Digital single-lens reflex (SLR) cameras are the standard tool for
serious photographers. With the introduction of cameras such as the
Nikon D40/D40x (current entry-level model is the Nikon D3000) and the
Canon Digital Rebel XTi (current entry-level model is the Canon Rebel T3),
the market for digital SLR cameras has expanded tremendously. A
point-and-shoot compact digital camera can offer reasonably good image
quality, but a digital SLR, which usually looks a lot like an old
standard 35mm film camera and may use the same lenses, offers the
following advantages:
accurate, large, and bright optical viewfinder
fast operation and large controls
excellent image quality in low "available" light situations when it
is necessary to use higher ISO speeds
interchangeable lenses
For more information on what to consider when purchasing a DSLR,
including details on lens compatibility, system expandibility, size
and weight, ISO settings, noise levels, etc, take a look at Bob
Atkins' article on Factors to Consider when
Choosing a Digital SLR Camera.
With the digital SLR you have a good idea of what you're going to
capture by looking through the viewfinder. When you press the shutter
release the camera captures the image immediately. If you need to zoom
or focus manually there are large rings that you can operate quickly by
feel. If you see a beautifully-lit scene you can capture that beauty
instead of using an on-camera flash to blast everything with harsh white
light. If you need to make a specialized photo, you can buy or rent a
specialized lens and attach it to the camera.
This article explains the different kinds of digital SLR cameras
available, how to choose the right one for you, and what to do once you
get it home from the shop. A digital SLR camera system, complete with
lenses and accessories, can cost anywhere from $600 to $10,000. This
article shows you how to choose and buy the basic items first and the
more expensive and hard-to-use components later.
The single lens reflex (SLR) is most folks' idea of a serious
camera. "SLR" means that the same lens is used for viewing and taking
pictures. A mirror in the body directs the light from the lens up into a
prism for viewing, then flips up out of the way just before an exposure
is made. The standard photojournalist's Nikon from the 1960s or 1970s
was an SLR with a roll of 35mm film behind the mirror. When the mirror
came up the light passed through to the shutter, which opened to expose
one frame of film for perhaps 1/60th of a second. A Canon Digital Rebel
or Nikon D80 looks very similar and works in almost the same way. The
only difference is that instead of a piece of film behind the shutter
there is an electronic sensor.
The mirror and optical viewfinder are what enable a photographer to
frame images more quickly and accurately than with a point-and-shoot
camera. Regardless of what lens or filters you have attached to the
camera you see what the sensor will see. The same can be said for the
LCD displays on the back of a $200 point-and-shoot camera but those
displays are difficult to interpret in sunlight. The typical digital
SLR camera viewfinder offers additional information underneath the
image, including all the most important camera settings.
The SLR is much larger and heavier than the point-and-shoot camera. If you
are leaving the house to socialize and want a camera to keep in your
pocket just in case an interesting photo presents itself, the SLR will
seem cumbersome. If you are heading out specifically with a
photographic project in mind you will appreciate how the SLR and its
controls fit into your hands.
Because digital SLRs are more expensive than point-and-shoot cameras the
manufacturers typically put in faster computers and better autofocus
systems. This makes the cameras more responsive and you are more likely
to catch the "decisive moment" as the baby's face lights up with a
smile, the soccer ball leaves the player's foot, or the dog catches the
frisbee.
A digital SLR may offer the same number of megapixels, individual image
elements, as a high-end point-and-shoot. Not all pixels are created
equal, however. Resolution is important if you intend to make large
prints but dynamic range, the ability to capture detail within bright
highlights and dark shadows, is more critical in many situations. The
sensors in digital SLRs are typically much larger than those found in
point-and-shoot cameras. The main advantage of a larger sensor is
better performance in dim light. If there are 8 megapixels spread out
over a sensor that is 4 times larger than the sensor in a
point-and-shoot camera that means more photons of light will fall on any
given pixel. If during an exposure 50 photons would fall on the small
sensor then 200 photons would fall on the big sensor. If there is a
small change in the light from one part of the scene to another the
sensor in the point and shoot camera is trying to notice a single extra
photon; the electronics in the camera with the big sensor have four
extra photons that are much easier to detect.
First-time consumers of digital SLR cameras focus on the body.
Long-time photographers, however, look at the system. An SLR
system includes a body, multiple lenses, flash units, and
various connecting cords. For most photographers the investment in
lenses will come to dwarf the cost of a body. It is thus important to
choose a system whose manufacturer makes the lenses that you need for
all of your potential projects and, ideally, whose system is popular
enough that you can rent special-purpose lenses for uncommon
situations. Each camera system has its own lens mount design and a lens
that works on, say, a Nikon camera cannot be attached to a Canon body.
Who makes digital SLR cameras?
The same companies that made 35mm film SLRs make digital SLRs. If you
have a lot of Canon EOS lenses from your days as a film photographer,
for example, you will probably want to buy a Canon EOS digital camera,
because those lenses from the 1990s will work just fine on the new
digital camera.
The market leader in the professional/advanced amateur photography world
is Canon. If you don't have a major investment in lenses you will
probably want to buy a Canon digital SLR. The number two spot is
occupied by Nikon, which is also a reasonable choice. Fuji and Kodak
have made digital SLRs that accept Canon- and Nikon-mount lenses. Once
you get beyond Nikon and Canon it becomes very difficult to rent lenses
and the companies that make the more obscure systems don't have a large
enough market share to invest enough money to build competitive bodies.
Leica, Minolta, Olympus, Pentax, and Sigma are the small vendors in the
digital SLR market. Unless you have an enormous investment in lenses
for one of these brands the only one of these worth considering for
purchase is Olympus, due to its innovative Four-Thirds system, discussed
below.
What kinds of digital SLRs are available?
There are three kinds of digital SLR systems being made as of September 2005:
big lenses, big sensor
big lenses, small sensor
small lenses, small sensor
We will discuss each in turn.
Big lenses, big sensor. Canon and Kodak have taken the most
obvious approach to the challenge of transitioning from film to
digital: build a digital sensor exactly the same size as one frame of
35mm film. The result is a chunk of silicon 24x36mm in size, which is
vast compared to the sensor in a point-and-shoot digicam. The benefit
of this vast sensor is reduced noise, which looks like grain, in low
light/high-ISO situations. The drawback of a vast sensor is that
manufacturing a flawless piece of silicon this big is very
expensive. Consumer-priced cameras in this category include:
Canon EOS 5D, (compare prices) (review), Canon EOS 5D Mark II, (compare prices) (review),
Nikon D700, (compare prices) (review), Nikon D3, (compare prices) (review), and
Sony Alpha A900, (compare prices) (review). If you have a strong back and an
unlimited budget, the Canon EOS 1Ds Mark III, (compare prices) (review), is a
great choice. It is probably the best digital camera made and produces
image quality that rivals medium format film (e.g., 6x6cm Hasselblad).
The only other full-frame digital SLRs made were the discontinued Kodak
DCS Pro SLR/n and SLR/c bodies. The Kodaks were cheaper than the Canon,
but not quite as functional and the fact that they were discontinued is
a good illustration of why you want to buy a digital SLR from a market
leader. I own a 5D and have written a full review of the Canon EOS 5D.
Big lenses, small sensor. In order to keep the cost of the body
within a range of $700-1500 and allow photographers to use their old
35mm system lenses most digital SLRs fall into this category. The front
of the body has the same lens mount as an old film SLR. The back of the
body has a sensor that is smaller than the 24x36mm standard frame of an
old film SLR. The result is a camera that looks the same as the old
film camera but multiplies the magnification of all the lenses. Having
a smaller sensor is like cutting the center out of a drugstore proof
print. You don't capture all the information on the left and right and
top and bottom of the frame. It is as though you took the picture with
a telephoto lens. The viewfinder has been adjusted so that what you see
optically is what is captured in the digital file. If you're coming
from the film world you will need to do a mental adjustment. A 50mm
normal perspective lens on a big lens/small sensor camera behaves like
an 80mm telephoto lens on a film camera. A 20mm ultra wide-angle lens
behaves like a 30-32mm slightly wide angle lens on a film camera.
Nearly all the popular digital SLRs fall into this category and their
various merits will be discussed below.
Small lenses, small sensor. The biggest problem with the "big
lens, small sensor" situation is that photographers are forced to cart
around lenses that are much larger, heavier, and, theoretically, more
expensive, than they need to be. A big heavy Canon telephoto lens is
big and heavy mostly because it is built to cast an image circle large
enough to cover a 24x36mm frame but the Canon EOS 30D body's sensor is
only 15x22mm in size. Any engineer would look at this "big lens, small
sensor" situation and say "Why not come up with a standard reasonable
sensor size and then make lenses that are just large enough to cover
that sensor with an image?" That's precisely what the Four Thirds
consortium did. Olympus and Kodak seem to be the originators of the
standard but Fuji, Panasonic, Sanyo, and Sigma have signed on as well
according to www.four-thirds.org. This seemed
like a great idea at the time (2002) but four years later only three Four
Thirds system bodies have been built, all by Olympus, and only a
handful of lenses, all from Olympus and Sigma.
If you have a a robust checking account and/or a lot of Canon EOS
film camera lenses an unlimited budget the "full-frame" Canon EOS-5D
(big lenses/big sensor; medium weight; $2900) is the obvious choice.
If you don't need state-of-the-art performance and value compactness
above all, the Olympus E System is a reasonable choice (see my review of the Olympus E1 More than
50% of all photographers find that the engineering compromise of "big
lenses/small sensor" fits their budget and needs. This has led to the
introduction of lenses that have the big lens mount for a 35mm film
camera but optically cover only the small sensor of a mid-range
digital SLR. These are sold as "digital-only lenses" or "digital
camera lenses" but in fact they won't work on a full-frame digital
SLR--the corners of the image would be black. Canon denotes these
lenses as "EF-S", Nikon as "DX".
