Seeing how the a7 is a high-end full-frame camera, you'd expect top-notch performance and, for the most part, that's what you'll get. While the a7's autofocus system is responsive, the camera takes a while to start up. Continuous shooting is respectable, and battery life is typical of mirrorless cameras (which means that you might want to bring a spare).
While most mirrorless cameras start up in under a second, the a7 isn't ready to shoot for nearly two. We've also noticed that if the power is quickly cycled, this delay can be double that. Interestingly enough, the camera is ready to shoot in nearly half a second with no lens attached, so the delay may have something to do with initializing the lens.
As one would expect, there's no noticeable shutter lag on the a7. In terms of shot-to-shot speeds, you'll wait around 0.6 seconds between Raw+JPEG shots, and slightly less if you're sticking to JPEG.
AF System & Performance
The a7 uses a hybrid AF system, which puts 117 phase-detect points onto the camera's CMOS sensor, alongside 25 contrast-detect AF points. This hybrid AF system allows the camera to ascertain not only the direction to move the lens to achieve focus, but also how far. This has a number of advantages over the contrast detection focus method traditionally used by compact and mirrorless cameras, which requires the lens to scan through its focus positions while the camera checks whether it is becoming more in or out of focus.
The ability to collect this depth information not only means that focus can be performed faster (because the camera can push the lens straight to the right place, rather than having to scan through its whole range), but also brings advantages for continuous focus and for focusing during movies. In movies, for instance, because the camera has a good understanding of depth, it should reduce the risk of the camera suddenly losing a moving subject and scanning off to infinity and back looking for it (and ruining your movie by doing so).
|Sony's Hybrid AF system on the a7 uses an array of 117 phase-detection points spread out across the center of the sensor, which are represented by the red crosses. The 25 contrast-detect points are in green.|
Overall, we found the AF system to be responsive and accurate in most situations. In good light the camera focused quickly, with very little 'hunting' by the AF system. Low light focusing was a bit different. The a7 sometimes hunted, which resulted in slower (but not horrible) focus times. Strangely, the camera focuses faster and more accurately in wide AF mode with the AF-assist lamp turned off.
The a7 offers two different continuous shooting modes: standard (2.5 fps) and speed priority (5 fps). As its name suggests, speed priority mode shoots faster than regular continuous, but for a much shorter duration.
Thanks to the its hybrid AF system, the a7 will attempt to keep your subject in focus, even when shooting in speed priority mode. However, should your subject wander out of the Phase Detect area, you'll lose that benefit, and the camera reverts to contrast-detection.
Here's what kind of performance you can expect from the two burst modes on the a7. We used a SanDisk Extreme Pro (95Mb/sec) SDHC card to measure the speed.
Large/Xtra Fine JPEG
|Frame rate||2.5 fps||2.6 fps||2.6 fps|
|Number of frames||To card capacity||43 shots||33 shots|
|Buffer full rate||N/A||1.5 fps||1.2 fps|
|Write complete||See below||10 secs||19 secs|
The a7 hits its advertised speeds in its standard continuous mode, and its large buffer size allows you to shoot at full speed for quite a while. Clearing the buffer can take some time, during which time you cannot enter the menus or playback mode. For JPEG shooting, this delay depends on the number of photos you've taken. For example, the a7 is locked up for 11 seconds when ~25 JPEGs are taken.
The view on the LCD/EVF is in real-time when shooting in standard continuous mode.
Speed Priority mode
The speed priority continuous mode lets you shoot at rates of 5 fps according to Sony. By default, the camera locks focus on the first shot, but on the a7 you can turn on continuous AF, if you wish. Here's how the Alpha 7 performed at its faster speeds:
Large/Xtra Fine JPEG
|Frame rate||4.8 fps||4.8 fps||4.7 fps|
|Number of frames||To card capacity||28 shots||25 shots|
|Buffer full rate||N/A||1.4 fps||1.1 fps|
|Write complete||See below||11 secs||19 secs|
While the a7 met or exceeded its advertised rates in regular continuous mode, the opposite is true in speed priority mode. Still, the performance is respectable, and there's just a slight dip in the burst rate when using continuous AF. For example, the JPEG drops from 4.8 to 4.6 fps, which most people won't notice. The lock-up delay when shooting JPEGs is the same as it is for regular continuous mode.
The a7 does not provide live view in Speed Priority mode.
The a7 uses the same NP-FW50 InfoLithium battery found on many other Sony cameras. The NP-FW50 has 7.7Wh of energy, which Sony claims will provide 340 shots per charge. That's very low, considering that the a7 has no built-in flash, which is normally included in the CIPA battery life numbers. Do note that using Wi-Fi frequently will put extra strain on the battery.
Despite the cost of the a7, Sony does not provide an external charger. Rather, you use an AC-to-USB cable (or just your PC) to fill up the FW50 battery. Charging via the USB adapter takes a whopping 310 minutes, so it makes a lot of sense to pick up one of the BC-TRW or BC-VW1 external chargers, which are both considerably faster (especially the latter).