When buying a camera case, there are a number of main points to consider.
First, what is your price range? Cases can vary from under $10 for a cheap, small polyester and nylon case, to over $600 for a fully-loaded, backpack-style, water-resistant case. The price of the camera you’re protecting will undoubtedly affect how much you want to spend on a case — after all, if you’re trying to defend $6000 worth of equipment, investing whatever it takes in a good case is crucial.
Second, what will this camera case be carrying? If all you’re looking for is something to tote your point-and-shoot digital around with, you may want to look at manufacturer cases. These are usually quite affordable, and custom-fit for your specific camera — ensuring maximum protection, and minimum bulk. If you have a SLR camera with body and one or two lenses, and perhaps some extra flash memory (or film), you will probably want to look at a shoulder-strapped case — again, minimum bulk while comfortably carrying your supplies. If you have a number of lenses, extra film or memory, and even a tripod or two, investing in a backpack case is a great option.
Third, how much protection does your case need to offer? The simplest, lightest, and cheapest cases are made from a very simple, stretchable nylon and polyester combination. At the higher-end of the market you find water-resistant, tear-resistant, and very durable nylons. For photographers in extreme conditions, hard camera cases are available — these can be found made from durable plastics, aluminum or titanium. Water proofing can range from absolutely none up to completely waterproof to extreme depths. Internal padding is also well worth examining — a perfect exterior does no good if your camera and lenses are banging against each other inside the camera case. Most large cases have adjustable panels to better fit your components, and some offer custom foam molding to ensure absolutely no movement.
Lastly, how much will you be moving around with this camera case? For small nylon cases, this is a non-issue, but for larger, professional cases it becomes crucial. If you are primarily a studio photographer, and need only to move your equipment from the car to your shoot, weight and carrying are less of an issue. Handle-held, bulky, and metal-formed cases are not entirely out of the question. If you plan on extensive field photography, however, particularly in rough terrain, strapping and weight become a central point of concern. Keep in mind that though neck straps may seem perfectly fine when trying out a case in the store, after six hours hiking with your gear around you neck, you may be deeply regretting passing up a hip-strapped, or backpack-style camera case.
There are a handful of lesser issues you may want to consider when buying a camera case. These include:
Alternate materials — it is possible to still find cases made of leather or natural fibers, though they have largely been replaced by synthetics due to their light weight and durability.
Tripod straps — many high-end cases, particularly of the backpack style, have straps on the side for carrying one or two tripods. These can be a great blessing, particularly on hiking-intensive shoots.
Quick release — the ability to get a camera case off of your body and on the ground and open in a matter of seconds can mean the difference between catching the perfect shot and watching it fly away. Quick release features help ensure you spend as little time as possible getting your camera from its case into your hands.
Locks — some cases include their own padlocks or key locks to protect your gear. In general it is preferable to purchase a higher-quality lock to add to your camera case, if you require this added security.
Rollers — like most modern luggage, some of the larger cases have rollers and pull-handles to help you bring your camera case from one location to another (assuming there are level surfaces, of course).