iloveoliver wrote:
...I'm shooting with a Canon 7 d mark Ii
I'll just go with the 18-135 and maybe the 10-22...
You have a number of very good options.
Canon offers two excellent ultrawide zooms:
Canon EF-S 10-18mm f/4.5-5.6 IS STM is one of the smallest and lightest lenses of this type, as well as one of few that has image stabilization and one of the most affordable at under $300. It's a bit plasticky, but it's very capable of making excellent images. Something else that might be nice is that it uses 67mm filters, same as the EF-S 18-135mm. For example, they could share a useful Circular Polarizer. Like many Canon lenses, the lens hood for the 10-18mm is sold separately. I'd highly recommend getting and using it: EW-73C, $23.
Canon EF-S 10-22mm f/3.5-4.5 USM is a bit larger, more robust, and somewhat faster ultrawide lens. It costs a little more than twice as much as Canon's other ultrawide zoom. It's also got excellent image quality, is one of the best ultrawide zooms made by anyone. It's an older design now, doesn't have IS (which may not be all that big a deal on an ultrawide... nowhere near as important as IS is on telephotos). This lens uses 77mm filters and a rather large, but highly recommended EW-83C lens hood ($30).
In addition, there are:
Sigma 10-20mm f/3.5 DC HSM... one of the biggest and heaviest UWA lenses for APS-C cameras, and one of few that has a non-variable aperture... uses 82mm filters and is on sale for about $400.
Tamron 10-24mm f/3.5-4.5 VC Di II... has about the widest range of focal lengths in one lens, also one of the few with image stabilization... uses 77mm filters and costs about $500.
Tokina 12-28mm f/4 AT-X DX... not quite as wide, but a robust lens with a good range of focal lengths and non-variable aperture... fairly hefty and uses 77mm filters... $380.
Tokina 11-20mm f/2.8 AT-X DX... the only lens of this type currently offered with f/2.8 aperture, though this makes it larger and heavier... uses 82mm filters... $470.
There are also:
Sigma 8-16mm f/4.5-5.6 DC HSM.... the widest non-fisheye lens you can buy for APS-C cameras... it has strong wide angle distortion effects... $569.
Sigma 12-24mm f/4 DG HSM "Art"... a high quality, full frame lens.... very large, heavy and expensive at $1600.
Canon EF 11-24mm f/4L... a premium, full frame lens.... huge and ultra expensive at about $2700.
These last three lenses all use convex front elements that preclude using standard filters on them. There are special adapters and oversize filters available for some of them.
Personally, I've got the Tokina 12-24mm f/4 (older model) and the Canon EF-S 10-22mm. Both of those are excellent, but the Canon has the best image quality.
Prices of ultrawide zooms for APS-C cameras have come down significantly in recent years, in large part responding to Canon's introduction of the EF-S 10-18mm... a real bargain. Since then, Sigma and Tokina, in particular, have lowered prices quite a bit. Even Nikon has intro'd a similar budget-friendly 10-20mm Nikkor (their other UWA DX zooms, 10-24mm and 12-24mm Nikkors, are ridiculously expensive).
You can compare any of these lenses side by side at the-digital-picture.com. Bryan thoroughly tests virtually everything Canon-related and has very detailed, useful reviews.