Pro Review: Sony (alpha) DSLR-A900
By Ron Eggers
When the Sony (alpha) DSLR-A900 camera hit the market, it had the highest resolution available in a digital SLR. With a 24.6-megapixel Exmor CMOS sensor and maximum image resolution of 6,048x4,032 pixels, it has more than double the resolution of the previous model, the A700, and is the first Sony digital body with a full-frame (35mm-size) sensor. Aside from the A900’s much higher, the two models have similar shooting characteristics, ergonomics and menu structures.
My first experience with the A900 was with a prototype version during a Sony-sponsored shooting excursion in late summer 2008. I wasn't convinced that Sony’s target market, the serious photo enthusiast, really needed such high resolution, particularly if it came at the expense of image quality, color fidelity, shooting speed, and responsiveness. But after that first experience, followed by a couple of weeks working with a production model, any trade-off was obviously minimal. It’s not so much that the camera’s resolution is too high for its target market, it’s more like Sony undershot the target market.
Among the reasons Minolta equipment users cite for switching to Sony is that they can use the lenses and accessories they already have with the new bodies. That’s true, but with the quality of Sony’s latest equipment, it’s time to consider choosing Sony gear on its own merits. To get the most out of the new Sony bodies and the highest quality images, it’s best to pair them with the lenses and lighting units being developed specifically for these models.
Often, boosting a model’s resolution slows down its shooting speed, but not with the A900. It’s fast enough for just about any professional application, with a rated capture rate of 5 JPEG frames per second (fps). In my trials, using a SanDisk 4GB Extreme IV UDMA CompactFlash card, which supports transfer rates up to 45MB per second, the actual performance matched the specs. I could take 49 frames in 10 seconds. With two memory card slots, the camera accepts both CF cards and memory sticks.
In JPEG mode, the burst rate is impressive. At maximum resolution, I could take 576 frames of the same scene in 120 seconds. I probably could have continued shooting indefinitely if I’d had a larger capacity card. The raw burst rate was lower, 14 frames in about 3.3 seconds, and then the camera started shoot at an irregular pace. Within 10 seconds, I took 23 raw frames.
Focusing is fast. The A900’s autofocus system includes nine focusing points and 10 assist points. It’s 40-segment multi-pattern metering system is effective under a variety of lighting conditions.
Now, capturing a high-resolution image doesn't necessarily mean you'll wind up with a high-quality shot, and image quality is the acid test for any camera model. Coming up with clean images with so many pixels packed into a sensor, even a full-frame sensor, is difficult, as it increases electronic noise. Other factors can have an impact on noise levels as well, yet noise level can be controlled. Most DSLRs have a single image-processing pipeline, but the A900 is equipped with dual BIONZ image processing engines to provide the capture speed and the image quality required for such high-resolution images.
Analog images are captured by the sensor, which applies the first level of noise reduction (NR), before the analog-to-digital (A/D) conversion takes place. A/D conversion is handled at the chip level. A certain amount of digital noise reduction is applied to all images by the sensor, even with the NR turned off. A higher amount of NR is automatically applied to any exposure longer than 1 second. With the NR function switched on, it can be applied to shorter exposures.
It’s also possible to apply NR to high ISO images; the camera’s NR can be set to high, standard, low or off, depending on how much is required. The advantage of having shooting with NR turned on is seeing less noise in the captured images. The disadvantage is that it slows down image capture, sometimes significantly. You cannot take another shot until the noise reduction has been applied and the image is processed, so even with dual image-processing engines, it’s best to use NR only when needed.
This low-light image was taken at 1/500 second at f/11, ISO 200, with no noise reduction and EV +0.7. Click the top image for a 2000-pixel width view saved for Web at 60 quality setting. The lower image is a 100% crop saved for the Web at quality setting 100. ©Ron Eggers
The dynamic range of the A900 can be optimized with its D-Range Optimizer, which provides optical brightness and contrast control. D-range optimization is particularly effective in high-contrast situations, such as backlit scenes. Set to standard mode, the optimizer analyzes the image as a whole, then adjusts for optimum brightness and contrast. In the advanced auto mode, the camera analyzes the image in segments, then adjusts the optimum D-range for each segment. There are five settings for D-range levels, giving you control over how much the image is actually changed.
The difference between using D-range optimization and not using it is quite noticeable. Even though the f-stop and shutter speed is the same in both of the model shots, with D-range optimization turned off, the image exhibits quite high contrast. Set to maximum, the exposure is much more natural. D-range bracketing definitely extends creative control.
This extreme example shows the difference between of a high contrast image with the D-range optimization turned off (left) and set to maxium (right). Both images were exposed for 1/250 second at f/5.6, ISO 200. ©Ron Eggers, model: Shawnna Martinez
The A900 has an integrated image stabilization system. Sony's SteadyShot Inside anti-shake system enable the camera to pick up two to three stops beyond the usual with handheld shooting. The advantage of in-camera stabilization over one simply lens-based stabilization, is that it works with any compatible lens, not solely the more expensive IS lenses.
There are four basic groups of menus, each with multiple screens’ worth of options. There are way too many options to cover here, but I will mention that it would be easier to navigate through them all if the menus were color-coded. Fortunately, there are quicker ways to make adjustments than through the menus. The quickest way to adjust just one setting, which you can assign, is to use the custom button on the back of the camera body.
For multiple adjustments, it’s quickest to hit the function button, which brings up the data on the LCD screen. The most recent adjustment will be highlighted, then you can use the multi-selector to navigate through the various options. Pressing down on the selector brings up that setting’s options. It's much quicker and easier than navigating through myriad menus.
The Sony A900 DSLR is a solid piece of equipment. Built in a magnesium alloy shell, without the optional vertical grip, it weights just slightly over 2 pounds. With the Carl Zeiss Vario-Sonnar 2.8/24-70 ZA lens that that was provided for this review, it weighs 4.4 pounds. That's a great shooting combination. Unfortunately, extra weight is frequently an unavoidable trade-off for shooting with a fast, high-quality lens such as the new Zeiss.
With the A900’s full-frame sensor, there's no lens conversion factor. Conventional 35mm lenses shoot at their designated focal lengths. The A900 can also be set to capture APS-C-size images, so you can also use lenses designed for that format.
As you’d expect with a high-resolution sensor, the capture files are large indeed. Depending on the subject matter and amount of compression, JPEG files can weigh in at 18MB or more, RAW files at 26MB.
With the high-resolution A900 DSLR, Sony’s equipment can now compete with any system. Price: $2,999.99.
SONY (alpha) DSLR-A900 SPECS
Sensor: 24.6-megapixel full-frame Exmor CMOS sensor
Image processing: dual BIONZ image processing engines
Resolution: 6,048x4,032 pixels
Metering: 40-segment multi-pattern system
Autofocus: nine-point AF system with 10-point assist
ISO Range: 100-6400
Shutter Speed: 30 seconds to 1/8,000 second
Image Stabilization: in-camera SteadyShot camera stabilization
LCD: 3.0 inches, 921,000 pixels
Lens mount: Alpha mount
Price: $2,999.95 (body only)