Sigma SD15 Brochure & Specs

The Inside Story
The founding of FOVEON
Foveon's invention of the X3® direct
image sensor traces its roots back
to the research of Caltech physicist,
Professor Carver Mead. One focus of
Mead's research was the modeling
in semiconductors of human
capabilities. Mead's collaboration
with a neuroscience research group
eventually led him and his students
into fundamental investigations of the
image sensing process.
Mead's research led to a business
venture supported by some of Silicon
Valley's leading firms with both
financial and human resources. In
August 1997, Foveon was founded,
taking its name from an anatomical
term: fovea centralis.
Maximal sensitivity to light and color
The fovea centralis is the central
portion of the human retina that has
the most acute vision and the best
color perception. The name “Foveon”
signaled the company's commitment
to developing the world's most
advanced and high-performance
image sensors for the professional
market. From its first days as a
startup company, Foveon gathered
the best imaging engineering talent
available and engaged in cutting-
edge research and development.
Foveon's first product was not an
image sensor but instead a complete
digital camera. In this original system,
a beam-splitter prism assembly
separated the incoming light into
its three primary colors, passing the
red, green, and blue beams through
separate color filters and directing
them to three large image sensors.
An extremely high-resolution image
was then assembled from the data of
the three colors.
This camera was extraordinary, high-
end technology, but it was expensive
to manufacture and ultimately too
costly for the end user. By the time
Foveon stopped prism digital camera
production, it had already created
a patented technology that would
ensure its preeminence in the coming
era of image processing research.
The invention of
a revolutionary device
Next, Dick Merrill, a leading
semiconductor engineering working
at Foveon, invented a device that
could create a stack of RGB pixels
in each pixel location. Thanks to
his special genius and a unique
career, Merrill had developed
the creativity needed to realize
artistic objectives through
advanced technology. His ability
as a photographer led to crucial
technological contributions, and
his passion for artistic expression
became the driving force behind
the invention and development
of Foveon's advanced, full-color
image sensors.
A new era in image processing
Merrill's device proved the
feasibility of capturing RGB
information in each pixel location,
but it was not immediately possible
to develop an image sensor based
on this technology. Although it was
well known that silicon absorbs
shorter wavelengths of light
closer to its surface and longer
wavelengths of light further from
its surface, additional advances in
image processing were necessary
to make use of this characteristic in
creating high-quality images. That
task fell to Foveon Chief Scientist
Dick Lyon, an image processing
expert with a keen interest in
photography.
Professor Carver Mead The First Three-layer Direct Image Sensor Professor Mead and Dick Lyon working with the prism camera
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Sigma SD15 Specifications

General

Camera Type	Interchangeable Lens SLR Type Digital Camera
Image Sensor Size	13.8 x 20.7mm
Lenses Used	Sigma SA Mount Lenses
Picture Angle	Equivalent to 1.7x the focal length of a lens when used on a 35mm SLR camera.
Lens Mount	SA mount
Imaging Element Type	FOVEON® X3™ (CMOS)
Color Photo Detectors	14.06 Million (2652 Columns x 1768 Rows x 3 Layers)
Image Recording Format	Lossless compression RAW Data (12bit), JEPG
White Balance	8 Type (Auto, Sunlight, Shade, Overcast, Incandescent, Fluorescent, Flash, Custom white balance)
Viewfinder Type	Pentaprism SLR Viewfinder
Viewfinder Frame Coverage	98％ horizontal, 98％ vertical
Viewfinder Magnification	0.9x (50mm F1.4 at infinity)
Eyepoint	18mm
Diopter Adjustment Range	-3dpt to +1.5dpt
Auto Focus Type	TTL phase difference detection system
AF Operating Range	EV 0 to 18 (ISO100)
Focus Mode	Single AF, Continuous AF (AF Predict function), MF
Metering Systems	Evaluative Metering, Center-Weighted Average Metering, Center Area Metering, Spot metering
Metering Range	EV 1 to 20 (with 50mm F1.4 at ISO100)
Exposure Modes	(P) Program AE、(A) Aperture Priority AE、 (S) Shutter Speed Priority AE、(M) Manual
ISO Sensivity	ISO (50), 100, 200, 400, 800, 1600, (3200) *( )Extended Mode
Exposure Compensation	±3EV (in 1/3steps)
AE Lock	Push button type
Auto Bracketing	Three or five frames (in 1/3steps, Appropriate Exposure – Under Exposure – Over Exposure)
Shutter Type	Vertical-travel metal focal plane shutter, electronically controlled through entire speed range
Storage Media	SD Card / Compatible with SDHC, Multi Media Card
Aspect Ratio	3：2
Resolution	HI：2640 x 1760 MED：1872 x 1248, LOW：1312 x 880
Interfaces	USB 2.0, Video Out (NTSC／PAL)