If you know me (or other Tibetan Mastiff people), sooner or later you will see photos of the gigantic TMs. There are Leonberger and Caucasian Ovcharka versions out there too.
While I know for certain that some of the Tibetan Mastiffs photos have been altered (I have seen multiple versions). I can't say the same for the Leo or CO. But I can tell you that perspective has a lot to do with making big dogs look even bigger.
Here are a group of photos I took yesterday with Nobu and Hubba.
No photo editing has occurred. She didn't suddenly get much larger. The only difference is where Nobu is sitting with respect to Hubba.
Nobu will be one year old on Wednesday. She is a little over 100 lbs and about 27 inches tall.
She's a big dog, but not gigantic.