I discovered these a few years ago and haven't bought anything else for work in my orchard since. Far and away the most comfortable in Florida summer's heat and humidity of anything I've found. Full cut so they don't bind anywhere in any position. Handy pockets.

I don't know what different types of cloth mean. I've always associated canvas with tarpaulins, sails and the like. I hesitated to buy these pants for a long time thinking they'd be stiff and irritating. They are actually much lighter and software than jeans or other work clothes I've tried but I've been happy with their durability. Actually, I don't remember wearing any out. I've torn them up too badly to mend, dumped paint on them or done something else catastrophic and thrown them away first.

I particularly like that I can keep coming back and getting more of these same pants. I really hate it when I finally find some piece of clothing I like, go back a year or two later to get more, and discover that the manufacturer doesn't make it any more.

EDIT 6/14/2015
I've been buying these same pants for several years. The fabric and fit have been very consistent. The fabric in the ones I received recently is heavier and stiffer than in the past. I've washed them three times now They feel the same so I don't think they're going to get better any time soon.

Also, they pull between my legs and irritate the skin when I squat or sit.  This may also be due to the stiffer fabric but I think there's less room in the seat. (The older pants like this still fit fine so I don't think it's me that's changed.)

The laundry labels on both the old and new pants have the same part number, size and description so I think I did receive what I intended to order. They both say "Made in Mexico" so they were likely made by the same manufacturer. I'm afraid Carhartt may have changed the specs deliberately. Maybe to make them more like jeans to please the people who've said these pants feel too flimsy to be durable. But I like these precisely because they did NOT feel like jeans. I don't know what to try next.