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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
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.
How many megapixels
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.
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.]
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.
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
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").
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
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
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
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.
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
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.'
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
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
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.
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
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.
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
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