If you're reading this post, I’m going to assume that you are at least somewhat serious about photography. You are the person who has progressed past using a cell phone camera or point-and-shoot and are ready to challenge yourself. You will end up wanting to buy a DSLR or at least something with manual controls and interchangeable lenses, like a mirrorless camera.
Try many different cameras -- you'll soon notice what you like and what you don't like.
What are the factors you should consider when choosing your next camera? Here they are in no particular order:
In years past, the megapixel number was the most important thing to look at. The number of pixels determined how big you could print an image while maintaining a clear, non-pixelated image. Nowadays, you won’t find many DSLRs under 10 megapixels (big enough to print poster sizes), so it isn’t much of an issue.
The thing to look for now is the sensor size. The sensor size determines the quality of the pixels. 10 million pixels on a small sensor looks different than 10 million on a large sensor. There are many different size sensors out there and they generally get more expensive as they get bigger. See the chart of common sized sensors below.
Different sensor Sizes
2. Lens options
Let’s be honest, there are two camera manufacturers that are making the majority of the equipment out there and have the majority of the resources to devote to updates: Canon and Nikon. They have more lens options than any other company, more used lenses on the market, more support from other consumers, and a better chance of being in business when you are ready to upgrade.
Buying a camera is investing in a system, and once you’ve invested $100 or $100,000 in a particular manufacturer's lenses, you will be less likely to want to change systems. There are few other companies with a good selection of lenses. Just make sure you do your homework on what is available before you buy into a system.
3. Interface and configuration
Take note of how quickly you can move through the menus of a particular camera and how intuitive the buttons are to use. You want to find a DSLR body that's easy and fast to use. It should be something that is intuitive and comfortable. If the technology is clunky or the important functions take too many steps to access, keep looking.
4. Size and weight
Take some time to evaluate what you are willing to carry around with you. You may want an expensive and full-featured DSLR, but if it’s so heavy that you are unwilling to carry it, a more stripped-down version may be more suitable.
5. Build quality
Ask yourself what kind of build quality is necessary for the type of work you wish to do. Camera bodies are usually made of plastic, metal or some type of alloy. The tougher the conditions and more extreme temperatures you find yourself shooting in, the more rigid a body you would want. Weatherproofing is also important for people that are shooting in dusty areas or wet climates. More expensive cameras are able to withstand more of the elements before it affects picture quality.
6. Other considerations
Budget is usually the largest factor in a DSLR purchase, as they can range from $500 to around $7000. When making a budget, keep in mind that you also need to purchase memory cards and perhaps an extra battery, external flash and a bag.
The burst speed and maximum shutter speed are important for some photographers, like people capturing sports or wildlife.
Low light performance and maximum ISO speed may be important if you cover events or in dim situations without a flash.
Lastly, make sure the LCD display size is large enough that you can see what you are photographing and get a good idea if the subject is in focus.