Greater shooting flexibility.
The capability to change ISO sensitivity, white balance, and a host of other image parameters from shot to shot. | Much greater power consumption.
Digital SLR batteries are bigger, more complex, and more expensive. Plus, keeping them charged and ready is a critical part of your photography routine. All about digital SLR sensors Sensor types  Fujifilm's SuperCCDs use a
honeycomb layout for photodiodes
and the color-filter layer. CCD (charged-coupled device)
Currently the most common type of digital SLR sensor. Almost every dSLR manufacturer offers at least one CCD-based model.
Pros: Traditionally, the highest image quality, pixel for pixel. Current sensors include innovative chip architectures designed to enhance dynamic range or speed.
Cons: Most expensive. Most power-hungry.
 The CMOS sensor used in Canon's
Digital Rebel XT. CMOS (complementary metal-oxide semiconductor)
Initial implementations took advantage of CMOS' on-chip electronics to make cheap but noisy sensors. Stripping off the extra circuits increased each pixel's light-collecting area, thereby boosting sensitivity and quality to surpass that of many CCDs.
Pros: Theoretically, lower production cost. Uses less power than CCD.
Cons: CMOS sensors tend to be bigger than their CCD equivalents, resulting in larger cameras.
The bottom line on sensor types
Ignore the theoretical claims and judge the cameras, not the sensor types. We've seen great photos--and crummy ones, too--from digital SLRs with every technology.
Sensor sizes Nearly all digital SLR sensors are much bigger--and consequently much more expensive--than the thumbnail-size imagers in point-and-shoot digicams. Current digital SLR models use these sensor sizes.
Four Thirds
The specified sensor size for the Four Thirds format, an open digital SLR standard created by Olympus and Kodak.
Dimensions: 17.3mm by 13mm
Example cameras: All Olympus, Panasonic dSLRs
APS
A loose term for imagers that are approximately the size of the APS-C or APS-H film formats. Most digital SLRs use this size.
Dimensions: Varies, APS-C (ranges from about 14mm by 21mm to 16mm by 24mm), APS-H (28.7mmx19.1mm).
Example cameras: Canon EOS Digital Rebel XSi, Nikon D80, Sony Alpha DSLR-A350, Canon EOS-1D Mark III
35mm-film format
Often called full-frame, to indicate that the sensor is the same size as a standard frame on a roll of 35mm film. Sensors this big are very expensive to build, but they eliminate the so-called focal-length magnification factor (see page 4 for more on this).
Dimensions: 24mm by 36mm.
Example cameras: EOS-1Ds Mark III, Canon EOS 5D, Nikon D3
Geek note
Larger sensors are the secret to why 10 megapixels from a digital SLR beat 10 megapixels from a consumer digicam. To spread the same number of pixels over a larger sensor area, the pixels (technically, photosites containing diodes) must be bigger. These bigger photosites gather more light, so they produce less-noisy images, capture greater dynamic range, and perform much better at high ISO settings.
 This image shows the actual sizes of the sensors used in digital cameras, from the tiny chips in compact cameras to the large, 35mm-film-size sensors in some high-end digital SLRs. So what sensor resolution do I need? The short answer
Any current dSLR has sufficient resolution to handle Web or newspaper reproduction. For magazines and large print sizes (16x20 inches and greater), especially where you'll be cropping for detail, 8 megapixels is a good starting point. Fine-art landscape photographers and others seeking maximum detail should consider 10-megapixel-plus digital SLRs.
The long answer
Do the math. For example, let's say you're making an 8x10-inch print on an inkjet printer.
Step 1:
Figure out the required output resolution.
Our inkjet printer produces best results at a resolution of 240 pixels per inch or greater.
Step 2:
Multiply the required output resolution by the linear dimensions of your final print.
8 inches x 240 pixels per inch = 1,920 pixels required for the vertical dimension
10 inches x 240 pixels per inch = 2,400 pixels required for the horizontal dimension
Step 3:
Multiply vertical by horizontal.
1,920 x 2,400 = 4,608,000, or 4.6 megapixels, is our minimum required resolution.
Step 4:
Accommodate some overhead for cropping.
If you think you'll usually crop out about 30 percent of a photo, add 30 percent more pixels to the minimum required resolution.
4.6 megapixels x 1.3 = 5.9 megapixels
Keep in mind:
The math outlined above isn't written in stone; you can usually get good large prints even when you scale an image's resolution up in a program such as Photoshop.
What about dust? Every time you change the lens, you run the risk of dust getting on the sensor, which at best can result in bad pixels you'll need to retouch out of your photos and at worst can muck up your camera's insides. Unless you shoot in very dusty, sandy, or otherwise particulate-heavy environments, and if you take reasonable care when you swap lenses, dust shouldn't be a huge worry; most cameras include a combination of antidust technologies, such as vibrating the sensor on startup to dislodge particles. If you are partial to shooting around dirt and sand, then you may want to search for discussions about the efficacy of various systems. Some sites, such as Chasseur d'Images, ran comparative tests in 2007 and concluded that Olympus had the only decent performance in this area. However, a year (or more) is a long time in a camera product cycle, and the results may have changed with subsequent generations of cameras.Digital SLR lens considerations Focal-length multiplier We already noted that most digital SLRs use APS-size sensors, which are smaller than a 35mm-film frame. This gives rise to a confusing notion variously called focal-length magnification, focal-length multiplier, crop factor, or lens conversion factor, which requires a brief lesson in camera optics:
Example:
On a Nikon D300, which has an APS-size sensor and a resulting focal-length multiplier of 1.5x, a 50mm lens captures the same angle of view that a 75mm lens would on 35mm film (50mm x 1.5 = 75mm). Since we're used to thinking about our lenses in 35mm-film terms, it's convenient to say that a 50mm lens "acts like" a 75mm lens when it's used on a D300. And a 28mm acts like a 42mm, a 200mm like a 300mm, and so on. It's an oversimplification--only the angle of view changes--but we won't squeal to the optics police.
However, the focal-length multiplier doesn't affect the lens distortion inherent in a wide-angle lens. In other words, on that D300, a 33mm lens would have the same angle of view as a 50mm lens, but it would still have the barrel distortion characteristics of a 33mm lens--not the normal, portrait-friendly characteristics of a 50mm model.
Pros:
Sports and wildlife shooters love the way all their lenses seem to be longer than they were on 35mm cameras. Cheaper medium-range zooms work as if they were megabucks supertelephotos.
Cons:
Landscape and architectural shooters can't get lenses that are wide enough for their subjects--or they're forced to buy a very pricey superwide lens, such as a 14mm.
If you find all this is maddeningly confusing, one option is to pony up the big bucks for a camera with a full-frame sensor, such as the Canon EOS 5D, so all of your lenses will perform just as they would on a film SLR.
"Made for digital" lenses Another brief lesson in camera optics:
A lens projects a circular image towards the sensor. This image circle must be big enough to cover the whole area of the sensor; otherwise, you'll see vignetting, which is dark corners and edges in your pictures.
Lenses for APS digital
Some manufacturers make "digital only" lenses, which project smaller image circles--just big enough to cover the APS sensor frame but not big enough for the 35mm film frame for which previous lenses were designed. In theory, the companies can reduce size and weight and save money by doing this, but these lenses won't work on your backup film-camera body or on a future digital SLR with a 35mm-size sensor.
Examples: Canon EF-S, Nikon DX
The Four Thirds design:
Unlike film, digital sensors can produce unwanted artifacts when light rays from the lens strike the sensor at oblique angles. One of the main selling points of the Four Thirds format is that its lenses will refract light rays to strike the imager close enough to perpendicular to avoid problems. We think the jury is still out on whether this issue is really significant or not.
Manufacturers: Olympus, Panasonic
| Other notable lens features |
|---|
| Image stabilization | IS (Canon)
VR (Nikon)
OS (Sigma) | A mechanism in the lens detects and counteracts camera shake, reducing blur in handheld shots at slower shutter speeds. Note that Sony, Pentax, and Olympus offer an alternative to lens-based stabilization by incorporating image stabilization into the camera body. This allows you to use optical image stabilization with any lens. Lens stabilization and body stabilization are equally effective, but you can only preview the stabilized image in a lens-based system. | | Ultrasonic focusing | USM (Canon)
SWM (Nikon)
HSM (Sigma)
SWD (Olympus)
SSM (Sony) | Virtually silent piezoelectric motors provide the best focusing speed and responsiveness. | | Apochromatic correction | UD (Canon)
ED (Nikon, Olympus, and Sony)
APO (Sigma)
LD (Tamron)Digital SLR performance and features As with standard digicams, digital SLR features and performance vary widely. These are some of the most important differentiators.
| Performance and feature criteria |
|---|
| Resolution | Low end: 6 megapixels
High end: 21 megapixels | | Frame rate | Low end: about 1.5fps to 4fps
High end: 10fps | | Burst depth | Low end: 4 to unlimited shots
High end: 7 to unlimited shots | | AF speed and tracking | Hard to quantify, but there are wide gaps in the AF performance of current digital SLRs, especially when tracking moving subjects. The top-end sports and news pro cameras definitely outperform the rest. | | Ruggedness | Also hard to quantify, but another area where a wide gap exists between low-end offerings and the midrange-to-top sports and news pro cameras, which are sealed against moisture and made with more durable materials. | | Viewfinder coverage and effective magnification | Low end: 95 percent or less; below 0.58x
High end: 100 percent; 0.58x or higher
The effective magnification of a viewfinder is the optical magnification corrected for the focal length multiplier. For example, a dSLR with a stated/optical magnification of 0.94x and a 1.5x focal-length multiplier (APS-C sensor) would be 0.94 * 1.5 = 0.63. That's why Four Thirds-based cameras have stated magnifications over 1.0--they have to compensate for the 2x multiplier of the small sensor. Higher effective magnification and coverage is always better. | | Start-up, playback, mode-switching times | Low end: 1- to 6-second delays
High end: Virtually instantaneous | | Viewfinder information | Varies widely. The more information you can see without taking your eye away from the viewfinder, the faster you can shoot. | | Quality of auto white-balance system | None is perfect, but a good one saves lots of time and headaches for JPEG shooters. Those who shoot raw files have the option of correcting white balance with software after shooting. | | Ergonomics | Impossible to quantify--and partly a matter of personal preference--but critical to efficient shooting. Our advice: try before you buy. | | Image stabilization | Lens or body? With respect to the final photo produced, both work equally well. Optical stabilization has the advantage of letting you see the stabilized version while you're looking through the viewfinder, which can be crucial when framing at long focal lengths (beyond 300mm), but putting the technology in the lens generally results in more expensive lenses. On the other hand, mechanical (sensor-shift) stabilization will work with any lens you buy, making it a less-expensive long-run solution. | | Video capture | Low end: 24 or 30fps 1,280x720 video encoded with Motion JPEG as an AVI file.
High end: 30fps or better 1,920x1,080 video encoded with H.264 in MPEG-4 or Quicktime MOV format. Manual shutter speed and aperture controls.Which digital SLR camera is right for me? Dabbler I'm exploring photography as a fun hobby but getting serious enough for an SLR and a few lenses. I devote some of my time specifically to photography when I travel. I sometimes have my nephews and nieces pose for me at family gatherings, and I have several hundred pictures of the family cat. I'm thinking about taking a weekend photo seminar. I might make a 16x20-inch print of a great shot and frame it.
| Key Features |
|---|
| Price: | Less than $600 for body and starter lens | | Resolution: | 6 to 15 megapixels | | Ruggedness: | Any | | Frame rate: | 2fps to 5fps | | Burst depth: | 5 to 6 shots | | AF speed and tracking: | Low end to midlevel | | Video: | Uncommon at this price, but might have 24 or 30fps (or their PAL equivalents) at 1,280x720, using Motion JPEG codec. | | Also look for: | Good image histogram; compact body smaller than 24 ounces; lightweight zoom lenses |
Student I'm studying photography and seriously thinking about it as a career. I'm trying out many different styles and disciplines: fine art, photojournalism, commercial, portrait, and wedding. I submit some photos to newspapers and magazines, and I print as large as my budget allows.
| Key Features |
|---|
| Price: | Less than $1,000 for body and starter lens | | Resolution: | 12 to 18 megapixels | | Ruggedness: | Metal or hybrid metal-polycarbonate body; heavier-duty lenses | | Frame rate: | 5fps to 8fps and faster | | Burst depth: | 10 shots or more | | AF speed and tracking: | The best you can afford | | Video: | 24 or 30fps (or their PAL equivalents) at 1,920x1,080, using H.264 codec in MPEG-4 or QuickTime MOV files. | | Also look for: | good image histogram; comprehensive viewfinder information display; good raw-conversion software; tethered operation; comprehensive flash-control features |
News, sports, and action photographer I'm a pro or a serious amateur who shoots breaking news; college or professional sports; or serious adult recreational leagues, competitions, and activities. My photos are printed in magazines and newspapers or posted on the Web. I might make prints as large as 16x20 inches.
| Key Features |
|---|
| Price: | As much as $5,000 for the body | | Resolution: | 10 or more megapixels | | Ruggedness: | All metal, moisture- and weather-resistant | | Frame rate: | 8fps to 10fps | | Burst depth: | 40 shots or more | | AF speed and tracking: | The best currently available | | Video: | 30fps (or its PAL equivalent) or faster at 1,920x1,080, using H.264 codec in MPEG-4 or QuickTime MOV files. Should have manual controls for shutter and aperture. | | Also look for: | Extensive fast telephoto and high-speed AF lens lineup; simultaneous raw-plus-JPEG capture; excellent vertical-orientation controls; good image histogram; flexible white-balance controls; comprehensive viewfinder information display; comprehensive flash control features; solid battery life |
Documentary, travel, or wildlife photographer I shoot feature magazine assignments, long-term documentary projects, people and activities on the street, or wildlife and other nonlandscape nature subjects. My pictures are printed in high-quality, glossy magazines and books. Or, I make large prints for display in exhibits, at camera club competitions, or on my wall.
| Key Features |
|---|
| Price: | As much as $8,000 for the body | | Resolution: | 12 megapixels or more; preferably full-frame sensor | | Ruggedness: | Metal or hybrid metal/polycarbonate body | | Frame rate: | 5fps or faster | | Burst depth: | 20 shots or more | | AF speed and tracking: | Midlevel to top-notch | | Video: | While you mostly shoot for print, video can come in handy with these types of projects. 30fps (or its PAL equivalent) at 1,920x1,080, using H.264 codec in MPEG-4 or QuickTime MOV files. Should have manual controls for shutter and aperture. | | Also look for: | Simultaneous raw-plus-JPEG capture; excellent vertical orientation controls; tethered-operation capability; solid image histogram; flexible white-balance controls; high-quality raw-conversion software; comprehensive viewfinder information display; comprehensive flash control features; strong battery life; lightweight body and lenses for trekking in the wilderness | Studio, landscape, and fine art photographer I shoot portraits and fashions; products for ads, catalogs, billboards, or eBay; and landscapes, close-ups, abstracts, and other fine-art subjects. My pictures might be shown on the Web, printed in a catalog, or made into a 4x6-foot poster in a clothing store. I make exhibition-quality prints in large sizes, 20x30 inches or bigger.
| Key Features |
|---|
| Price: | As much as $8,000 for the body; you might want to consider medium-format cameras as much as $50,000. | | Resolution: | 12 megapixels minimum; preferably 14 or more; preferably full-frame sensor | | Ruggedness: | All metal or hybrid metal-polycarbonate | | Frame rate: | 3fps or more | | Burst depth: | 6 shots or more | | AF speed and tracking: | Low end to midlevel, depending on typical subjects | | Video: | While you mostly shoot for print, video can come in handy with these types of projects. 30fps (or its PAL equivalent) at 1,920x1,080, using H.264 codec in MPEG-4 or QuickTime MOV files. Should have manual controls for shutter and aperture. | | Also look for: | Tethered operation capability; high-quality raw-conversion software; comprehensive flash-control features; a range of color modes, including new wide-gamut options; flexible exposure bracketing with more than 3 shots |
Wedding and event photographer I shoot weddings, other kinds of parties, and sometimes youth sports team photos. Most of my pictures are printed at 8x10 inches or smaller, but occasionally I need to make a 20x30. I need a fast onsite work flow to help me make sales to friends, relatives, and other partygoers.
| Key Features |
|---|
| Price: | As much as $8,000 for the body | | Resolution: | 12 megapixels or more; preferably full-frame sensor | | Ruggedness: | All metal or hybrid metal-polycarbonate | | Frame rate: | 3fps or more | | Burst depth: | 6 shots, but preferably more | | AF speed and tracking: | Midlevel to top-notch | | Video: | 30fps (or its PAL equivalent) at 1,920x1,080, using H.264 codec in MPEG-4 or QuickTime MOV files. Should have manual controls for shutter and aperture. | | Also look for: | Excellent vertical-orientation controls; tethered operation capability; simultaneous raw-plus-JPEG capture; flexible white-balance controls; compatibility with decent event workflow software; comprehensive flash control features; solid battery life Image files on a digital SLR camera Most standard digicams capture pictures in JPEG format only, but digital SLRs give you more choices. Here's a rundown of four important file formats: JPEG A lossy, compressed file format. Lossy means that actual image data is discarded to increase the compression ratio.
Pros:- Can achieve very large reductions in file size; the resulting smaller files take up less drive and media space and transmit much faster.
- Almost universally supported by imaging programs such as browsers. Sorting, viewing, and cataloging are quick and easy.
Cons:- Produces artifacts and causes loss of detail that may be difficult to notice at low compression ratios but gets progressively worse as compression increases.
- JPEGs are finished RGB images, meaning you have limited capability to alter or reverse the effects of in-camera settings such as white balance, tone curve, or sharpening.
TIFF An uncompressed, finished RGB file format.
Pros:- No quality loss.
- Almost universally supported by imaging programs.
Cons:- Files are many times larger than even low-compression JPEGs.
- TIFFs are finished RGB images, meaning you have limited capability to alter or reverse the effects of in-camera settings such as white balance, tone curve, or sharpening.
Raw The photographer's power tool--it's hard to overemphasize just how powerful they are. Raw files are minimally processed data from the sensor, which you convert to finished RGB images using special software on your computer.
Pros:- Highest potential image quality.
- Depending on your raw-conversion program, you can make extensive changes to image parameters such as & exposure, white balance, tone curve, and sharpening.
- Typically about one-third the size of an RGB TIFF but with none of the information loss of a JPEG.
Cons:- Images are unfinished, so they need to be converted to another format for printing and posting on the Web, which is often a time-consuming process.
- Raw formats are proprietary and usually camera-specific and are often not supported by image editors and other software.
Hint: Think twice about any digital SLR that is not supported by a good raw-conversion program. If the camera's manufacturer doesn't make a decent converter, look for a third-party application. We've counted at least half a dozen for various digital SLR models. And many image-editing apps now include good raw-conversion features for a wide range of popular digital SLRs.
DNG (Adobe Digital Negative) A nonproprietary version of raw that essentially encapsulates the raw sensor data within a TIFF data structure. A few manufacturers, such as Pentax and Samsung, have started supporting DNG in-camera.
Pros:- Image quality on par with raw.
- You can make extensive changes to image parameters such as exposure, white balance, tone curve, and sharpening.
- Typically about one-third the size of an RGB TIFF but with none of the information loss of a JPEG. Files can also be smaller than their raw counterparts.
Cons:- Images are unfinished, so they need to be converted to another format for printing and posting on the Web, which is often a time-consuming process.
- Not yet widely supported in cameras.
About colors The capability to specify your image's color space is a common feature on digital SLRs. What's a color space? In this case, it's a defined range of available colors. The larger the range, the greater the color fidelity and richness your images have. Typically, you can choose between the two color spaces known as sRGB and Adobe RGB. sRGB corresponds well to the set of colors that a typical computer monitor can display. Adobe RGB includes more colors and is a better match for the range of hues produced by the offset printing machinery that is used to make magazines, brochures, posters, and the like.
Some digital SLRs include additional color modes or "looks," which offer different levels of color saturation, color emphasis, and contrast--similar to the varying looks of different films. If you shoot JPEGs and don't have time for a lot of Photoshop tweaking, these color modes can be a handy shortcut to getting the results you like. Most digital SLRs also allow you to create custom color modes by adjusting each of the parameters independently and saving them as a set. What digital SLR accessories do I need? Add-on flash  Sunshine in your camera bag. Good for: Everyone
Unless you're wedded to available-light photography, a good off-camera flash, especially one with a head that can twist, can be invaluable when you've got a borderline exposure situation. It can help eliminate shadows, add catchlights to the subject's eyes in a portrait, and freeze action when you don't want to jack up the shutter speed.
Extra batteries  Always carry a spare. Good for: Everyone, but especially for news and sports, documentary/travel/wildlife, wedding and event photography.
It's a fact: digital cameras suck power, and digital SLRs suck more of it. A key component to good power management is having at least two batteries--one to shoot and one to charge. Having three is better: one to shoot, one fully charged spare on hand, and one in the charger.
Supplemental battery/vertical grip  Grips like this one fit onto the SLR bottom. Good for: News and sports, documentary, magazine/ street/ wildlife, wedding and event photography.
Larger, more expensive digital SLRs typically have a vertical grip with a second shutter release built in for taking vertically oriented shots. Many smaller cameras are compatible with separate vertical grips that incorporate an extra or larger battery.
Filters  Start your collection with a UV filter. Good for: Everyone.
Use UV or skylight filters to protect your lenses, and use polarizers to increase contrast, cut reflections, and deepen the blue of skies. Some filters that were useful with film -- color-correction and colored filters for black-and-white film -- can now be duplicated with digital settings. There are also many special filters available for creating effects such as soft focus, star-shaped flares, and gradients. Many special effects can be applied in image-editing software as well, but some photographers find it more convenient to use a filter instead.
Lens hoods  Block lens flare with a lens hood. Good for: Everyone.
Lens hoods minimize an optical effect called flare, which reduces the contrast and color saturation of your images and can create unintentional light artifacts in your images. No lens should be without a hood, and many come with them.
AC adapters  Most SLRs come with an AC adapter. Good for: Studio/commercial, event photography.
Plug into the wall socket and forget all about exhausted batteries. Some sensor-cleaning methods require an AC adapter because it's a more reliable power source than batteries when you're holding the shutter open for extended periods of time.
Cable releases and remote triggers  Cable releases attach to
compatible shutter-release buttons. Good for: Sports and news, documentary, magazine, wildlife, studio, commercial, event, fine-art photography.
A must-have for pretty much everyone, simple wired cable releases are great when you're using a tripod and want to fire your camera without shaking it. Fancier products, such as the PocketWizard and the Quantum Radio Slave, wirelessly trigger cameras and flashes from hundreds of feet away.
Wi-Fi transmitter  A wireless transmitter typically attaches
to the bottom of the SLR. Good for: Sports and news, event photography, tabletop studio photography.
Though not yet common, many dSLRs from Olympus, Nikon, and Sony now have a transmitter built in. Add-on transmitters are predominantly available for professional Canon and Nikon digital SLRs. They're gadgets that mount to the bottom of the camera and lets you transfer images via either the 802.11b or the 802.11g (Wi-Fi) wireless networking protocol. While you're shooting in the middle of the bar mitzvah, your pictures could be popping up on a computer manned by your assistant at the edge of the banquet hall. He takes lucrative print orders from adoring grandmothers while you keep shooting.
LCD loupe/viewfinder  An LCD hood with a
magnifier lets you shoot video
while holding the camera
up to your eye. Good for: All users shooting video.
The optical viewfinder isn't suited to shooting video, and holding the camera at arms length to view the LCD is both unstable and tiring. These gadgets, known either as LCD loupes or viewfinders, compensate for those inadequacies by allowing you to hold the camera up to your eye and see the complete LCD image.
Video shooting rig  Video shooting rigs
come in a vast array
of designs and configurations. Good for: Documentary, travel, or wildlife photographer; Wedding and event photographer.
dSLRs weren't designed to be used for shooting video, and a whole industry has grown up around kitting cameras out for that purpose. These Frankensteinian rigs come in various modular, user-configurable arrays, with components like LCD loupes, stabilizers, grips, and geared focus knobs.
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| Special--and expensive--glass is used in one or several of the lens elements to counteract an optical defect called chromatic aberration, which can noticeably reduce sharpness, especially in telephoto lenses, and cause color fringing along high-contrast edges. |
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