That's why professional photographers always stipulate in their contracts that they retain the copyright to all images they produce - and why they also never work without a contract.
I do not agree. If my company hires a photographer to photograph my products, he will never own the copyright to the photos, and cannot sell them to a competitor.
Try telling that to tens of thousands of companies who hire photographers for their products.
I was referring to creative photography, such as weddings, portraits, or location assignments, where the images are unique and reflect the talents of the photographer. If the photographer is a working professional and isn't able to retain the rights to the images, then you're paying more for his services.
I think most people would understand that proprietary product photography is a different situation - even though the real working pros will still retain their copyright to the images, and they will simply license them back to the company that hired them on an exclusive basis.
In Canada, it doesn't matter what type of photography it is. The person who commissioned the photo holds the rights unless it's stipulated otherwise in a contract. So yes, the photographer can write up the contract with the intention of maintaining the rights to the image, but an educated consumer won't sign such a paper. Wedding, product, it's all the same.