These are my personal recollections and experiences. I'm an American living in California. Always check before you buy if the specifics are important to you. These change with time and dealer and vary greatly by location.
A reader wrote that he was having a problem returning a non-defective lens that he just didn't like. He had a problem because he had already filled out the warranty card. He had to do that because the maker demanded the card be returned within 10 days. The dealer wouldn't take it back once the card was gone or filled in.
How can you enjoy a 14 to 30 day return policy if you have to register the warranty sooner? I get to the solutions further down.
Dealers won't take convenience returns after you've written on registration cards or thrown away the box.
Returns and Return Policies
I buy online because the places I use (usually Amazon and Adorama) take things back for full cash refunds if I just don't like it. Retail camera stores usually won't take something back just because you didn't like it. Costco and Ritz are exceptions at retail. They take almost anything back.
Return policies are very specific and vary by dealer. You need to return everything exactly as it left the store. Write on the warranty cards or lose the packing material and you're out of luck.
Dealers differ on what they do with returned products. Some dealers send everything back to the manufacturer, who retests it, marks it as REFURBISHED, and then has to sell it at a loss. In this case your arbitrary return is costing someone a lot of money.
Other dealers put it back on the shelf for sale to the next customer. Fry's is awful: a lot of the stuff in their store has stickers telling you it's a used product someone returned, but don't offer you much discount. When I've returned stuff they taped it up and I presume threw it back on the shelf without even looking inside. I've had to buy things at Fry's and couldn't find new product: all those on the shelf were used!
There's no cost to the dealer when you return a product that was already open box when you bought it.
Resales sound shifty, but I'd much prefer to buy from a place with a fluid return policy. Why? I check everything I buy. Even if someone returned something with some weird hidden damage I could return it and get a good one. I'd never buy something I couldn't return, or at least try first. Camera stores get very few returns, so I just don't worry about it. I've never bought anything, except at Fry's, which seemed like someone else had used it. Even products I've bought marked "Refurbished" from Bose and M&K Sound have always seemed brand new. I don't know which, if any stores other than Fry's, puts returns back on the shelf for sale.
Save the Boxes!
I've always had good luck because I save everything. I have boxes for lenses I bought back in the 1970s! I may be nuts, but you do need to save your boxes until after your return privilege expires. If you chuck your boxes you chuck your return privilege.
Normal people buy a TV and throw away the box immediately. When a friend had a new stereo die after a week they had to ship it out and wait for warranty repair, instead of being able to swap it for a brand new one at the store.
Having the boxes is also critical to an easy resale if you upgrade, so save them anyway. One of my pals is a clean freak, so he sells his boxes for cash instead of tossing them. People buy them to resell with otherwise unboxed used lenses. If you're buying, be sure the serial numbers on the box match those on the product.
Dealers are offering you a service at their expense by accepting returns. They don't ask much on your part, and do require you return everything the way you got it.
Defects that Aren't
I often hear people thinking they have a defective product. Over 9 times out of 10 it's the owner using it incorrectly. 99% of people who think something is unsharp aren't using their lens correctly, misunderstand depth-of-field, can't hold their camera still or aren't familiar with the effects of Bayer interpolation.
Of course I'm both picky and experienced in testing all this stuff. Most people lack the experience to know what optical defects represent today's state-of-the-art. These folks start testing, they find defects which are simply the limits of modern technology, and return things unnecessarily. It's exactly like the phoney wine snob who sends back three open bottles of wine thinking he's impressing the others at a restaurant. Those guys are restaurateurs' worst nightmare. Restaurants of course courteously keep bringing out new bottles, but they now have to drink those bottles of perfectly fine wine themselves.
Even manufacturers can be wrong: my Epson 1200 printer of 1999 made a hissing noise when idling. I called Epson and asked if this was normal. They said it was a defect and sent me a replacement the very next day. It did the same thing. I called again, and a more senior guy pointed out that no, they all did that, and apologized for any trouble I may have been caused by yesterdays' guy. No trouble to me, but Epson just bought themselves a used printer due to a lack of information with one of their reps.
I had one reader have Nikon take his D70 back for hot pixels when in fact the images I saw were simply star trails! Nikon presumed they were hot pixels, even though the only happened in the sky at twilight and were all diagonal line segments rotating around a common center.SOLUTIONS
I never fill out my registration cards until after the exchange period expires.
Today you can register almost anything online, and never have to write on the cards. Register to your heart's content.
In the old days I would make photocopies of the registration cards, and mail in the copies.
In every case I keep the registration cards clean and blank. I'm a weirdo: I save everything. You ought to see my cars with all their original dealer hang tags and documentation!
I live in California, USA. Your state and country will vary. I'm not a lawyer; this is what I've heard. If it means a lot to you I suggest you investigate with your state's department of consumer affairs. They are very familiar with these issues.
When bringing in gear for warranty work Nikon's counter people have told me that I'm fine for the extended warranties (5 years on lenses) so long as I have all the original receipts and paperwork. I was told registration only makes a difference if I've lost the receipts.
Also as I recall, in the USA it's a legal requirement on manufacturers to honor warranties without requiring registration. This isn't Germany in the 1930s.
Check locally, and as I understand it, even if a manufacturer claims it's mandatory, it probably isn't so long as you retain proof of new purchase from an authorized dealer.
Authorized vs. Unauthorized Dealers
Not all stores that sell cameras are authorized dealers. Every store has to earn the right to sell any given product, and signs contracts with each maker if they are authorized.
Canon, Nikon, Pentax, Leica, etc. don't let every store sell their cameras just because they ask. Stores that go out of their way to say bad things about any major camera brand most likely are not an authorized dealer for that brand even if they sell it. Stores sell cameras for which they are not authorized by buying them from another dealer, meaning what you think is a new camera is actually used (by definition) and probably not warranted.
We had a big store here in San Diego that used to bad mouth one of the big brands, and I realized after asking a rep from the camera company that that store, even though they sold that brand, wasn't an authorized dealer. Obviously if a store has to buy one brand from another store they make a lot less money. They would rather sell the brand they get directly from the maker.
No major camera brand has any of the problems that some camera store salespeople invent, like inferior lenses or rampant reliability issues. By major brand I mean first-rates brands that compete among themselves like Canon, Nikon, Pentax, Olympus, Leica, Mamiya, Panasonic, Sony, Epson, Minolta, Zeiss, Hasselblad, Rollei, and Linhof. I'm not a fan of discount, non-camera brands like Sigma, but that's just me. If a store claims any of the major brands puts out inferior products in an attempt to sell you something competitive, ignore them and buy elsewhere. I usually shoot Nikon, but that's just me. All the other major brands are equivalent.
Unauthorized Dealers and eBay
I used to work as a sales manager for an equipment manufacturer. We were very, very clear: when you buy from an unauthorized source, even a legitimate (but unauthorized) dealer selling unused equipment in sealed, unopened boxes with blank warranty cards, you are buying, by legal definition, used equipment. Our warranty only applied to the original purchaser. We offered no warranty on used equipment, which included equipment bought from bona-fide but unauthorized dealers. In actual practice we usually honored the warranties anyway, but be warned: buy from unauthorized dealers and on eBay and you're almost always buying used, unwarranted equipment regardless of the claims of the seller.
Buying from an unauthorized dealer is the same as buying from a stranger. Having a receipt from an unauthorized store is as helpful in getting warranty service as having a receipt from your mother. It's a nice thought, but doesn't guarantee you'll have any valid warranty.
Individuals selling on eBay, even if they seem to make a business of it, aren't authorized dealers. Some dealers do sell on eBay, but I know of no individual people who are. No one is authorized unless the camera maker concurs. If you wonder, call the camera company and ask if any seller is an authorized dealer. Most of what you get from people on eBay is used, even if they claim it's new. Buy one of my 20-year old lenses and it looks new, it's in the box with blank warranty cards, packing material and those little "Do Not Eat" bags of silica gel, but it's certainly not covered by factory warranty because I'm not a dealer.
If you engage in the shady practice of buying from the bottom feeders who buy hard-to-get camera gear on speculation of selling it back to you at a higher price (like 18 - 200 VR lenses today), even if they give you their original receipt you may or may not be able to get Nikon to fix it for you. Nikon isn't obligated, since you're not the original purchaser. Read the warranty papers for details.
How do You Tell if a Dealer is Authorized?
Call the manufacturer and ask.
USA and Gray Market
I explain the differences here. In a nutshell, gray market products have no warranty except whatever promises the camera store may offer you to repair things itself.
Most camera makers will do you the favor of honoring warrantees in the USA for cameras bought while traveling, even though those cameras carry no warranty for the USA. They usually require you to have a detailed receipt showing you actually bought it while overseas.
Buying from overseas by phone, mail or internet doesn't count. You have to have bought it personally while traveling.
Mamiya is especially weird about this. They do a very good job impeding American's abilities to buy Mamiya products from outside the USA.
These are generalizations. Always check with a cameras's maker in your local for specifics.
In the USA you can get the current warranty information from Nikon at (800) NIKON-US or (800) NIKON-UX for digital products.
If you find this as helpful as a book you might have had to buy or a workshop you may have had to take, feel free to help me write more with a donation. Thanks! Ken.