building a dslr
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Building a digital SLR system: Looking at the Canon Digital Rebel
Exit, Nikon D40, Nikon D80, and EOS 5D cameras
By Philip Green spun
Digital single-lens reflex (SLR) cameras are the standard tool for serious photographers. With the introduction of
cameras such as the Nikon D40 and the Canon Digital Rebel Exit 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 its
necessary to use higher ISO speeds
For more information on what to consider when purchasing a DSLR, including details on lens compatibility,
system expandability, 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 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.
[If you don't want to read this article and are impatient to get started immediately, get a Canon Digital Rebel Exit
(review) and Sigma 30mm f/1.4 EX DC for Canon, $439; if you must have a zoom, the Canon EF-S 17-55 f/2.8 IS
USM, $990 (review)is a good choice.]
What is a single-lens reflex (SLR)?
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, and then flips up out of the way just
before an exposure is made. The standard photojournalist's Nikon from the 1960s or
1970swas 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 held displays on the back of a $200 point-and-shoot camera but
those displays are difficult to interpret in sunlight. The typical digitally 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:
1. big lenses, big sensor
2. big lenses, small sensor
3. 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 of35mm film. The result is a chunk of silicon 24x36mm in size, which is vast
compared to the sensor in a point-and-shoot digital. The benefit of this vast sensor is
reduced noise, which looks like grain, in lowlight/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 (review), Canon EOS 5D Mark II
(review),Nikon D700, $2350 (review), Nikon D3 (review), and Sony, $2500 (review). If you
have a strong back and an unlimited budget, the Canon EOS 1Ds Mark III, $6079 (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
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 old35mm 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