Help with lens focal length and angle of view

[FlexiPack 0]

I need a fairly wide angle of view to cover the back door and garden. To help me work it out I took a photo on my DSLR (Canon crop 1.6X sensor) at 10mm, this covers what i need. Probably 11mm would but 12mm doesn't. According to a field of view calculator, this gives me a 106 degrees diagonal field of view.

 

The field of view figures that are quoted on CCTV camera specs, are they diagonal? If this is the case, am I right in thinking that a 1/3" sensor with 2.8mm will give me roughly the same 106 degress angle of view?

[StefanB 0]

Have a look here or here.