How to choose a digital camera

BLUF (bottom line up front)

If you are looking to move beyond your smartphone camera, you should choose a DSLR or mirrorless camera for the ultimate quality. For a more modest price and for a smaller, lighter, more convenient system that gives full creative control, consider a superzoom.


Digital cameras mostly fall into a few broad categories:

Picking among the above is your most important decision. But before getting into the trade-offs between these categories of cameras, let's briefly discuss what determines the quality of the images you shoot. The quality and composition of a digital camera is mainly defined by four quantities: resolution, lens aperture, lens focal length / zoom range, lens quality, sensor sensitivity, and camera software.


Nearly all digital cameras use CMOS or CCDs as the sensing element. This is what takes the place of film. The resolution is the number of pixels in the captured image. Computer images are divided into little dots called pixels. The more pixels, the more detailed the image can be.

Today, a camera's resolution is that last thing you should be worried about. Virtually all digital cameras have resolutions of more than 10 Megapixels. With such resolution, your image detail will only be limited by sensor resolution if you have everything else about your shot absolutely perfect: a great lens, held very steady, precisely focused, on a subject that is stationary. So do not make camera resolution a decision point in your camera selection.


Lens aperture

The aperture of a lens is its maximum opening. The bigger the aperture, the more light is gathered, and the less light you need to take a good photo. This is the most overlooked lens specification, but it very important, especially if you like to take photos indoors without flash or from a reasonable distance.

Lens aperture is measured in f/numbers, such as f/2.0 or f/3.5. An aperture of f/2.0 literally means that the lens opening is half the focal length f of the lens. Thus, smaller numbers mean bigger lens openings. You would rather have a lens that is f/2.0 than a lens that is f/4.0.

I really like to have a fast (large aperture) lens. It means I can shoot photos indoors without flash, and these look a lot more natural than flash photos. You can also take a lot of photos less obtrusively without a flash. Digital photographers tend to shoot a lot of photos, and you can drive people nuts if you shoot 20 flash photos in ten minutes. They will hardly notice your shooting these twenty shots with flash disabled, and you will get much better candids.

A large aperture lens also gives you the option of having a shallow depth of field. Depth of field is the range of distances for which objects are in reasonable focus. Sometimes you want everything in focus, but sometimes you would like a shallow depth of field to separate the (sharp) subject from the (blurry) background. A large aperture lens gives you that option.

Lens focal length or zoom range

A zoom lens has a variable focal length. The focal length determines the magnification of the lens. A short focal length is a wide-angle lens, great for taking in large vistas. A long focal length is a telephoto lens, allowing you to get a tight photo of a distant object or person. A zoom lens lets you combine both of these and everything in between into a single adjustable lens. If a camera has a 3X, zoom, it means that the longest focal length is 3 times the shortest.

In the subsequent discussion I am using 35-mm equivalent focal lengths.

Many digital cameras have a 3X zoom, with a focal length range from around 35 mm to 105 mm. Some have a much wider range. 35 mm is a modest wide angle, and 105 mm is a modest telephoto. A few cameras have extreme zoom ranges of 8X, 10X, or even more. These generally have a minimum focal length of around 25mm, but these usually have a much longer maximum focal length.

Long focal lengths mean you can get a tight photo of your children's faces, or a shot on the soccer field where you child is actually recognizable. Extreme focal lengths let you get in real close to the action even from the sidelines of a soccer field.

(Important: ignore "digital zoom" specifications in ads. Only pay attention to optical zoom. Digital zoom is of no value. All it does is crop the image in the camera. You can always crop an image in software after you have transferred it to your computer.)

Long focal lengths present challenges for photographers. It is hard to hold a camera sufficiently stable at a focal length of 300 mm. Bright sunlight helps, and a tripod or monopod can do wonders. Better cameras have a stabilized lens, that compensates for camera shake. Good stabilization can make a remarkable difference in sharpness of handheld shots at extreme focal lengths.

Lens quality

Lenses with the same focal length and aperture can differ substantially in quality. A poor lens is not as sharp, and it may exhibit chromatic aberration, which means that all colors are not brought to the same focus. This usually shows up as colored fringes at high contrast edges.

Unlike aperture and zoom range, you cannot read the lens quality from typical specifications. The two best approaches to getting a good lens are (1) read reviews, and (2) stick with reputable companies.

Sensor sensitivity

In low light conditions, nothing affects image quality more than the sensitivity of the sensor. With low light, images can be noisy. The most important determinant of the noise in a sensor is the size of individual pixels. So for lower noise, you want a big sensor and fewer pixels! Cramming tens of Megapixels into tiny sensors means very tiny pixels, which in turn means noisy images in low light.

In-camera Software

Here I am not talking about photo software that comes with your computer, but rather the software built into the camera. Taking a digital photo means a fair amount of computation. When you snap a digital photo, the camera first grabs a "pre-photo" to determine the brightness and color balance of the scene. It then shoots the real picture, based on the earlier information.

This is an important calculation. The importance of brightness is obvious. Less obvious is how radically the colors of different light sources are. Slide photographers know this. If you shoot standard "daylight" film indoors under incandescent lights, everything is orange. Film photographers see less of a problem, because the processing labs that print our photos correct for most of these color shifts. With digital photography, you want the camera to do all of this color compensation for you. This is not easy, since the camera needs to distinguish between incandescent illumination and a daylight scene with a lot of red and orange colors.

Image format: JPG and RAW

If you are reading this page, you are likely serious about getting the most from your photos. If so, be sure to get a camera that support RAW file types, as well as JPG. JPG's are fine for point-and-shoot images, but if you wish to tweak your images at all, RAW gives you much more potential. Much of the shadow and highlight details of your photos are discarded with saving as JPG. RAW retains this information.

Media type

Most digital cameras use Compact Flash or Secure Digital. The difference is not worth worrying about unless you already have a good supply of one type.

Be sure to pay attention to the recommended speed class of cards. If you are shooting video or shooting stills in rapid succession in RAW, this can be important.

Camera types

With all that background, how do I choose a camera?

Point and shoot

Point and shoot cameras are a dying breed, simply because smartphone cameras are now so good. But there continue to be fans, if for no other reason than preserving the battery on your smartphone during days with lots of shooting. But if you are serious about photography, you want more: more range of focal lengths, more low light capability, more ability to manipulate images after the fact. That takes to the following categories:

Interchangeable lens cameras

For the very best quality images, you need the very best lenses. That means using a camera that lets you pick the best lens for each occasion.

The very, very best images are from fixed focal length lenses. So a photographer might have a short focal length lens for wide-angle shots, a long focal length lens for telephoto images, and something in between. You can also buy zoom lenses, and many photographers will carry one lens that goes from extreme wide angle to mid-range, and another from mid-range to telephoto. These tend to be better quality than a single zoom lens that spans the entire range of focal lengths of interest.

In the days of film, it was the invention of the single-lens reflex (SLR) camera that resulted in interchangeable lens cameras taking over serious photography. With these camera, a 45 degree mirror behind the lens reflects the light up onto a ground glass surface that the photographer views through the viewfinder. (For the technically minded, the light undergoes reflection and magnification along the way from ground glass to eye.) With this, the eye sees what the sensor will see. When taking a photo, the mirror flips out of the way, allowing the light to fall on the sensor instead of the ground glass.

Digital SLRs (DSLRs) simply replace film with an electronic sensor.

Until recent years, getting the best quality camera meant getting a DSLR. However, as sensor resolutions and digital displays improved, we see mirrorless camers competing with DSLRs for the attention of serious photographers. In these, there is no mirror or ground glass, as in SLRs. Instead, the signal from the sensor is fed to a display, either on the back of the camera or enclosed for viewing through a viewfinder. The advantages are that the cameras can be smaller and lighter, since no room need be reserved for the mirror assembly. They are also quieter, silent if you choose, since there is no mirror to slap out of the way. (The clack-clack-clack you hear at press conferences are the mirrors on SLRs of the press corps).

My sense is that the very best cameras are still DSLRs, but mirrorless interchangeable lens cameras are closing the gap.

If you choose an interchangeable lens camera, after deciding between DSLR and mirrorless, your next decision is sensor size. "Full frame" cameras are so named because they have a sensor the same size as 35mm film. Next smaller are APS-C and then "micro 4/3's". Bigger sensors mean less noise, but also cameras that are bigger and heavier.

Bear in mind that having an interchangeable lens camera likely means you will end up spending more money in the long run on lenses than you spent on the camera body.

One of the most important attribute of nearly all such cameras is the degree of control they allow the photographer. They will have a "program" mode, that sets aperture and shutter speed for you, aperture priority (you set the aperture and the camera chooses the shutter speed), shutter priority (you pick the shutter speed, and the camera chooses the aperture), and completely manual, where you set everything yourself. ISO (light sensitivity) may be automatic or manual, depending on mode. Such modes give great creative contorl to the photographer.

All-in-one and superzooms.

These cameras are designed on the very same principles as the above "mirrorless" cameras. The difference is that a zoom lens is permanently attached to the camera. All-in-one cameras typically have a zoom range of 3x or 4x, perhaps 35mm to 105mm (35 mm equivalent). Superzooms have wider zoom ratios, perhaps 16x or 20x, for example 25 mm to 400 mm (35 mm equivalent).

Most such cameras have the same choice of control (program, aperture priority, shutter priority, and manual) as the interchangeable lens cameras.

Sensor size of such cameras are typically not as large as interchangeable lens cameras, so low light performance is inferior.

What these cameras, especially the superzooms, is nearly all the control of the interchangeable lens cameras, in a single, relatively light, affordable package. No need to carry a bag with multiple lenses. No need to worry about swapping lenses in a dust storm. They sacrifice the ultimate quality, but they give pretty good quality, a wide range of focal lengths, all in a convenient and relatively inexpensive package.

For many, including me, this is the optimal trade-off.

For those just venturing into serious photography, these cameras will allow you to learn everything there is about technical and artistic aspects of photography. If you "outgrow" this camera and want the ultimate in quality, you will be sufficiently well enough educated that you can choose the interchangeable lens system that is right for you.,

Where do I go to compare cameras?

Steve's Digicams groups cameras according to the above classification system and links to great reviews on each camera. Once you zero in a a few models, you should also visit DPReview.

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