Boasting a resolution three times the size of its predecessor, the SD1’s 46 megapixels take it into medium format territory. But, as ever with Sigma cameras, that’s just half the story, says Richard Kilpatrick

It’s almost a decade since Sigma’s first digital camera burst onto the market. And, just as Sigma announced its entry into the burgeoning digital SLR arena, in a perfectly timed act of public relations, Foveon, the California-based technology firm and CMOS pioneer, announced its revolutionary X3 sensor. The SD9 was uniquely talented, thanks to its “three layer” Foveon X3 sensor, and a bit of a bargain with a launch price of £1299 – pretty much set to compete with the Canon EOS D60, while the Nikon D100 was almost twice the price.

Three models followed, but the upgrades failed to keep up with the competition, relying on Foveon’s pace of development. So, while 16-18 megapixels became the industry norm, Sigma’s cameras were stuck with a 4.5-megapixel sensor – and the job of explaining why this figure should be multiplied by three to take into account the X3’s separate photosites for RGB capture. So, after Sigma also introduced a groundbreaking digital compact camera using the X3 technology, it bought Foveon in 2008 and focused development on a truly competitive DSLR sensor.

Revealed at Photokina 2010, and on sale since June, the SD1 boasts a headline 46-megapixel capture – an attention-grabbing number that translates into a 15.4-megapixel APS-C sensor of 23.5×15.7mm, with a 5.0µm pixel pitch (up from 20.7×13.8mm/7.8µm), multiplied by the three RGB photodiode layers. While the technology has improved since the previous models, the resolution confusion of Sigma’s cameras remains; the most common theory puts the equivalent Bayer CFA sensor at 30 megapixels. But there has always been more to Foveon’s technology than the resolution suggests. The primary factor is the lack of colour interpolation, which allows the sensor to work without a low-pass filter without risking colour Moiré. At a pixel level, whether it’s an SD15, DP-series or SD1, the images are crisp and pure, but with the SD1, native output files are now usable for large prints without upsizing – and so the SD1 may be the first Sigma camera since the SD9 that can be fairly weighed up against contemporary DSLRs.

That is until you look at the pricing. The SD1 has a recommended price of £6199, so even with street prices pushing that down closer to £5500, it remains one of the most expensive DSLRs on the market. For many of the enthusiasts who buy Sigma’s cameras, that’s an unattainable goal, and a long way off the sub-£2000 price that was rumoured last year.

LESS IS MORE?

The matter in hand, though, is the magnesium-alloy-bodied SD1. And hands are a good place for it to be – I’ve held few cameras that fit as comfortably. The button layout is simple; they are all clearly labelled with few multiple functions and none of them double-up during camera operation. As with the DP1 to DP2 changes, Sigma is applying lessons learned from customer feedback to subsequent designs. The most frequent adjustments of exposure compensation and AF point selection are a thumb-and-forefinger movement that avoids placing your grip on the camera at risk, while less frequently altered settings can be selected via the QS button and four-way selector.

This simplicity helps make the SD1 an extremely intuitive camera, and rapid in operation as a result. The viewfinder is average for the form factor, with 98 percent coverage and 0.95× magnification, a rotary diopter adjustment replacing the rather easy-to-use (and knock out of place) slider of the SD15, and a useful but basic LCD information strip. The AF points are illuminated and there is a centre target, but there is no grid available either as an accessory or a switchable option. The focusing screen is good, and with appropriately fast lenses you get a pleasing “snap” of texture and Moiré reminiscent of larger-format systems. Still, I’d like to see a grid option, and perhaps a return of the split-image or microprism focusing aids that have long fallen out of favour in mainstream cameras.

The specifications are appropriate – if not class leading – to a higher-end body with 1/8000s shutter, two-minute exposure (in Extended mode), 11-point AF and 77-segment metering. Externally there are infra-red and wired remote ports, a PC Sync socket for flash sync of 1/180s, and USB/power connections. The dedicated accessory flashgun (EF-610 DG Super) offers High-Speed FP Sync up to 1/8000s, rear-curtain sync, and all the DG-Super models can be wirelessly controlled by the camera. There is a little GN11 pop-up flash with 17mm coverage, which rises to a useful height from the prism.

Low-cost, high-volume cameras have muddied the expectations for a DSLR, so the SD1’s basic feature set can come as a shock to anyone used to extensive in-camera effects, or HD video, in every body. The LCD screen on the SD1 is 3.0-inch, 480×320 (Half VGA), with a tough-looking cover; the smooth back doesn’t appear to offer mounting points for a clip-on protector. Connectivity is one of the weaker aspects of the SD1, as there is no HDMI playback, the USB port doesn’t allow tethering, and the flash sync is limited in control and requires the entire cover to be moved to access the socket. Admittedly, even entry-level studio flash such as the D-Lite IT comes with a wireless trigger now, but compared to the screw-in cover on the SD15 this seems like a retrograde step.

The digital side of things is revolutionary, yet so thoroughly obvious a step in evolution it doesn’t feel alien. Sigma adopters from 2002 were treated to a double-take moment when they inspected their files; the output here is a lot more of the same pixel-level clarity and remarkable retention of highlight detail. However, the technical accomplishment within is stunning – this is no weighty beast of a camera full of heatsinks and electronics. Yet it carries two Milbeaut-based True-II image processors and DDR-3 buffer memory, allowing it to handle 46 megapixels of raw data. Lossless 12-bit/channel output yields 56MB files with tolerable shooting speeds; by comparison a Nikon D3x writing a similar format is only 28MB. Throwing more confusion into the numbers, the Sigma’s 12 bits are not per spatial pixel, but per photosite (each pixel containing three). Suffice to say that, as always, the SD1’s technology remains complex to compare at a technical level, but astoundingly easy as a finished file.

PERFORMANCE

While still lagging behind the headline (and often severely noise-reduced at source on the smaller sensors) high ISO figures claimed by many cameras, the SD1 has a specified range of 100-6400. Realistically, 6400 is unusable except for very well lit, bright subjects, and 3200 shows a tendency to blotchy noise structures, while 100-800 is impressive, and 1600 usable. The SD tends to easily control luminance noise up to the point where a coarse green structure affects the shadows at ISO 3200.

As a solution for getting ultimate image quality from a 15-megapixel capture, no other DSLR system comes close; the final photograph produced by the SD1 is unmatched. Gradation, colour balance and resolved detail are all exceptional. Given the number of photographers working with 12-megapixel Bayer cameras – shooting, cropping and upsizing an image for output – the SD1 addresses that market’s needs perfectly. A lack of colour artifacts and aliasing makes clean resizing simple, though the flipside to this critically sharp sensor is that it’s extremely unforgiving; lens issues, camera shake, back- or front-focus will be thrown into sharp (or otherwise) relief. To that end, Sigma has added AF Micro Adjustment to the SD1’s functions – they’re easy to use and simply matched to that model of lens.

In terms of burst performance, a maximum 7fps (albeit in the low-resolution, JPEG mode, which for many users would defeat the purpose of using the SD1) may serve in an emergency. The real-world performance is represented by the raw+JPEG files, with a seven-frame buffer and about 3.5fps; write delays after that are 4s for the first frame, 10-13s for a single frame, and about 75s to fully clear the buffer. Some colour profiles are offered for JPEG, which also affect the raw preview.

For most photographers, this performance should be more than enough – if you want to reel off action sequences or capture celebrities, then there are cameras on the market with those specialist functions (though it’s becoming common to have 5fps at a good resolution). The low-resolution (2336×1568 multiplied by three) is a usable 3.6-megapixel file. Surprisingly from Variable Pixel Size (or “binning”) pioneers, there appears to be only a slight improvement in noise at higher ISO on the smaller files, but if shooting speed is more important than file size the SD1 does offer a solution.

INFRA-RED CAPABILITIES

Another group of specialists may find the SD1 particularly compelling because, as with the previous Sigma DSLRs, the sensor is almost wholly exposed behind the shutter without a low pass/IR filter. To cut infra-red light and minimise sensor dust, the hot mirror is in the form of a user-removable protector behind the lens mount. This unclips, and with the addition of an R72 filter, a Sigma DSLR becomes a sharp, uninterpolated infra-red camera. Using an SD for this is incredibly straightforward, as the AF sensor deprived of visible light focuses using infra-red. The metering is a different matter, so manual settings are appropriate; for framing you can either remove the R72 filter and select the focus point while composing, or use an external viewfinder – I use a simple wireframe “Ikodot”. For mixed IR-and-visible light it’s necessary to adjust focus (AF micro adjustment can sometimes cover this), as few lenses retain an IR-index mark.

Sigma Photo Pro is bundled as a raw processor for the X3F files. Now at version 5, it’s been reskinned and improved, but still remains extremely basic, with a limited range of adjustments. Typically, third-party raw processors such as Adobe Camera Raw gain support for new Sigmas around a month after release, so as you are reading this, Lightroom/Bridge support may be available. Aperture has never supported X3F files, though a Mac OS plug-in allows preview in Finder.

CONCLUSIONS

For archival purposes it may find a niche where medium format is seen as overkill: on a good copy stand and with appropriate lenses it will capture detail only possible with multi-shot backs costing considerably more. It’s an ideal portrait and fashion camera that gives the handling (and weight, crucially) of a small DSLR, natural colours and no risk of colour Moiré in hair and fabric – something even medium format systems suffer.

Sigma’s lens range is going to come under serious scrutiny from its flagship camera, and the increases in price and quality of newer releases hint at a range being developed to match the expectations – at the time of writing this review, the 150mm OS Macro was yet to ship in SA mount. Priced as it is, Sigma would do well to encourage availability of the camera through rental outlets.

Technical superiority is rarely a guarantee of success in the marketplace; Sigma’s camera development, to the observer, seems to demonstrate a solipsistic brilliance that contributes to the unique nature of the product as founder Michihiro Yamaki works towards his long-term vision. The SD9 brought serious DSLRs closer to a three-figure price point in the UK and the DP was a true trendsetter – just look at the range of premium APS-C compacts now offered. Focus groups and marketing committees would long have concluded the SD1 shouldn’t exist – cost projections giving that final price would have seen development cease. Sigma is taking a big risk, offering something new without the safety net of undercutting the nearest competition. But if image quality matters more than anything else to you as a photographer, the SD1’s price is less relevant than the fact that the camera exists at all.

We hope you enjoyed this article from the British Journal of Photography for iPad, Issue One. For more information on how to get this free app, which includes all the photos from this article plus hundreds more, click here.