philip.greenspun.com/photography/building-a-digital-slr-system
With the recent introduction of came ras such as the Nikon D70s and the Canon Digital Rebel XT the market for digital SLR cameras has expanded tremendously. A point-and-shoot compac t digital camera can offer reasonably good image quality but a digital S LR, 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 i s necessary to use higher ISO speeds * interchangeable lenses 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 t he camera captures the image immediately. If you need to zoom or focus m anually there are large rings that you can operate quickly by feel. If y ou see a beautifully-lit scene you can capture that beauty instead of us ing an on-camera flash to blast everything with harsh white light. If yo u need to make a specialized photo you can buy or rent a specialized len s and attach it to the camera. This article explains the different kinds of digital SLR cameras availabl e, how to choose the right one for you, and what to do once you get it h ome from the shop. A digital SLR camera system, complete with lenses and accessories, can cost anywhere from $1,000 to $10,000. This article sho ws you how to choose and buy the basic items first and the more expensiv e and hard-to-use components later.
Olympus E1 Four-Thirds System Camera and 14-54mm zoom lens The single lens reflex (SLR) is most folks' idea of a serious camera. "SLR" means t hat the same lens is used for viewing and taking pictures. A mirror in t he body directs the light from the lens up into a prism for viewing, the n 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 o f 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 per haps 1/60th of a second. A Canon Digital Rebel or Nikon D70s looks very similar and works in almost the same way. The only difference is that in stead of a piece of film behind the shutter there is an electronic senso r 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 s ee what the sensor will see. The same can be said for the LCD displays o n the back of a $200 point-and-shoot camera but those displays are diffi cult to interpret in sunlight. The typical digital SLR camera viewfinder offers additional information underneath the image, including all the m ost important camera settings. The SLR is much larger and heavier than point-and-shoot camera. If you ar e leaving the house to socialize and want a camera to keep in your pocke t just in case an interesting photo presents itself, the SLR will seem c umbersome. If you are heading out specifically with a photographic proje ct in mind you will appreciate how the SLR and its controls fit into you r hands.
The fou ntain in Piazza della Rotunda, in front of Rome's Pantheon Because digital SLRs are more expensive than point-and-shoot cameras the manufacturers typically put in faster computers and better autofocus sys tems. 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, t he 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 e lements, as a high-end point-and-shoot. Resolution is important if you intend to make large prints bu t dynamic range, the ability to capture detail within bright highlights and dark shadows, is more critical in many situations. The sensors in di gital 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 mor e photons of light will fall on any given pixel. If during an exposure 5 0 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. An SLR system includes a bod y, 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 t he 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 desi gn and a lens that works on, say, a Nikon camera cannot be attached to a Canon body. The same companies that made 35mm film SLRs make digital SLRs. If you hav e a lot of Canon EOS lenses from your days as a film photographer, for e xample, you will probably want to buy a Canon EOS digital camera, becaus e those lenses from the 1990s will work just fine on the new digital cam era. The market leader in the professional/advanced amateur photography world is Canon. If you don't have a major investment in lenses you will probab ly want to buy a Canon digital SLR. The number two spot is occupied by N ikon, which is also a reasonable choice. Fuji and Kodak have made digita l SLRs that accept Canon- and Nikon-mount lenses. Once you get beyond Ni kon 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 sha re to invest enough money to build competitive bodies. Leica, Minolta, O lympus, Pentax, and Sigma are the small vendors in the digital SLR marke t Unless you have an enormous investment in lenses for one of these bra nds the only one of these worth considering for purchase is Olympus, due to its innovative Four-Thirds system, discussed below. There are three kinds of digital SLR systems being made as of September 2 005: 1 big lenses, big sensor 2 big lenses, small sensor 3 small lenses, small sensor We will discuss each in turn.
Can on and Kodak have taken the most obvious approach to the challenge of tr ansitioning from film to digital: build a digital sensor exactly the sam e size as one frame of 35mm film. The result is a chunk of silicon 24x36 mm in size, which is vast compared to the sensor in a point-and-shoot di gicam. The benefit of this vast sensor is reduced noise, which looks lik e 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 expe nsive. The only consumer-priced camera in this category is the 12-megapi xel Canon EOS-5D ($3300;
It is probably the best digital camera made and produces image qua lity that rivals medium format film (eg, 6x6cm Hasselblad). The only o ther full-frame digital SLRs made were the discontinued Kodak DCS Pro SL R/n and SLR/c bodies. The Kodaks were cheaper than the Canon but not qui te as functional and the fact that they were discontinued is a good illu stration of why you want to buy a digital SLR from a market leader. 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 s ensor 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 ...
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