Sigma SD10 Review

On October 27th 2003 Sigma announced the new SD10. This new X3 based digital SLR is the successor to the SD9 which was the first digital camera to utilize Foveon's unique X3 sensor technology (info here). The SD10 has a Sigma AF mount and, like the SD9, a Foveon X3 10M CMOS Sensor* which has 2268 x 1512 x 3 photodetectors (three photodetectors for each pixel location). With the advent of the SD10 both Sigma and Foveon are taking the (braver but) more logical position of using the number 10 million to represent the number of photodetectors, I'm sure this decision will be debated ad nauseam but it's easy to see their position, in our previous experience the X3 sensor delivers approximately twice the resolution of a standard mosaic sensor with the same number of horizontal and vertical pixel locations.

* The sensor in the SD10 is an improved version of the Pro 10M named the F7X3-C9110

History

• Foveon announce X3 sensor - 11th February 2002
• Sigma announce SD9 - 11th February 2002
• Our exclusive hands-on with an X3 sensor - 11th February 2002
• Foveon announces Adobe and Microsoft support - 23rd February 2002 *
• 2002 DIMA Innovative Digital Product Awards - 26th February 2002
• When is a pixel not a pixel? When it's three - 6th March 2002
• Our Sigma SD9 review - 26th November 2002

* It appears as though support is one thing, action something quite different

Sigma SD10 vs. SD9 the primary improvements

* Extended mode
** Photo Pro 2.0 improvements

• ISO sensitivity - The SD10's X3 sensor now utilizes Microlenses for improved sensitivity, the SD10 has two ISO modes. In the Default mode you can select from ISO 100 to 800 and take long exposures of up to 15 seconds at ISO 100, 4 seconds at other sensitivities. In Extended mode you can select from ISO 100 to 1600 and take long exposures of up to 30 seconds at any sensitivity.
   
• Battery system - Gone is the two battery system of the SD9, the SD10 now only requires the bottom battery tray which takes four AA type or two CR-V3 batteries. In addition the grip battery compartment is now buried making the grip thinner.
   
• Exposure compensation - Exposure can now be adjusted in third stop (1/3 EV) steps rather than half stop, this applies to aperture, shutter speed and exposure compensation. In addition the new EF500 Super/ST DG SA-N flash also supports third stop steps.
   
• Wireless TTL flash - This is now supported with the new EF500 Super/ST DG SA-N flash.
   
• X3F embedded rendering data - Photo Pro 2.0 now supports the storage of rendering data (adjustments to digital exposure compensation, contrast, saturation etc.) in each X3F file.
   
• X3 Fill Light - This excellent new feature of Photo Pro 2.0 allows you to add digital fill light to an image and raise the brightness of shadow areas only, decreasing this setting can be used to push shadows in darkness (useful for masking noise).
   
• Better image quality - Increased dynamic range, reduced noise, improved color accuracy. *
   
• Enhanced AF performance - New AF algorithm. *

* Claimed

X3 sensor background

Terminology

• Photodetector - A physical device used to capture a single color value (for a Bayer camera there is one of these per pixel location, the X3 sensor has three per pixel location)
• Pixel location - A location on the final image which contains full RGB color information

What's so good about this new X3 sensor?

In the example below we are simplifying things by using a 130 x 130 sensor, thus a total of 16,900 pixel locations in the output image. Obviously the same rules apply no matter many pixel locations the final image has.

Traditional "Mosaic" sensors

Digital cameras have for years used what is essentially a monochromatic (b&w) image sensor with individual color filters over each photodetector (known as the Bayer pattern and normally in a GRGB pattern). This means that each photodetector can only detect one of either red, green or blue light. Note that the green channel has twice the number of photodetectors as red or blue (this is because the majority of luminance information is carried in the green channel). A demosaic algorithm then combines the color of neighbouring pixels to reproduce the scene color at that pixel location.

Red 4,225 photodetectors	Green 8,450 photodetectors	Blue 4,225 photodetectors	Output 16,900 pixel locations

Foveon's X3 sensor

Foveon's sensor instead of having a single photodetector at each pixel location has a multi-layered design which has the equivalent of a red, green and blue photodetector at each pixel location. This means that instead of having to interpolate the values of neighbouring pixels the X3 sensor 'sees' full colour at individual pixel locations. This is pretty much the 'holy grail' of digital image sensors, it should mean ultra sharp, detailed images with full color single pixel resolution.

Note that this is a simplified drawing of how the chip works, for more detail see our news article at the time.

Red 16,900 photodetectors	Green 16,900 photodetectors	Blue 16,900 photodetectors	Output 16,900 pixel locations

Review Notes

Because of the similarity between the SD10 and the SD9 (they're almost identical externally) the first half of this review (body, operation, menus etc.) is based on my SD9 review which was posted in November 2002.