2 lenses combination for 7D

Crop cameras use the "sweet spot" of the lens, providing less distortion and vignetting. I've owned the 15-85, the 24-105, and the 10-22, while also a full frame camera. The 24-105 isn't very exciting on FF, IMHO. It has lots of distortion of vignetting, just like the 15-85 on crop. And 55mm isn't much reach for a travel lens.

I like your suggestion of the 10-22 and 24-105 on the 7D, but I would replace the Canon 10-22 with the Sigma 10-20. IQ is pretty much the same, and the Sigma is $300 cheaper, and comes with a 4 year warranty and a lens hood. On top of those advantages it has much better build quality.

When I think of a  travel lens, I think of a lens that can provide reasonable wide angle, but can also provide a bit of reach. The 24-105 does this nicely on crop, with excellent build quality and handling. When I think of anything wider than 20mm. I think "tripod",and at that point your into UWA territory, so switch the lens anyway.

15mm cannot replace 10mm, but 24 mm can replace 19mm. Just step back a few.

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