A Viewfinder Darkly

Photography tips and tutorials

Sigma SD1 Digital SLR with the Foveon Sensor

May 26 2011

by Philip Northeast

Sigma’s new SD1 with its unconventional 46 megapixel Foveon digital sensor, housed in a conventional DSLR body, is set to ship in June with a price in the US of just under $7,000.

Sigma SD1

Sigma SD1

The Foveon Sensor

Unlike digital sensors found in other brands of cameras Sigma’s Foveon sensor arranges its light collecting points vertically.   Sigma says this three layer approach takes advantage of  silicon’s characteristic, the basic material of digital sensors, to absorb light at different depths for different wavelengths, or colours. All digital sensors split light up into its three primary components, the basic Red, Green, and Blue (RGB) colors. The luminosity of Red, Green or Blue light at any point varies depending upon the original color of the light reaching the sensor.

In the Foveon digital sensor the shorter wavelength blue light is absorbed nearest the surface, while longest wavelength red light is absorbed deepest into the sensor, with green light in between. This means the Faveon sensor collects the RGB light information used to construct a digital image a pixel at one spot.

Conventional digital sensors collect light information for each primary color at a separate pixel point. The light  sensitive parts of a conventional digital sensor do not see color directly, they only measure light intensity. Each sensor, or pixel, has a filter to allow only Red , Green or Blue light into the pixel.  This RGB data from the sensor is then processed to create the digital image, either in camera to create a jpeg file, or stored as RAW file and the recombination is done by RAW converter software on a computer.  All manufacturers count these primary color pixels in their specifications rather than the final combined pixel.

Because they count and process pixel information in different ways comparing the resolution of the Foveon sensor with conventional digital sensors is difficult. Even though SD1’s Foveon sensor has the physical dimensions of 15 megapixel an APS-C digital sensor, the mathematical equivalent resolution is about 46 megapixels. According to Sigma the Foveon sensor in the SD1 has a 30 megapixel equivalent emotional image quality.

The real comparison will come when photographers start using the Sigma SD1 and the pictures can be judged.

The SD1 Camera Body

Because of t he unique digital sensor technology the Sigma SD1 is intended to be a high resolution APS-C size camera aimed at the high end of the market. The resolution and pricing   means it competes with the best DSLRs from Nikon and Canon as well as the more affordable medium format digital cameras from Leica and Pentax.

The SD1’s body has the basic features photographers expect of a high end camera such as a solid yet lightweight magnesium alloy body with weather sealing making it dust and moisture resistant. The SD1 uses Compact Flash cards normally found in high end professional cameras. There are no scene modes to be found, only the usual exposure modes as this camera is aimed at photographers.


Key Specs


Sigma Lenses

Sigma are celebrating fifty years of making lenses for other manufacturer’s cameras. While they are relatively new to manufacturing  their own cameras, they do have long history in the photographic industry.  Sigma does have a reputation as producers of cheaper lenses, but they do make mid price lenses and professional quality EX lenses.


The price of the Sigma SD1 seems to be a matter of some confusion.  Some media outlets reported a Sigma press release giving a  body only price of $US 9,700.  A major New York camera shop has them listed at under $US 7,000 for a body only.  On the Sigma America site there are SD1 kits available for pre-order in the $US 7,000 to $US 8,000 range depending on the lens kits chosen.



Sigma SD1 Specification


Format Interchangeable lens SLR camera
Storage Media Compact Flash (Type I, UDMA compatible)
Image Sensor Size 23.5×15.7mm
Lens Mount SIGMA SA bayonet mount
Compatible Lenses SIGMA SA mount interchangeable lenses
Angle of View Equivalent to approx. 1.5 times the focal length of the lens (for 35mm cameras)
Image Sensor X3 direct image sensor (CMOS)
Pixels Total Pixels 48MP, Effective Pixels 46MP (4,800×3,200×3 layers)
Aspect Ratio 03:02
Still Image Format Exif 2.3, DCF 2.0
Recording Mode Lossless compression RAW data(12-bit, High, Medium, Low), JPEG(High, Medium, Low)
Capture File Size RAW
High Approx. 45 MB (4,704×3,136×3)
Medium  Approx.24 MB (3,264×2,176×3)
Low Approx. 12 MB (2,336×1,568×3)JPEG
Fine Approx.  10 MB (4,704×3,136)
Normal Approx. 5.6 MB (4,704×3,136)
Basic  Approx. 4.2 MB (4,704×3,136)

Fine Approx. 5 MB (3,264×2,176)
Normal  Approx. 2.7 MB (3,264×2,176)
Basic  Approx. 2 MB (3,264×2,176)

Fine Approx. 2.5 MB (2,336×1,568)
Normal Approx. 1.4 MB (2,336×1,568)
Basic Approx. 1 MB (2,336×1,568)Continuous shooting speedHigh?5 frame/sec., Medium?6 frame/sec., Low?6 frame/sec.Continuous bufferHigh?Max. 7 frames, Medium?Max. 14 frames, Low?Max. 14 framesInterfaceUSB(USB2.0), Video Out (NTSC/PAL)White Balance8 types (Auto, Daylight, Shade, Overcast, Incandescent, Fluorescent, Flash and Custom)Color Mode7 types (Standard, Vivid, Neutral, Portrait, Landscape, B&W, Sepia)Viewfinder TypPentaprism SLR viewfinderViewfinder Frame Coverage98% vertical, 98% horizontalViewfinder Magnification0.95x (50mmF1.4 – ?)Eye point18mmDiopter Adjustment Range-3.0 dpt – +1.5 dptAuto Focus TypeTTL phase difference detection systemAF Point11 points twin cross sensorAF Operating RangeEV -1 to +18 (ISO100)Focus ModeSingle AF, Continuous AF (with AF motion prediction function), ManualAF Point SelectionAutomatic Selection, Manual SelectionMetering Systems77 segment Evaluative Metering, Spot Metering, Center Area Metering, Center-Weighted Average MeteringMetering RangeEV 1 to 20 (50mm F1.4 : ISO100)Exposure Control System[P] Program AE (Program Shift is possible),[S] Shutter Speed Priority AE,[A] Aperture Priority AE, [M] ManualISO SensitivityISO100,200,400,800,1600,3200,6400Exposure Compensation±3 EV (in 1/3 stop increments)Auto BracketingThree or Five frames (in 1/3 steps, Appropriate Exposure-Under Exposure-Over Exposure)Shutter TypeElectronically Controlled Focal Plane ShutterShutter Speed1/8000 – 30 sec.,Bulb (up to 30 sec. With Extended Mode: 2 min.)Flash ConnectivityHot shoe (contact X synchronization at 1/180 sec. or less, with dedicated flash linking contact)Built-in FlashManual Pop-up Built-in flash, GN11 (17mm lens angle covered)LCD MonitorType : TFT color LCD monitor, Monitor Size : 3.0″, LCD Pixels : Approx. 460,000Reviewing ImagesSingle frame display, Multi display [9 frames],Zoom, Slide ShowLCD Monitor LanguageEnglish / Japanese / German / French / Spanish /Italian / Chinese (Simplified) / Korean / RussianPowerLi-ion Battery Pack BP-21, Batterry Chager BC-21,AC Adapter SAC-4 (optional)Dimensions145.5 mm/5.7″ (W) × 113.5 mm/4.4″(H) × 80.0 mm/3.1Weight700g/24.7oz. (without battery and card)SD1 Accessories.Li-ion Battery BP-21 .Battery Charger BC-21 .USB Cable .Video Cable
.Neck Strap .Eye Cap .Body Cap .Eyepiece Cap .SIGMA Photo Pro Disc
.SD1 Instruction Manual


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