Exmor CMOS sensor

The A700 is the first DSLR to feature Sony's new CMOS sensor (now christened 'Exmor' - apparently not named after the national park in Devon or its eponymous ponies). Actually to be more accurate it's the first DLSR that we know of to use the new sensor (other manufacturers tend not to boast about using Sony technology in their flagship cameras, but there has been some conjecture about the Nikon D300, for example).

But I digress. The interesting thing about the new Exmor sensor - announced a couple of months ago (see news story) - is that it takes a very different approach to A/D conversion (turning the analogue output of the sensor into the digital 0's and 1's that will be processed and turned into the final raw or JPEG file). Instead of using a separate A/D processor further down the imaging pipeline, the Exmor has lots of them built into CMOS sensor itself (there's one per column - that's over 4000 in this chip).

The advantage, in theory, is lower noise (though Sony's original technical documents talk about a big boost in speed too), since the analog pathway is greatly reduced and analog signal noise reduction can happen a lot earlier in the process. I'm not going to go into any more detail here about the technicalities of the Exmor sensor's unique design (mainly because the information we have is quite sketchy), but it is certainly an interesting development. We will be interested to see how well it performs in the real world (the proof, as with all these things, is in the pudding).

Below is how Sony makes this all seem very simple and friendly using evil spiky noise bugs getting mixed in with lovely golden balls of analog signal:

The A700's process in simple terms - the key thing here is that the job of turning each pixel's analog output into a digital file is split between the Exmor sensor (with on-chip column A/D conversion) and the Bionz processor (raw data NR and image processing).
In a conventional CCD-based system noise in the the analog output from the sensor builds due to the (relatively) long signal path before digital conversion.
The A700's sensor produces a digital output because there is an A/D converter on every column, meaning the analog signal path is short. This in theory means less noise in the analog signal and a cleaner output for the digital NR systems to work with.

Compared to Alpha 100 - key differences

Although the A700 and A100 are clearly aimed at very different parts of the market (entry level and advanced amateur) the mere fact that this is only Sony's second DSLR model means that many potential purchasers will be looking closely at what the key differences are. In the hand the design and construction gap between the two models is huge, but there are also some significant differences in the key spec - the cameras share very few components and only the metering system appears to be identical. The key differences be summed up simply as follows (there's a more detailed list in the table below):

• New 12MP CMOS sensor with on-chip A/D
• New 3.0" high resolution screen
• 'Semi pro' construction and environmental sealing (bigger and heavier too)
• Upgraded Autofocus system
• Faster continuous shooting (5fps)
• Additional Color Modes (now renamed Creative Styles)
• Pentaprism finder (vs Pentamirror) and interchangeable focus screens
• Vertical Grip option & remote control
• Hugely improved interface and ergonomics; more control, more customization options
• Scores of minor (and some major) feature enhancements

	Sony Alpha A700	Sony Alpha A100
Body material	• Aluminum chassis • Magnesium Alloy body shell • high grade plastic exterior • Environmental seals	• Plastic (interior construction unknown)
Sensor	• 23.5 x 15.6 mm CMOS sensor 'Exmor' • RGB Color Filter Array • Built-in fixed low-pass filter • 13.05 million total pixels • 12.25 million effective pixels • On-chip Column A/D Conversion & NR	• 23.6 x 15.8 mm CCD sensor • RGB Color Filter Array • Interline interlaced CCD • Built-in fixed low-pass filter • 10.8 million total pixels • 10.2 million effective pixels
Image sizes (3:2)	• 4288 x 2856 (L RAW ) • 4272 x 2848 (L) • 3104 x 2064 (M) • 2128 x 1424 (S)	• 3872 x 2592 (L) • 2896 x 1936 (M) • 1920 x 1280 (S)
Aspect ratios	• 3:2 • 16:9	3:2
File Formats	• Raw • Compressed Raw • Raw + JPEG • JPEG	• RAW • RAW + JPEG Fine • JPEG
JPEG compression	• Three level	• Two level
Auto Focus	• TTL CCD line sensors (11-points, 10 lines with center dual cross sensor) • EV 0 to 18 (ISO 100) detection range • Predictive focus control for moving subjects	• TTL CCD line sensors (9-points, 8 lines with center cross-hair sensor) • EV -1 to 18 (ISO 100) detection range • Predictive focus control for moving subjects
AF assist illuminator	• Yes (built-in LED lamp) • Range approx 1m - 7m	• Via internal flash, must be raised • 1.0 - 5.0 m range
Custom modes	Three	None
ISO sensitivities	• Auto (200 - 1600) - upper/lower limit selectable • ISO 100 • ISO 200 • ISO 400 • ISO 800 • ISO 1600 • Up to ISO 6400 (expanded range)	• Auto (100 - 800) • ISO 100 • ISO 200 • ISO 400 • ISO 800 • ISO 1600 • Lo80 (ISO 80, Low key) • Hi200 (ISO 200, High key)
Exposure compen.	• -3.0 to +3.0 EV • 0.3 or 0.5 EV steps	• -2.0 to +2.0 EV • 0.3 EV steps
Bracketing	• Single or continuous bracketing • 3 or 5 frames • 0.3, 0.5 or 0.7 EV steps	• 3 frames • 0.3 or 0.7 EV steps
Shutter speeds	• 30 to 1/8000 sec • Bulb	• 30 to 1/4000 sec • Bulb
Flash X-sync	• 1/250 sec • 1/200 sec (with Super SteadyShot on)	• 1/160 sec • 1/125 sec (with Super SteadyShot on)
Custom WB memories	Three	One
Color modes	• Standard • Vivid • Neutral • Clear • Deep • Light • Portrait • Landscape • Sunset • Night view • Autumn Leaves • B&W • Sepia • Adobe RGB	• Standard • Vivid • Portrait • Landscape • Sunset • Night view • B&W • Adobe RGB
Image parameters	• Contrast (-3 to +3) • Saturation (-3 to +3) • Sharpness (-3 to +3) • Zone Matching (-1 to +2 steps) • Brightness (-3 to +3 steps) (Available in all color modes)	• Contrast (-2 to +2) • Saturation (-2 to +2) • Sharpness (-2 to +2) (Available in all color modes)
Noise reduction	• Long exposure for exposures longer than 1 second • High ISO NR High/Normal/Low at ISO 1600 or higher • User controllable: On / Off	• Long exposure for exposures longer than 1 second • User controllable: On / Off
Continuous	• H: Approx 5fps max • L: Approx 3fps max • RAW: Up to 18 frames • cRAW (compressed): Up to 25 frames • RAW+JPEG: Up to 12 frames • JPEG (XFINE): Up to 16 frames • JPEG (STD/FINE): Unlimited (to card capacity)	• RAW: 3 fps, up to 6 frames • RAW+JPEG: 3 fps, up to 3 frames • JPEG: 3fps, unlimited
Viewfinder	• Optical glass pentaprism • Spherical Acute Matte focusing screen (interchangeable) • Magnification approx. 0.9x • Eye-relief 25 mm from eyepiece, 21 mm from frame	• Pentamirror • Spherical Acute Matte focusing screen (not changeable) • Magnification approx. x0.83 • Eye-relief 20 mm from eyepiece, 16 mm from frame
LCD monitor	• 3.0 " 'Xtra Fine' TFT LCD • 920,000 pixels • 270 ppi • Anti-reflective coating	• 2.5" TFT LCD ('Clear Photo LCD Plus') • 230,000 pixels • Anti-reflective coating
Control dials	Two	One
Video Out	• AV (Selectable NTSC or PAL) • HDMI (1920 x 1080i, 1280 x 720p, 720 x 580p, 720 x 576p) • 'PhotoTV' HD settings applied with BRAVIA TV	• AV (Selectable NTSC or PAL)
Storage	• Compact Flash Type I/II • Memory Stick Duo / Pro Duo	• Compact Flash Type I/II
Vertical Grip	Optional vertical Grip VG-C70AM	None
Dimensions	141.7 x 104.8 x 79.7 mm	133 x 95 x 71 mm (5.2 x 3.7 x 2.8 in)
Weight	• No battery: 690 g (1.5 lb) • With battery: 768 g (1.7 lb)	• No battery: 545 g (1.2 lb) • With battery: 638 g (1.4 lb)
Other	• New GUI and improved control • More customization options • AF/MF button • Improved DRO functionality • Wireless remote control • PC control via USB • Grip sensor • Improvements to Super SteadyShot • RGB histogram in playback mode • Clipped shadow warning in playback • New playback options • Flash Sync socket

Design compared to the A100

Although there is a vague family resemblance, the A700 is a very different camera to the A100 (the second dial has gone, for one thing). Yes, there are elements of (Konica) Minolta in there (particularly the Maxxum/Dynax 7 and 7D), but the Sony styling cues introduced with the A100 have developed significantly giving the A700 a real identity of its own. To my eyes it's not the most handsome camera ever built, but it's certainly a big step up from the first Sony DSLR (which looks and feels a little 'cheap' for want of a better word) - even if it lacks the finesse in detailing (such as surface textures and finishes) of something like the NIkon D200/D300. And in use it did start to grow on me.