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Digital Camera Fundamentals

When comparing the specifications of digital cameras, it can get a little confusing if you are not well versed in the terminology used. As you go through this section, be sure to refer to our Glossary as necessary for clear explanations of terms. In the following paragraphs we explain the most important attributes of a digital camera and what they can offer you.

Categories of Photographers
There are basically four categories a photographer can fall into: Point-and-Shoot (P&S), Beginner, Serious and Advanced.

The P&S crowd is most people who buy a camera to take snapshots of family and friends. They want their cameras to be as easy to use as possible, with minimum fussing over controls, hence the term "Point and shoot." Most digital cameras are therefore P&S types. They provide AUTO shooting mode, and perhaps also Programmed Auto (also referred to as Programmed AE) and Scene Modes.

In AUTO shooting mode, the camera makes practically all the exposure decision for you.

In Programmed AE shooting mode, the camera still makes most of the decisions, but allows you to specify certain exposure parameters, such as ISO, White Balance and which type of flash to use. You can leave everything as default and then Programmed AE is the same as AUTO mode.

Scene Modes automate some of the more challenging shooting situations where AUTO and Programmed AE modes will give you a correct exposure but the picture still does not seem right to us because the camera got "fooled" by the particular lighting in these situations. Some examples are sunsets (shooting into the sun), bright snow scenes (surrounding is too bright), shots by candlelight (surrounding is too dim), night portraits (near subject is too dim, far background is too dim), etc. Each of these situations require an experienced photographer who can manually adjust exposure settings so as to capture the picture the way our eyes saw them. Scene Modes incorporate this expertise and make it available to the inexperienced shooter: just select the appropriate scene you are trying to capture and leave it to the camera to make the necessary exposure adjustments.

Other features popular on P&S digital cameras are Face Detection (where the camera automatically detects and focuses on one or more faces in the scene), automatic Red-Eye reduction (when the light from the flash is reflected back from the back of the eye), shadow brightening and noise reduction.

But when the interest in photography grows and a person starts asking questions about how he or she can take a certain type of picture, a P&S digital camera, even with all the available shooting modes, may still not provide enough exposure flexibility. A beginner photographer needs a digital camera that allows control over all the exposure settings. Besides the shooting modes found on most P&S cameras, cameras geared for beginner photographers will also provide Aperture-Priority shooting mode, Shutter-Priority shooting mode, and full Manual shooting mode.

In Aperture-Priority shooting mode, you tell the camera which aperture to use and the camera then selects the appropriate shutter speed to obtain a correctly exposed picture. Typically, you would use a large aperture to limit depth of field and obtain blurred backgrounds, perfect for portraits. You use a small aperture to increase depth of field and obtain a picture that is sharp from foreground to background -- perfect for landscapes.

In Shutter-Priority shooting mode, you tell the camera which shutter speed to use and the camera then selects the appropriate aperture to obtain a correctly exposed picture. Typically you would use a fast shutter speed to "freeze" action, such as in sports photography. You use a slow shutter speed to "suggest" motion in your pictures due to the blurriness that results when a fast moving subject is photographed with a slow shutter speed. The quintissential example is photographing flowing water; a slow shutter speed captures the moving water as a cloud.

In full Manual shooting mode, the photographer has full control over all the settings of the camera. This provides the most exposure flexibility and allows for creative photography.

Digital cameras geared for serious photographers are similar to those for beginner photographers, except that they provide better image quality, more parameters you can have control over, faster and more precise auto focus, faster burst shooting, faster performance, availability of add-on lenses and filters, possibility to use a more powerful external flash, more buttons and external controls for quicker operation (instead of having to search in the MENU), etc.

Advanced photographers typically graduate to a Digital SLR which provides the ultimate in exposure control and flexibility. Performance is near instantaneous, image quality is excellent, and the lens is interchangeable, which means you have access to a specialized lens for almost any type of photography you may wish to pursue further. Accessories also abound.

Megapixels Resolution
How many megapixels resolution should your digital camera be able to capture? The more pixels you have, the larger the prints you can print. Consider the following table, and the answer becomes obvious:

It is not just a matter of print size, for you may not want to ever print your pictures. The print size gives you an indication -- serves as a proxy for -- the quality of the image you can capture. Here at Photoxels, we recommend that you consider only digital cameras with 3+ Megapixels resolution. This way, you will never regret capturing that superb shot -- but due to the low resolution of your digital camera, it does not display or print like the way you saw it in the viewfinder or on the LCD.

The higher megapixels also allows you to crop and enlarge ('digital zoom') your original image in an image editing software without noticeably losing too much quality.

[Editor's note: A note of caution is necessary here. The megapixels resolution of a digital camera is the number of pixels it uses to capture an image. In general, the more megapixels, the more detailed the image that is captured. However, the captured image is then saved, usually as a jpeg file which is compressed. Most digital cameras allow you to specify the amount of compression to use: the less the compression, the bigger the file and the more detailed the image saved; the more the compression, the smaller the file and the less detailed the image saved. However, many beginner cameras do not give you that option and save the image with a lot of compression. So, even if a digital camera is advertised as 5MP and theoretically you should be able to obtain a 20x30 in. print from it, the truth of the matter is that it may save its final image with too much compression to provide the amount of detail necessary to print such a large print.]

Storage Media
How much storage media is enough? Some beginners wonder why people get so hung up with large storage media when we previously could at most capture 36 exposures on film? They're wrong, of course, because we were never satisfied with 36 exposures and carrying all those rolls of film in our pockets were a real bother. Pros attach a film back to their SLR, giving them hundreds of exposures. Wonder why they would do such a thing? :)

Anyway, a good rule of thumb is the following: at least 128MB for a 3 megapixel digital camera and at least 256MB for a 4 megapixel digital camera. The reason that 'bigger is better' is because it's a real bother to change film or memory card (it usually happens when things just start to get interesting around you) and you risk missing a good picture. After all we are talking digital here, so forget the past. There's just no good reason to change memory cards. Having said that, it is always a good idea to have a spare memory card with you in the odd and rarest of unlucky chance that the first one should stop working for any reason (when this kind of rarest of event happens to you, it is a good time to go out and purchase a lottery ticket ).

You also want to shoot at the highest resolution at all times, which means that you need all the storage space you can get. Shooting at the highest resolution allows you to print a nice sized 8x10 in. photograph to hang on your wall or to crop a smaller part of the picture and blow it up without loss of quality.

Maximum Aperture
Why should you care what the maximum aperture is? Simple, the maximum aperture decides how much light your camera lets in to record the picture. The larger it is, the more light gets in, thus allowing you to shoot in a bigger range of lighting situations. With a large enough aperture, you could shoot on a cloudy day without the use of flash; you could shoot action pictures using a fast shutter speed; you could shoot portraits and throw the background out of focus.

If the maximum aperture is small to start out with, you can only shoot in a limited range of lighting situations, and would be overly relying on the flash to provide enough light to properly expose your shots. And more often than not, the camera flash is pretty weak and useful mainly as fill-in flash. You would be using slow shutter speeds which means that action shots without flash would be impossible. Slow shutter speeds also mean that any movement on your part (i.e. camera shake) results in blurred pictures.

Some digital cameras have a limited aperture range. Instead of an iris that opens (larger aperture, more light gets in and less depth of field) and closes (smaller aperture, less light gets in and more depth of field) in increments, they might have only 2 preset aperture settings. In fact, some might not have an iris at all, which means that you cannot really control depth of field. The aperture might be "electronically controlled" by moving a filter into the light path to cut off the amount of light reaching the image sensor; this, in effect, simulates a smaller aperture setting but depth of field is not affected. Is this good or bad? Well, the jury is still out on this one. Technically, 2 preset apertures with no ability to control depth of field is a limiting factor for those who want to explore digital photography, but if such a camera takes superb pictures, and you're just interested in point-and-shoot, then who is to complain? Keep an open mind, and don't judge a digital camera only by its features -- it's the picture quality that counts in the final analysis.

Optical vs. Digital Zoom
Which is better, a digital camera with 3x optical zoom and 2x digital zoom -- or one with 2x optical zoom and 4x digital zoom?

The answer is easy if you understand the difference between optical zoom and digital zoom.

With optical zoom, you use the optics of the camera to bring your subject closer, just like in a conventional non-digital camera.

Digital zoom is simply another fancy term to mean "blow up" -- as in "enlarge" -- the actual picture, which therefore always results in a loss of picture resolution. Just as in a film-based picture, enlarging the image magnifies the "grain" of the image, similarly digital zoom 'magnifies' the dots or pixels that make up the digital image (increases the "noise level").

[Editor's note: In reality, you do not really magnify a pixel, but as you enlarge the image, the gaps between pixels increase and the software 'extrapolates' -- guesses -- what color pixels should fill in the gaps.]

So now it becomes clear that digital zoom is, for comparison purposes, "useless." Why do we say that? Because you would always want the original picture in all its maximum resolution, and then enlarge it, if desired, in an image editing software later.

Is digital zoom then a totally "useless" feature for a digital camera to have? No! Read the above paragraph again: we said, "for comparison purposes." For arguments sake, let's say that if there is no appreciable loss in image resolution when you use digital zoom, and it helps you in composing a pleasant image, then it is a useful feature to have in your digital camera, and use it by all means. Again, what we are saying is, do not use digital zoom to compare cameras since the same effect can be accomplished in an image editing software.

Bottom line: When comparing digital cameras, always use optical zoom, not digital zoom. And ensure that any digital camera you purchase either allows you to disable digital zoom entirely or warns you clearly that it is switching to digital zoom. "Seamless" optical to digital zoom, without an appropriate warning, is not a good idea.

Shutter Speed
Your camera relies on the combination of aperture and shutter speed to determine proper exposure. If you have a wide range of shutter speeds, you have more latitude in deciding what aperture to use and what kind of pictures you can take. If you have a limited range of shutter speeds, or worse only three or four shutter speeds, you might find that most of your shots are underexposed, or the camera applies software techniques to "boost" the available light by manipulating the image captured, which usually results in loss of image quality. So, even though you might buy a high resolution digital camera, your limited shutter speed range may effectively diminish the image quality you obtain in capturing a properly exposed picture (e.g. the camera might have to use a higher ISO setting and introduce noise in your picture). Bottom line: ensure that your digital camera provides a full range of shutter speeds ranging all the way from fast (e.g. 1/1,000 sec.) to slow (1 sec. or more).

A Note on Shutter Speed/Aperture/ISO
To properly expose a picture, your camera needs to let in enough light to reach the film or image sensor (in the case of a digital camera). So, let's assume we set a fixed aperture (the opening of the iris in the lens that allows light in).

In a sunny situation, there's a lot of light, so a camera set on Auto mode will usually select a fast shutter speed (say, 1/125 sec. or 1/500 sec.) so the image sensor is exposed for only a short time to the light.

In a cloudy or dark situation, the camera on Auto mode will usually select a slow shutter speed (say, 1/30 sec. or 1/15 sec.) so as to allow the image sensor to be exposed for a longer time.

Basically that's how shutter speed works for a selected aperture. Usually, however, the camera on Auto mode will select different combinations of shutter speed and aperture to obtain proper exposure.

In general, the following applies: a small aperture means less light reaches the image sensor, so the camera needs to open the shutter for a long time; a large aperture lets in more light, so the shutter speed opens for a short time.

You can also set the image sensor sensitivity (ISO) to affect exposure. A high ISO needs less light, a low ISO needs more light for proper exposure. Common problem with current consumer digital cameras is that high ISOs introduce quite a bit of noise as to be mostly unusable, so don't get fooled by 'features on paper.'

White Balance
The image sensor in a digital camera does not "see" light the same way that film does. The sensor just receives light, generates an analog charge that must then be interpreted by software to digital pixels. This gives digital cameras the ability to adjust color in camera. What white balance allows a digital camera to do is to calibrate all the colors based on the color White. In finding a reference white, all other colors are adjusted accordingly. The better digital cameras allow you to calibrate the white balance using a white (or gray) card. Ensure that your digital camera allows you to select different white balance setting for different situations, such as outdoors, cloudy, fluorescent, and tungsten.

Exposure Control / Shooting Modes
Most consumer digital cameras today feature Scene Modes. Scene modes are simply preset exposure/shutter speed combinations (together with white balance and exposure compensation) to account for most of the common picture-taking situations, such as portraits, indoor fluorescent lighting, landscape, and night scene. Scene modes save you from having to fidget around with the aperture, shutter speed, white balance and exposure compensation to obtain proper exposure.

A note of caution is in order when talking about scene modes. The fact that a digital camera offers a particular scene mode does not necessarily mean that you will be able to capture good images with that scene mode. Let me elaborate in more detail, with the following examples, what I mean:

Let's say a digital camera offers a Sports or Action scene mode. You might think that this means you will be able to capture great action shots with this digital camera, right? Maybe. It all depends on what the digital camera offers technically.

To understand this completely, let's review what are the necessary technical requirements for being able to successfully freeze a fast action shot: 1) a fast shutter speed (say, 1/1,000 sec.); 2) a wide aperture (say, F1.8); 3) a powerful flash; 4) ISO of 400 and above; 5) white balance for fluorescent and tungsten lighting; 6) a small shutter lag (you'll never catch the action if the shutter clicks 2 sec. after you press the shutter release).

Let's assume your digital camera offers a shutter speed of 1/1,000 sec. -- fast enough to stop action. It has a maximum aperture of F2.8 -- OK for outdoors action shots in bright sunlight, OK for indoors action shots using a powerful enough flash, but not quite wide enough for indoors action shots where flash is not permitted. In the latter case, you've got no recourse but to increase the film equivalent sensitivity to ISO 400 or above. Now, there are not too many digital cameras, except for the very expensive digital Single Lens Reflexes (dSLRs), that deal well with the increase in noise level at the higher ISOs. And if your digital camera only offers a film equivalent of ISO 100, you're stuck! The Sports or Action scene mode on your digital camera is, for all practical purposes, useless to you if indoors action shots without flash is what you're after.

Similarly, Night Scene mode is really useful if a digital camera provides a shutter speed of 1 sec. and slower, and perhaps even bulb (where the shutter remains open as long as you depress the shutter release). But if the slowest shutter speed is 1/30 sec., ummm... not much is possible as far as night pictures are concerned even though the camera offers a Night Scene mode.

[Not exactly a scene mode, but also consider the case of a digital camera that offers ISO sensitivity of 100, 200, 400 and 800. But, if the noise level at ISO 200 and higher is unacceptable, then, for all practical purposes, the higher ISOs are useless (unless a 'noisy' picture is the 'image effect' you're after). So, when comparing digital cameras, do not trust 100% the features on paper -- it pays to read actual users' opinions to ensure whether a particular feature is usable in practice.]

Ensure that the camera can technically fulfill whatever requirements are necessary to capture the shots you're after. Review our tutorial for further details about the technical requirements for scene modes.

Light Metering
To properly expose a picture, your camera has to measure how much light is available. Suppose you are shooting a picture where your main subject is in the shade but it is otherwise a very bright sunny day. If the camera takes a Centre Weighted-Average light measure, it gives extra weight to the centre of the frame, then averages it with the rest of the frame. If the surrounding light is bright enough, the meter might be "fooled" by the bright light all around your main subject, and the main subject might come out underexposed. In this case, it might be better to switch to Spot Metering so your camera takes its light measurement only on your main subject. The result is that the main subject is now properly exposed, though the surroundings might be somewhat overexposed, which might be OK in this particular situation. Matrix Metering takes light measurement from various areas of the framed shot and then sets the exposure accordingly. Different cameras have different light metering schemes, but they are mostly variants of the three basic ones we have just discussed. You would want to favor digital cameras that give you spot metering, plus one or both of the other two light metering options.

Lens

The lens is easily one of the most important element of a digital camera. It receives and focuses the light from your scene onto the image sensor, and if the lens quality is poor, then you are already starting out with a poor quality image.

If you're using a digital SLR camera (DSLR), the lens is interchangeable, i.e. you can remove the one currently attached and attach a new one. You can thus purchase the lens that suits the type of photography you're most interested in doing: macro lens for close ups, wide-angle lens for landscapes, telephoto lens for sports, etc. When we are talking about non-DSLR cameras, the lens is permanently attached to the camera, and we say that the lens is "fixed." It is, in most instances, a zoom lens with macro capability. In other words, manufacturers try to provide you a versatile lens that can take pictures in many situations: close ups, wide-angle, telephoto, etc. Its image quality is often not as good as a dedicated interchangeable lens.

When you look at the numbers given for a lens, it can get confusing, but it's quite simple really. Typically, you'll read something like this:

f=25-250mm 1:2.8-5.3

The "f=25-250mm" part says that the lens has a starting focal length of 25mm and ending focal length of 250mm. If we divide 250 by 25, we get 10, so it's a 10x zoom lens. Note that a f=35-350mm is also a 10x zoom lens. So, when you hear about zoom power, you also need to know the starting and ending focal lengths to get a better idea of what the lens is capable of.

We generally call a lens with a focal length of around 50mm a standard lens. This is because the angle of view of the lens approximates our own eyes' angle of view. So the lens "sees" what our eyes see. In fact, some photographers even call a 35mm a "standard" lens since we do have peripheral vision and do move our head left and right a bit even when we're just looking straight ahead.

Anything less than 50mm is known as wide-angle: e.g. 35mm, 25mm, etc. At 25mm and less, we further qualify the lens as "ultra" wide-angle. And when the angle of view approaches 180° we call the lens a "fish-eye" since [some] fishes apparently can see 180 degrees all around. The wider the angle of view, the more scene you can capture: your group shots can contain more friends and family members without you having to back all the way to Katmandu to include everyone in, and your landscape shots approximate what we typically see when we move our heads left and right looking at a scene.

Any focal length greater than 50mm is known as a telephoto (or simply tele, for short). Lenses with focal lengths of 75mm, 100mm, 135mm, 200mm are known as medium tele, whereas those at 300mm and above are generally referred to as long tele lenses. The longer the focal length, the narrower the angle of view, and therefore the closer you can get to a far away subject, without having to walk close to it. Telescopes are basically long tele lenses.

If we build a lens where we can change its focal length by moving one or more lens elements inside, we end up with a zoom lens. Sports photographers who take pictures far from the action need a tele lens, so they typically buy a tele zoom lens, say with focal lengths ranging from 100mm to 300mm (a 3x zoom lens). This allows them to cover action that occurs far away (using 300mm) as well as closer (using 100mm), and anything in between. Typically, on fixed lens cameras, a good zoom lens should have a focal length range that covers a satisfying wide-angle (say, 25mm) to a medium tele (say 125mm). Dividing 125 by 25, we get a 5x zoom lens, but as you can see the zoom power itself is not as important as knowing the starting and ending focal lengths. This allows us to take large group shots and wide landscapes as well as nice portraits (without getting in our subject's face). If you want an even more versatile zoom lens, our previous example of a 10x 25-250mm zoom lens would cover wide-angle to long tele.

There are some fixed lens cameras that also have a fixed focal length lens. The first "fixed" refers to the fact that the lens is not interchangeable; the second "fixed" refers to the fact that the lens is not a zoom lens, i.e. it has only one focal length, usually a wide-angle or standard focal length lens.

The "1:2.8-5.3" part says that the lens has a maximum aperture of f/2.8 at max. wide-angle and f/5.3 at max. tele. As we've already explained above, the wider the aperture, the better the light gathering ability of the lens.

You would usually not be concerned with the diameter of the lens. The diameter is what it is, and it's not something you have much of a choice about. You need to be aware of it if the lens is threaded and allows you to screw a filter on. The diameter tells you the diameter of the filter you should purchase.

Panorama (Stitch Assist) vs. Wide-Angle
An interesting development with digital cameras is the "panorama" or "Stitch Assist" feature which allows you to take a number of regular shots and digitally "stitch" them together in an image editing software to produce a panoramic picture. This is a great development and panoramic pictures can be breathtaking to view. It is very impressive when used to take a large group of people, say a club's members or a large family with grandparents and grandchildren, all lined up. Panoramic landscapes are my favorites.

[Editor's note: Do not be confused with the 'Panorama' feature on film APS cameras. This is nothing but an after-the-fact in-the-photo-lab cropping and enlargement. In fact, no matter which picture mode you select, the film APS camera always capture the picture in the 'H' picture mode. In the photolab, the printer reads which mode you selected, then just crops and enlages it to 'simulate' the desired effect. Bottom line, it ain't panoramic and shouldn't really be called panoramic. It can give a nice effect sometimes, though, when used imaginatively.]

Some people have confused the ability of a digital camera to take panoramic pictures with the ability of a lens to provide a good wide-angle coverage. It is an understandable confusion, but really, it is not the same thing and we do not get the same results when either displaying on a PC monitor or in prints.

A lens with a good wide-angle coverage (say, 24 mm) will allow you to include more of the picture in the same one frame. To contrast, a panoramic picture needs many frames to cover the same angle. In other words, I can capture all the glory of a breathtaking view with a wide-angle lens and display it on my PC monitor. With panoramic pictures, the same coverage will be bigger than your PC monitor and you'll have to scroll left and right to view the image. Ditto, on an 11x14 in. print. Different beasts for different purposes.

I hope this clarifies the difference a bit. We are all awaiting camera manufacturers to bring out digital cameras with better wide-angle coverage. I'd rather have a lens with 28-112mm coverage (4x optical zoom) than one with 35-140mm coverage (also 4x optical zoom). With the first one, I get a good wide-angle at 28mm, normal coverage at 50mm, and a good portrait coverage at 112 mm (all using 35mm camera equivalent). With the second, I get normal coverage at 35mm, a good portarit coverage at 112-135mm, and so-so telephoto coverage at 140mm.

Please give us your feedback on this article and anything else you wished explained -- in addition or better.

Related Articles and Tutorials:

• Optical vs. Digital Zoom
• What Is... Correct Exposure?
• What Is... Aperture?