The original meaning of "は“ is "emphasize", "bold lininig", which turned to mean "theme", "topic". (*Theme should be emphasized) 私のカメラはあなたのとは違う The theme of this sentece is "私のカメラ" The first は means theme. The second は in あなたのとは is for emphasizing. 「ちがう」「やめる」kind of verbs/adjectives like to have ”は” in advance. I think they want, by their nature , emphasizing before them. ※ あなたの ： your thing, yours, ※ と　： focus point of action -> object for comparison. ※ In 私のカメラとあなたのは違う, the theme/topic is "私のカメラとあなたの"

As I understand it, 私のカメラとあなたのは違う is fine and it expresses the same thing, but the structure of the sentence is a bit different. This, to me, sounds like a more neutral statement, while the other structure emphasizes the comparison between the two objects. は appears in two places in the sentence to indicate the comparison. The double は pattern often appears when showing two things that are unlike one another. 私のカメラはあなたのとは違う When I use the double は pattern, I might use it in sentences like the following: アメリカでは英語やスペイン語を話せる人が多いです、日本ではほとんどのみんなは日本語しか話せません。 "In America, many people speak English and Spanish. In Japan, however, almost everyone can only speak Japanese." This is a bit of a generalizing statement, but it serves to show what I mean by example. The two instances are very different from one another and each being presented using the particle は is kinda like saying "on this side A, but on this side B." Does this make sense? If there is anything that is unclear, please let me know.