Yes you will get the same lens factor.
The canon is more because it goes to 22mm  and is a faster lense.

Yes! I forgot to mention that.

JMB, any and all lenses that you can attach to your camera will be 'multiplied by 1.6x' regardless of the manufacturer. It is an industry standard to always publish lens width in 35mm film frame equivalent measure since there are a multitude of different sensor sizes on the market and every sensor need it correction multiplier that is supposedly know to the user of a camera i.e. 1.6x for you, 2x for micro four-thirds users, 1x for us full frame shooters, etc.

For a (mostly) distortionless wide angle images your best bet is to go with the Canon EF-S 10-22mm lens. It's focusing speed and accuracy is superb and it's guaranteed to work on all Canon APS-C cameras in the future as well. The little distortions you will have with wide angle lenses can trivially be corrected in Adobe Lightroom, Adobe Photoshop and DxO Optics Pro with their integrated lens distortion correction databases. The distortions will be mostly invisible unless you're looking for them or you have shot geometric straight lines like a piece of furniture or a building with straight walls.

Stay away from fisheye lenses since they will always distort images heavily and even with correction in software you will either have some distortion left or you will need to crop so heavily that you will lose the angle of view benefit from the fisheye lens and could get better results with a normal ultra-wide lens that keeps lines straight from the start. If 16mm isn't enough then you will need to look at full frame cameras with ~14mm ultra-ultrawide lenses or do Panorama Stiching from multiple overlapping shots after the fact.

I got bitten with some old Sigma lenses I have for my film Canon EOS1000F/N that refuse to work on any of my Canon digital bodies (10D, 5D mark II) because Sigma & the lot have reverse engineered the Canon lens control firmware and not licensed it from Canon so aperture control does not work on my current cameras at all on those old lenses.

Sigma makes optically good quality lenses for sure and their price is lower than Canon branded ones, but I would go to a camera shop with your camera body and try the lens out physically i.e.
- go through the different shooting modes (Auto, Av, Tv, M) to make sure that their lens software version supports your camera model and does not result in lock-ups with Err99 like my 10D does
- try focusing close and far alternating between them to get a grasp of the focusing speed and find out does the focus 'search' back and forth or does it work like the Canon ultrasonic (USM) does i.e. it just whirs for a half second and stops spot on. To my understanding both Sigma and Tamron at least have developed their equivalent to USM focusing for some models of their lenses.
- if possible try focusing on dark areas to see how well the lens is able to operate in normal lighting conditions (lot less light than in a shop with fluorescent lighting) though this also measures how sensitive the cameras focusing points are. Usually the centre focusing point is a so called cross-type one and more sensitive than the rest so you will get best results with the centre point focus activated.

My neighbor bought a camera from Simply Electronics for a great price - haven't used them myself and have considered their website a bit dodgy looking, but he got his Nikon underwater point-n-shoot in a couple of weeks without hassles so I guess they are good. Anyone alse got experiences with them?

Oh, and while you're at it have a good look at one of the Canon external hotshoe flashes and a good diffuser for it.

A proper flash that you can bounce off the ceiling/walls and soften with a diffuser will make a world of difference in inside shots and is a must as a fill light when shooting outside in bright daylight to light up the shadows.

For your camera size I would probably look at the new Canon EX320 flash and skip the EX580II that I have - it's large and heavy even on a 5Dm2 much more on a 650D which is half the size. You might get a good deal on the older EX430 if you don't value the video light that is in the 320 unit (though I probably would want to have the continously illuminating video led available in the 320 since your camera is at least 50% ment for video as well as traditional stills.)

Don't go there!,  Don't even think about it!

Looks good Chris.
Tim

Just for fun I downloaded the image and corrected it for lens distortion and removed the key stoning, and the golden cast...not sure it's better. But the wide angle does give you plenty of room to play with the image.
It's a nice room.

Reiska,

I spoke to couple dealers about incompatibility issues  using sigma or tamron lenses you mentioned.

They said they have been in the trade many years and never heard of this problem with legitimate lenses they have sold.  They have heard it has happend to people who have bought of the Internet and ended up with copies-fakes imported thinking they where buying the real thing.  

Jmb

See how this lens goes.  It's a new world to me never worked with wide lenses before.   Your help and advice has been helpfull thank you.

Thank you to others who have afford advice.



Jmb