Tips for Buying a Digital SLR Camera

 
There’s a definite visceral reaction when taking pictures with an SLR.
The look of the camera and the way it seems to be an extension of my hand often evokes a sense that something wonderful is only a fraction of a second away. Although I’ve taken great photographs with a compact digital camera, a digital SLR provides the features and controls I often need to ensure I come away with the photograph I expect.

Despite the emotions D-SLRs evoke, what really matters are the pictures it produces. Today’s interchangeable-lens cameras offer a host of features that seem to make anything possible. From high-res sensors to wireless flash systems, these cameras are pushing what ís possible with photography, digital or not. Here’s a look at what to look for when you compare digital SLR cameras.

Sensor And Resolution
Since the first digital camera broke the 1-megapixel barrier not so long ago, the question of a camera’s resolution always seems to be the measuring stick by which all newcomers are gauged. Although there’s more to a quality photograph than a camera’s pixel count, resolution still is important to consider.

The 16.7-megapixel Canon EOS-1Ds Mark II and 12.4-megapixel Nikon D2xs produce large image files whose quality many say rivals that produced on medium-format film. The large files delivered by these cameras translate to quality 16x20-inch and larger prints with retention of detail, even when aggressively cropped.

Even moderately priced D-SLRs deliver enough resolution for excellent 13x19-inch prints. Entry-level cameras offer approximately 6-megapixel resolution, making quality enlargements both possible and affordable. For a boost in resolution, the next level includes 8 to 10 megapixels.

Regardless of your preference in resolution, all of these cameras produce enlargements that are comparable to anything created on 35mm film.

APS ANd Full-Frame Sensors
Photographers who use 35mm lenses immediately notice the difference in magnification that occurs when those lenses are mounted on a D-SLR. This is because most D-SLR sensors are smaller than a standard 35mm frame. Named after a film format released in the ’90s, an APS-size sensor measures approximately 15x23mm. Because the light from the rear of the lens is covering a smaller surface area, the lens delivers an image that looks as if it was taken with a longer focal length.

The lens magnification factor, which often ranges between 1.3x and 1.6x, increases the effective focal length of an attached lens. A 300mm lens, when mounted on a camera with a lens magnification factor of 1.5x, will perform as a 450mm. This occurs with no loss of light as would be experienced with the use of a teleconverter. For photographers who prefer to use their existing lenses at their “true” focal length, however, the Canon EOS-1Ds Mark II and EOS 5D are full-frame digital SLRs whose sensors have the same dimensions of a 35mm frame.

Nikon takes advantage of this lens magnification factor in the High Speed Crop (HSC) mode of its D2xs camera. The 12.4-megapixel camera normally features a 1.5x magnification factor, but in HSC mode, the camera’s resolution is reduced to 6.8 megapixels. By using a smaller area of the CMOS sensor, lens magnification increases by 2x, making a 300mm ƒ/2.8 lens into a 600mm.

Olympus has based its cameras on an entirely new system. Using a Four Thirds sensor, Olympus SLRs allow for the creation of optics that have been specifically designed for digital image capture. In addition to being lighter and more compact than comparable focal lengths, these lenses also promise improved color and tonal rendition while delivering excellent sharpness.

---

Image Processing
When light passes through the lens and hits the camera’s CCD or CMOS sensor, an image isn’t instantly created. Instead, the analog data produced by the light hitting the sensor is converted to digital using an analog-to-digital converter (ADC). The ability for the ADC to transform light to digital is the first critical step for a quality image.

The next step occurs when the on-board processor interprets that data and enhances the image file. Whether it’s known as Canon DIGIC II, Olympus TruePic technology or something else, the camera takes the raw data and evaluates it for color, white balance, sharpness, tonality, contrast and color space. It’s this processing of the image that can result in the distinct look produced by an individual SLR.

Although shooting in RAW leaves all this control in the hands of the photographer, the camera’s on-board processing can nevertheless greatly impact your digital images.

ISO Sensitivity And Noise
Until recently, one of the significant advantages of film was its ability to deliver usable images at high ISO settings. With digital cameras, ISO settings of 800 and higher often resulted in excessive noise—multicolored specks that appeared in the frame. Especially obvious in areas with shadow detail, noise also could be found in areas of uniform color, such as sky or skin. The prevalence of noise would be a real distraction with enlargements.

Improvement in the manufacturing of image sensors along with the camera’s built-in software has dramatically reduced the presence of noise at ISO settings as high as 1600. For photographers who shoot under low-light conditions or shoot long exposures, this improvement has been both anticipated and appreciated.

Performance And Speed
Speed and accuracy are the hallmarks of the autofocus systems found in current digital SLRs. Multi-sensor AF modules provide photographers with the ability to make off-center compositions with ease and precision, even under low-light conditions. And for fast-moving subjects, these systems, combined with a high frames-per-second burst rate, deliver a sequence of sharp images of even the speediest subjects.

All this means nothing if the camera doesn’t take a picture when you want it to. Compact cameras often have frustrated users with shutter lag—the delay between pressing the shutter release button and the actual image being captured. Digital SLRs now offer a response time that’s equal to or better than that of a traditional SLR.

Features And Specifications
Although resolution and price can be the focus of a camera, each digital SLR brings its own uniqueness to the table. Some systems offer program modes designed for specific types of photography, such as landscape, portraits or action. These scene-specific exposure modes not only bias shutter speed and aperture, but also impact contrast, noise reduction and depth of field. Features such as wireless control of flash and downloading of files from camera to computer are ways that are increasing versatility and creating unique niches in this competitive market.

It all comes down to what kind of photograph you want to create and discovering which of these tools will do the job for you. With a wide range of choices, the right camera is closer than you might think.