I have a few suggestions. As a recent e-Bay seller who has been stung by a dishonest buyer, I know what happens (your situation is reversed, of course).
You contact seller and demand refund as item is "substantially not as described." Remember that - it is the key phrase.
Seller refuses to give money back. Check.
You file a complaint with Paypal. Say that the item was essentially not as described. They have a form for you to fill out.
They then FREEZE the seller's account. He can't do squat. This will remain this way for several months.
Paypal will ask you to take the camera to a repair place and verify that it is a) not as described, b) not repairable or c) repairable and how much it would cost. You'll have to do the leg work on this yourself, and get a letter from the camera people. You'll have ten days to do so.
Then Paypal will ask the seller to respond and ask him to refund your money voluntarily. He will refuse.
Then Paypal will tell both parties that they will make a decision in 7 to 14 working days. This takes TWO MONTHS. During this time, the seller's account remains frozen.
Paypal will then decide in your favor, deduct the money from his account, and ask you to Fedex the camera back to him at your expense. You will have to provide a tracking number.
The seller is asked to tell Paypal when they get the camera back. If they refuse to do so, Paypal will wait seven days, check with Fedex themselves, and determine that it has been delivered.
Then Paypal will refund your purchase price plus the shipping you paid initially. They will release the hold on the seller's account. If the seller has a negative balance, they will go after him until he puts money in to make his balance zero.
The seller gives you negative feedback, and you return the favor.
And that's about it. I'm sorry you got stung, but believe me, you will win and he will lose when you complain to Paypal. They do NOT take the seller's word for it, trust me. I got royally jacked by a buyer. In your case, you are in the right, so even more good for you that you will win.
Sorry for all the trouble. The seller is in for a world of hurt, he just doesn't know that yet. When he's been through this experience with Paypal, he will never sell anything again on eBay. I know this because I will never again sell anything on eBay. And I've been a member on eBay since 1996 with a 100% rating. Trust me, you'll win.
Best Regards,
Bill Mattocks
PS - As Paypal will tell you, even if they somehow decide against you, you still have eBay to complain against, and then your credit card company - you have lots of options, you can make this guy's life a living hell for doing what he did to you for the next year or so. But you have to go through Paypal first - or they will refuse to deal with you if someone else is already involved.