Sensor and sensitivity
The Foveon X3 sensor is both this dSLR's main selling point and its Achilles heel. Sigma claims its triple-layered composition -- one silicon-embedded layer of photo detectors each for red, green and blue -- delivers more accurate colour reproduction, and, therefore, more life-like results.
That's a big claim, especially since, when you open up a fine-compression-level JPEG in Photoshop, the actual pixel count is closer to a mere 4.6 megapixels (the headline resolution divided by three -- one for each of those aforementioned layers).
The camera costs around £800 for the body only, and adding the two lenses that we had in for testing, a 24-70mm f/2.8 macro and stabilised 70-300mm f/4-5.6 zoom lens, will bring the total to nearly £1,600. That will leave some people feeling distinctly short-changed.
The SD15's battery life is good for around 500 shots, which is what we'd expect at this level. Light-sensitivity settings stretch from ISO 100 up to ISO 1,600, which feels modest. They can, however, be 'extended', via the camera's menus, to an equivalent ISO 50 and ISO 3,200. You might wish you hadn't bothered, though, as, over ISO 800, the results from the SD15 are alarmingly noisy.
The camera comes into its own when photographing still-life arrangements, portraits and nature scenes in better light. The subtleties of differing colour tones are then brought to the fore, and will almost certainly please fine-art photographers.
The Sigma SD15 couldn't be described as a good-value all-round dSLR. If that's what you're in the market for, then look elsewhere -- at theto give but one example. Ultimately, the SD15 is a specialist tool that seems to lack a clear identity.
Edited by Charles Kloet