Sigma SD1 Overview
Preview by Mike Tomkins and Zig Weidelich
Updated: 02/08/2012 - "Merrill" edition
Update, 8 February, 2012: Sigma's announced that they've finally achieved economies of scale for the sensor in the Sigma SD1 that permit them to drop the SD1's price to the level they'd hoped for all along. The drop is dramatic to say the least, with the new Minimum Advertised Price (MAP) coming in at just $2,299. That's quite a drop from the roughly $6,900 the camera was selling for the day before the announcement. We'd felt all along that the camera produced truly exceptional image quality at low ISOs, but the high price made it hard to recommend for all but a fanatical few. With the street price dropping to just $2,299, though, it's a whole different ballgame: This is now a camera that many landscape, architectural, and studio photographers can affordably fall in love with. The natural question is what's to be done for the people who just shelled out $6,900 for a camera that's now worth a third that. The precise details are still cloudy as we go to press, but it appears that Sigma is going to be offering a very generous "points" system whereby current SD1 owners can recoup at least some of the price differential (potentially quite a bit) in the form of other Sigma product. - So it looks like current SD1 owners are in line for a big kit of Sigma lenses for their cameras. (Kudos to Sigma for this level of customer care; we can't recall when a manufacturer has taken such an aggressive approach towards supporting their current users in the face of a price drop.)
One last point: The Sigma SD1 shall henceforth be known as the Sigma SD1 Merrill, in homage to the late co-founder of Foveon and the co-inventor of the Foveon sensor technology Dick Merrill. Despite the name change, there are no changes in the camera's electronics, body, optics, or firmware. (Unlike the fairly radical changes in the DP1 and DP2 Merrill editions.)
The Sigma SD1 is the company's first entry into the high-end DSLR market, and features a magnesium alloy body design that includes rubber o-ring seals on buttons and connectors, for weather and dust resistance. Body dimensions are 5.7" x 4.4" x 3.1" (145.5 mm x 113.5 mm x 80.0 mm) and the body weighs 24.7 ounces or 700 grams without battery and card.
On the inside, the SD1 is based around a newly developed APS-C (23.5 x 15.7mm), Foveon X3, CMOS image sensor. That's quite a bit larger than the sensors used in past Foveon DSLRs, which have been in the region of 20.7 x 13.8mm. The crop factor for the new chip is approximately 1.5x, compared to 1.7x in previous Sigma DSLRs.
The new sensor has a 3:2 aspect ratio, and outputs images with 15.4 megapixel (4,704 x 3,136 pixel) resolution -- a 78% increase in linear resolution as compared to the previous generation Foveon chip used in Sigma's SD15 DSLR. As with all Foveon sensors, full color information is recorded at every pixel location, with the new chip including a total of just over 46 million effective photodiodes. Helping per-pixel sharpness further, Sigma doesn't use an optical low-pass filter in the Sigma SD1, since without a Bayer filter, color moire isn't an issue. (Of course, luminance moire is still possible with an X3 sensor.) To handle all the extra data, the SD1 is said to include a pair of TRUE II ("Three-layer Responsive Ultimate Engine") image processors, the same type used in the SD15, although that camera only needed one such processor. With dual processors and DDR3 SDRAM buffer memory, the SD1 is capable of full-resolution bursts of up to 5 frames per second for 7 RAW frames, and can record RAW and JPEG files simultaneously, a first for Sigma cameras.
On its front panel, the SD1 sports a Sigma SA bayonet lens mount compatible with more than 40 Sigma SA mount lenses. To assist in focusing, Sigma has specified a new 11-point, twin cross-type, phase detection autofocus sensor, rated at a working range of EV -1 to 18 at ISO 100. Focus modes include both single, and continuous with predictive capability. AF points can be selected both automatically and manually. Depth of field preview is available courtesy of a dedicated button.
For framing images, the Sigma SD1 offers up a pentaprism viewfinder with 98% coverage, and 0.95x magnification. The SD1's finder has an 18mm eye point, and provides -3 to +1.5 diopter correction. The SD1 viewfinder has a fixed matte screen, and provides a superimposed AF point display. On the rear panel, there's a 3.0-inch, 460,000 dot LCD panel with a wide viewing angle for reviewing captured images.
The Sigma SD1 also provides a built-in, manual popup flash strobe with a guide number of 11m, and 17mm coverage. There's also both a PC sync terminal, and a hot shoe for external strobes, compatible with the EM-140DG, EF-610 DG ST, and EF-610 DG SUPER flash guns. X-sync is at 1/180 second, and flash exposures are determined with Sigma's S-TTL metering system. +/- 3.0EV of flash exposure compensation is available, in 1/3 EV steps.
Designed for professionals and serious enthusiasts, the Sigma SD1's exposure options do not include any Scene modes, offering only Program AE (with Program Shift), Aperture Priority AE, Shutter Priority AE and Manual modes, though the exposure mode dial does offer three custom settings for quick recall. The Sigma SD1's exposure system features four metering modes: 77-segment Evaluative, Center Area, Center-Weighted Average and Spot metering with a working range of 1 EV to 20 EV (50mm f/1.4 lens at ISO 100). ISO sensitivity ranges from 100 to 6,400 equivalents and shutter speeds are available from 1/8000 to 30 seconds including a bulb mode that can be extended up to two minutes.
The Sigma SD1 stores images on Type-I CompactFlash cards, and its CF slot is UDMA compatible. It doesn't support Type-II cards, such as Microdrive. Power is derived from a proprietary BP-21 Lithium-ion battery pack, or from an optional PG-31 Power Grip which can hold two BP-21 battery packs. No word on battery life.
The Sigma SD1 does not offer any live view or movie recording capabilities. Still, the Sigma SD1 looks like a huge step forward for the company's unique Foveon-based DSLR lineup, and will likely prove of great interest to fans of X3 sensors.
As of February 8, 2011, the minimum advertised price (MAP; effectively the "street" price) for the Sigma SD1 has been reduced to US$2,299; basically a third of what it was selling for before that point. In an unusual move, Sigma has announced that they'll be providing compensation for prior SD1 owners in the form of "points" that can be redeemed for other Sigma products. Precise details of the points system weren't available at the time of announcement; we'll hopefully be able to come back and update this information soon, once it's available.