Home Cameras SLRs D-SLR's: State Of The Art, Part II
Tuesday, February 3, 2009

D-SLR State Of The Art, Part II

What to know about the latest digital sensors, ISO and image quality

This Article Features Photo Zoom


dslrsDxO Labs has introduced a useful new website, DxOMark.com. The free service reports the results of their testing of the sensor performance of many D-SLRs and a few compact digital cameras.

DxO is known to most photographers as the producer of the excellent DxO Optics Pro software, which provides many useful features, including converting RAW images. But DxO began (and continues) as the producer of DxO Analyzer, a turn-key, image-quality management laboratory widely used by the imaging industry. They’re now revealing to all the results of their analyses of RAW image-sensor performance.

Basically, they evaluate digital camera sensor performance in three areas: color depth (important to portrait photographers), dynamic range (important to landscape shooters) and low-light ISO performance (of great interest to action and low-light shooters).

Bear in mind that, as DxO points out, RAW sensor performance is just one thing to consider when choosing a D-SLR. In-camera image processing, autofocusing performance, speed of operation, range and quality of lenses available and more are also important. But DxOMark is one more valuable tool to assist you in evaluating potential camera purchases.

Today’s D-SLRs can produce terrific images. Even so, there are some things you can do to maximize image quality:
1. Shoot RAW format.
2. Use the sensor’s native ISO, the lowest one in the “normal” (nonexpanded) ISO range, whenever possible.
3. If you have to use a higher ISO, use the lowest one that will let you get the shot.
4. Nail the exposure. Overexposure blows out bright areas; underexposure increases noise tremendously.
5. Use noise-reduction software (best) or the camera’s noise-reduction features when shooting at higher ISO settings.

More Than Just The Sensor
A number of D-SLRs use similar sensors, both within a manufacturer’s line (the Canon EOS-1Ds Mark III and EOS 5D Mark II, and the Nikon D3 and D700, for example) and across manufacturers’ lines (the Pentax K20D and Samsung GX-20, and the Nikon D3X and Sony A900, for example). But the images produced by the cameras are different. Why? In part because the sensors aren’t exactly the same: The EOS 5D Mark II’s has a new RGB filter and other improvements, for example, while the D3X’s sensor provides Live View functions that the Sony A900’s does not. dslrs

Higher ISO Or Longer Exposure?
dslrsdslrsHigher ISO settings increase noise, and longer exposure times increase noise. In dim light, is it better to shoot at a higher ISO with shorter exposure time or at a lower ISO with a longer exposure time?

Well, if you need a particular shutter speed—a fast one to freeze action or a slow one to blur it—then you have your answer. But if a particular shutter speed isn’t required for pictorial purposes, you’ll probably get better results using longer exposure times and lower ISO settings. Test your camera to see what happens to image quality at higher ISOs and at longer exposure times. Perhaps a compromise is best: a moderate ISO setting and a moderate shutter speed. In any event, try to nail the exposure. Underexposure increases noise greatly and is death at higher ISOs.


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