Compared to Alpha 900

On the next two pages we'll cover the areas where the Sony DSLR-A850 and its bigger brother, the DSLR A900 are identical, and what the differences in specification, design, performance and image quality are. Reading this article plus our in-depth Sony DSLR-A900 review will give you all the information about the Sony A850 that you'd expect from a dpreview DSLR review.

Visually the Sony A850 and A900 are virtually identical. On the outside there is, apart from the type label and a slightly matter black finish on the A850, no difference between the two camera bodies. The two Sonys might not be an outstanding example of innovative design nor are they very pretty (all a matter of opinion of course) but they are without a doubt very well built. The operational controls are laid out in a clean, logical and functional way that marries a sensible level of external control (there's a large number of buttons on the body) with an excellent on-screen control system.

Key differences

As we mentioned above differences between the A850 and its bigger brother, the A900, can only be found underneath the hood. A look through the viewfinder will reveal one of them. While the viewfinders' construction is very similar the A850's variant 'only' offers 98% frame coverage making it slightly smaller. The other noticeable difference is a smaller buffer size on the A850 which results in a slower continuous shooting speed - three frames per second vs the A900's five. The table below provides an overview of the cameras' key specifications with the differences highlighted.


Sony Alpha A850

Sony Alpha A900
Body material • Magnesium Alloy Chassis and exterior
• Environmental seals
Sensor • 35.9 x 24.0 mm CMOS sensor 'Exmor'
• RGB Color Filter Array
• Built-in fixed low-pass filter
• 25.7 million total pixels
• 24.6 million effective pixels
• On-chip Column A/D Conversion & NR
Processor Dual Bionz
Crop Factor 1x
Image sizes (3:2) • 6048 x 4032 (24M 3:2)
• 4400 x 2936 (13M 3:2)
• 3024 x 2016 (6.1M 3:2)
• 3924 x 2656 (11M APSC)
• 2896 x 1928 (5.6M APSC)
• 1984 x 1320 (2.6M APSC)
Auto Focus • TTL CCD line sensors (9-points, center dual cross types + 10 assist sensors)
Custom modes Three
Bracketing • Single or continuous bracketing
• 3 or 5 frames
• 0.3, 0.5 , 0.7 or 2.0 EV steps
(2.0 EV steps for 3 exposures only)
Continuous • Approx 3 fps max
• RAW: Up to 16 frames
• cRAW (compressed): Up to 18 frames
• RAW+JPEG: Up to12 frames
• cRAW+JPEG : Up to 12 frames
• JPEG (XFINE): Up to 34 frames
• JPEG (STD/FINE): 593/384
• H: Approx 5fps max
• L: Approx 3fps max
• RAW: Up to 12 frames
• cRAW (compressed): Up to 25 frames
• RAW+JPEG: Up to 10 frames
• JPEG (XFINE): Up to 11 frames
• JPEG (STD/FINE): 285/105

• Optical glass pentaprism
• Spherical Acute Matte focusing screen (interchangeable)
• Frame coverage approx 98%
• Magnification approx. 0.74x
• Eye-relief 20 mm from eyepiece, 21 mm from frame
• Eyepiece shutter

• Optical glass pentaprism
• Spherical Acute Matte focusing screen (interchangeable)
• Frame coverage approx 100%
• Magnification approx. 0.74x
• Eye-relief 20 mm from eyepiece, 21 mm from frame
• Eyepiece shutter
Vertical Grip Optional vertical Grip VG-C90AM
Dimensions 156 x 117 x 82 mm
Weight • No battery: 850 g
• With battery: 895 g
Other • Intelligent Preview mode
• New raw converter software
• AF Micro Adjustment
• Top LCD panel


As we've described above the A850's viewfinder is one of the key differences to the A900. Externally there's no difference, but the A850 viewfinder offers 98% coverage vs the A900's 100% and is therefore fractionally smaller. Having said that, with its large and bright image the A900 viewfinder is is one of the nicest DSLR viewfinders we've ever had the pleasure to look through and the A850 is not far off. You won't miss live view when focusing manually and to anyone previously using an APS-C DSLR the viewfinder is still a revelation.

Viewfinder size

One figure hidden away in every SLR's spec is the size of the viewfinder (often in a format that makes comparison between competing models impossible). The size of the viewfinder is a key factor in the usability of an SLR - the bigger it is, the easier it is to frame and focus your shots, and the more enjoyable and involving process it is.

Because of the way viewfinders are measured (using a fixed lens, rather than a lens of equivalent magnification), you also need to take the sensor size into account, so the numbers in the diagram below are the manufacturer's specified magnifications divided by the respective 'crop factors'. As you can see, the A850 viewfinder (red line) is only fractionally smaller than the Canon EOS 1Ds Mark III which has the currently largest viewfinder of all DSLRs on the market. However, the A850's viewfinder is significantly larger than its counterpart on any APS-C DSLR. For this diagram we have included the Canon EOS 550D.

As you can see the A850's viewfinder is only marginally smaller than the Canon EOS 1Ds Mark III's equivalent but signficantly larger than the EOS 550D's.

Viewfinder crop

As you can see below on the A850 a tiny proportion of the frame is not visible in the viewfinder. As a result, you don't get exactly to see what the sensor will record, but even at 98% frame coverage framing and composing an image is still a pleasure with the A850.

Sony DSLR-A850: 98% viewfinder.