mm L f4 with it's abilty to use a drop in filter via the EF to RF adapter. The lack of reliance on software correction to fix the "no where as bad" corners. The fact that it's a lot heavier and larger is not a problem because in the RF dediated lenses, I would need two lenses to cover a similar focal range. One of hte problems this lens will have with photographers who have / are migrating over from the DSLR cameras is that it is effectively in competition with the legendary EF 11-24mm f4 L. It's a lens that will only stand on it's own to the RF purists. Everyone else will conpare it to the Sigma EF mount 12-24, the Canon EF 11-24 L or other offerings. Each with thier benefits and weaknesses. for some, having the absolutely widest land available, that extra 1mm at the wide end is all that matters. For others, there are other compromises or requirements in play. In this case, small and light might not be the deciding feature for many photographers.
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