Sigma SD15 £790
13th Sep 2010 | 09:00
Sigma's Foveon X3 sensor design is unique, but does the SD 15 move it any further forward?
Sigma's best known for its lenses, but it also produces two very interesting cameras. One is the DP1s/DP2s compact (same camera, different lenses) and the other is the SD series of D-SLRs.
First came the 3Mp SD9 in 2002, which was followed by an improved SD10 in 2003, and then by the 4.7Mp SD14 in 2007. The SD15 is a development of the SD14, but at its heart is the same Foveon X3 sensor.
But while other makers bring out new sensors every couple of years, Sigma's Foveon X3 technology moves more slowly. As a result, the SD15 is more of a redesign than a new camera, despite the fact that it's been three years since the SD14 hit the market.
The Foveon X3's low pixel count sounds unimpressive these days, but the figures are misleading. Because of the way the images are created, and the high levels of sharpness they display, the SD15 is a pretty good match for any other APS-C D-SLR. But even if it is as good as any other SLR, why buy the SD15?
First, the extreme sharpness of the images gives them a visual quality you don't get with other cameras, even if the resolution is lower. Second, 4.7Mp files take up a lot less space than 12-14Mp images. Third, the SD15 uses a traditional design that offers refreshing simplicity, and if you already know your way around a camera, it's nice not to have to negotiate layers of gadgets and automation to get to key controls.
The SD15 is only a modest upgrade from the SD14, but it now uses SD/SDHC memory cards and has a 100,000-cycle shutter mechanism and a good-quality 460,000-dot LCD display. And like other Sigma cameras, it comes with Sigma's Photo Pro RAW conversion software.
You can open and convert its files with Adobe Camera Raw, but the Sigma software is better-tuned to the camera's own colour modes, and gives rather better performance at high ISOs.
Build quality and handling
You immediately notice the SD15's heavy, slab-like body. It feels tough and durable, but the plastic finish feels like it belongs on a cheaper body. There are some neat design touches, though.
There's a mirror lock-up mode for cutting shake with macro shots and extreme telephoto lenses, and inside the lens throat there's a glass Dust Protector designed to prevent dust getting into the mirror box and on to the sensor.
The controls are a little patchy. Some are very good, such as the main mode dial, which has just four positions for the camera's Program, Aperture Priority, Shutter Priority and Manual exposure modes. There's no idiot-proof auto mode, no scene modes and no movie mode.
On the left-hand side of the pentaprism is another dial, this time for setting the drive mode. Again, it's plain, straightforward and simple.
On the top of the grip on the right-hand side is a single control dial. It's a mild disappointment that there's only one, and it means that in Manual mode you have to hold down the exposure compensation button to toggle between shutter speed and aperture adjustment. Most SLRs in this price bracket have two dials.
This control dial has quite a heavy action, too, and it would have been better if it had overhung the front of the camera because it would be easier to get a proper grip on it.
Controls and Features
There are a couple of issues on the back of the camera, too. There's a cluster of buttons at the top right for altering the ISO, metering and focus point, but these are a little too easy to press by accident if you rest your thumb in the wrong place. In addition, the functions of some of the buttons aren't clear.
There's a red 'asterisk' button alongside the LCD, which is used in playback mode for marking, rotating or locking images – building this into the main menus would be simpler. Plus, there's a Cancel button below the navipad on the right with no immediately obvious purpose, since you can cancel your way out of menus using the Menu button.
There's more than one way to change camera settings, too. The Quick Set button is in charge of the photo style (Standard, Vivid, Neutral, Portrait, Landscape), file format (RAW or JPEG), white balance and image quality (if you're shooting JPEGs). But there's also a Func button, which lets you select the flash and AF mode.
This button also displays a focus grid showing you the currently selected AF point, plus sundry other camera settings including the exposure mode, ISO, shutter speed and aperture. And yet this isn't the information display itself. This is another screen, showing some of the same information, which is activated by the 'i' button alongside the LCD. Frankly, it's a bit of a mess.
There's not much to say about the SD15's features that hasn't been said already. There's no movie mode, Live View or special scene modes to talk about. The 3fps continuous shooting speed is only adequate for a camera in this price range, although it can keep it up for 21 RAW frames in succession.
The 500-shot battery life is, again, adequate without being exceptional, as is the 77-segment auto-exposure sensor, which links the exposure to the currently selected focus point. You do get four metering modes, though, including Centre Area mode, which acts like a large 'spot' mode and is similar to the Partial mode you get on some Canon cameras.
So do the SD15's sophisticated metering options help its overall performance? Not exactly.
The standard multi-pattern metering mode proved distinctly unpredictable, especially with high-contrast subjects. A slight difference in viewpoint could produce big differences in exposure, possibly because of the shift in focus point and hence the way the meter reacted to the 'new' subject.
Otherwise, though, the SD15 is very impressive. If you haven't seen what the Foveon sensor can do, you'll be amazed at the clarity of the fine detail it produces. Each pixel is razor sharp. The 17-70mm Sigma lens supplied for this review proved rather good, too, with low levels of distortion, little chromatic aberration and terrific edge-to-edge sharpness.
This camera can't shoot RAW and JPEG files simultaneously, so it's likely most users will choose to shoot RAW. The conversions created by the Sigma Photo Pro software are rich, contrasty and highly saturated – perhaps a little too saturated now and again if you use the Sigma Photo Pro software's automatic setting.
You can also adjust the exposure, colour, white balance and other settings manually, or use the original camera settings. This gives more consistent results, even if it involves a little more work. At low ISOs there's no significant noise at all, but it does increase rapidly as the ISOs go up. This is one area where the SD15 does lag behind conventional D-SLRs.
Having said that, the conversions produced by the Sigma Photo Pro software from ISO1600 originals aren't at all bad, and you can trade off noise against smoothing to get a balance you're comfortable with.
Some might see the Foveon X3 sensor as the SD15's weak point, but it isn't. It produces small files, true, but they have such astonishing clarity and sharpness that they're a fair match for any regular APS-C format D-SLR.
The lack of features isn't really a problem, either. Using a D-SLR that's been stripped down to its basics will be a refreshing experience for experienced photographers who favour a thinking, methodical approach rather than complicated high-tech automation.
Where the SD15 does fall down is in the most mundane, straightforward areas of design and usability. It's big and tough, but also feels rather crude. And the controls are too muddled and confused: it's a simple camera that's been made unnecessarily frustrating.
And that's a shame. It's great to see such an innovative approach to digital imaging, and the quality of the Foveon X3 sensor's images is remarkable. We can only imagine what could be achieved if it could be developed into larger, higher-resolution versions.
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