It’s no secret that the original Sony a7r full frame mirrorless camera is one of my two or three favorite cameras, which I have been using on a daily basis since late 2013. Coupled with the Zeiss “holy trinity” of lenses (16-35mm, 24-70mm, and 70-200mm optics, each with an f/4 maximum aperture), I’ve prized the high-end model for its combination of image quality, high resolution 36MP sensor, compact size, and full feature set. And, since the introduction of the first of the new generation mirrorless full frame models — the 24MP Sony a7 II — I’ve been looking forward to the successor to my original a7r, which was introduced on June 10, with availability slated for August, 2015. Does this new model justify the level of anticipation that we’ve seen? I’ve put together a list of the most important new features.

• Surprise! The new camera’s 42.4 megapixel resolution is not the most significant feature. What Sony owners will absolutely love is the potential autofocus speed increase possible with the a7r II. To understand why, you need to consider that the largest image capture bottleneck in most mirrorless cameras (and in dSLRs in “mirrorless” Live View mode), is the crippling slowness of conventional contrast detect AF.

When focusing using the image captured by the sensor alone, a camera must tediously examine the edge contrast of parts of the subject and, frequently, hunt back and forth until the highest contrast (sharpest) image is found. Many mirrorless cameras use nothing but contrast detection, and even optimized systems may not be as speedy in achieving focus as the slowest dSLR that relies on contrast detection. The chief advantage of contrast detect AF is that focus isn’t restricted to a small set of AF sensors, as well as the systems’ relative simplicity.

The a7r II’s back-illuminated Exmor R CMOS sensor has 399 phase detection AF points embedded within its full frame. That means the camera can use rangefinder-like phase detection to achieve focus much more quickly, up to 40 percent faster than the previous model, according to Sony. “Hunting” isn’t necessary; by examining the AF points, the camera knows instantly which direction to focus, and exactly how much of an adjustment to make. This superior phase detect AF can bring the a7r II up to the level of premium dSLR cameras in terms of autofocus. An additional 25 contrast detection points are also used as required in Sony’s Fast Hybrid system.

• Five-axis image stabilization. Sony introduced 5-axis SteadyShot IS with the 24MP a7 II. It’s an in-body system that works with virtually every lens, and makes adjustments along the x and y axes, and compensates for pitch, roll, and yaw, too. (In plain English, x and y movement of the camera is along the focal plane in the left/right, up/down directions, respectively; pitch is tilting the camera up or down; roll is rotating the camera along a line passing through the center of the lens; yaw is rotating the camera from side to side along the axis of, say, the tripod socket.) Depending on camera movement, any one of these or any combination may occur as you frame and shoot.
  This enhanced SteadyShot should give you a conservative minimum of two or three stops (i.e. you can shoot at 1/30th s where 1/250th s might be required before), and potentially much more. (Keep in mind that IS does nothing to prevent subject blur.) Since the a7-series cameras are so compact and light in weight, the ability to use them without a tripod in many situations is a significant advance.
  As a bonus, if you own a lot of old Minolta or newer Sony A-mount lenses, you can use them with the a7r II and the EA-LA4 adapter. You lose a bit of compactness, but gain versatility without sacrificing AF speed.

• Back-illuminated CMOS sensor. Sony pioneered back-illuminated sensor technology, and cleverly applies it to the new a7r II. With conventional sensors, the matrix of photosites and the “wiring” they require reflect some of the light striking them, preventing that illumination from reaching the photosensitive layer that actually captures the image. For a back-illuminated sensor, the order of the layers is reversed, so the illumination falls directly on the photosensitive elements, with the matrix and wiring relegated to the reverse side. That allows the sensor to use virtually 100 percent of its area to capture light, making it more sensitive. There is no optical low pass “blurring” filter in front of the sensor, enhancing resolution (you may need to remove moire manually.)
  This configuration provides three benefits. Sony has been able to squeeze 42.4 megapixels onto a 24 x 36mm sensor without needing to reduce their size as much as would be required with a conventional sensor. That translates into improved sensitivity, too. The a7r II should provide improved image quality at ISO settings up to 25,600. When production models are available, we’ll see whether the improvements will make photography at the equivalent of ISO 102,400 possible as well.
  The back-illumination configuration also allows improving the wiring on the back of the sensor (because there is no longer any concern about its interfering with light gathering), such that Sony says data transmission can occur up to 3.5x faster than with the original a7r.
  An anti-reflective coating on the surface of the sensor helps improve light gathering — and also should reduce problems you might face from light bouncing off the sensor, and then bouncing back from the rear elements of your lenses (frequently older, pre-digital lenses.)
  Don’t expect the a7 II to rival the current a7s for the low-light championship, but the results should be good. Best of all, you won’t need to make some difficult choices about bumping up the ISO while reducing image quality. You should be able to have some cake, and eat it, too.

• Other goodies: Videographers will like the ability to shoot and record 4K video in multiple formats including Super 35mm (without pixel binning) and full-frame format, a world’s first for digital cameras . The rest of us should love a shutter with 50% less vibration, and which includes a (virtually) Silent Shooting mode. The optional electronic first curtain shutter can further reduce shutter shake. The XGA 2,359,296-pixel organic light emiting diode (OLED) viewfinder now boasts a 0.78 magnification, and the 1.2MP rear-panel LCD remains. Wi-Fi and NFC (near field communications) allows the a7r II to communicate with your favorite Android and iOS devices.