I used to work in a photo studio and we'd get to do these all the time.
The passeport photos, residency and the ones for immigration are all different sizes. Any professional photographer in Canada should know what this is about and the differences. If not, you should have detailed spec sheets available.
The studio I used to work at is Magenta Studio Photo. They are in Quebec and Ontario. They have all the needed template. You can walk in there and tell them what you want without bringing the spec and they will know what to do.
Who ever suggested Sears, it is an other option. You can also check out Blacks( i worked there to...Astral for those in Quebec). They will also do it and they are supposed to know what you need.
And as someone pointed out, CIC is very picky about the photos, so if you feel like the requirements are not respected as it is indicated on the specs, please have them redo the photo right away.
Also please fallow all the instruction that are indicated. I can not remember form the top of my head the specific requirements for the immigration ones but for example for the ones for the passeport, it says"do not smile", then do not smile, because if you do and then they get refused (and they will get refused definitely !!), the photographer will not redo them for free, where as if it's his mistake, then he will have to redo them for free.
good luck !