The core technology of the A37 is, of course, its SLT fixed mirror design. By using an electronic viewfinder, Sony removes the need to reflect light away from the image sensor and into an optical finder. This means that most of the light can be sent directly to the image sensor and there's no need for a complex moving mirror mechanism.
What makes the design distinct from 'mirrorless' camera designs is that the SLT still has a fixed, semi-transparent mirror constantly redirecting light onto the camera's DSLR-style phase-detection AF sensor. This not only means that it can quickly focus all Sony and Minolta A-mount lenses, but can continue to do so both while continuous shooting and shooting movies. Conventional DSLRs have to wait for the mirror to reset before they can take another focus measurement, meaning high speed continuous shooting tends to be reserved for professional level cameras.
The cost of having a mirror permanently in the optical path is a loss of light to the sensor. However, in the tests we've conducted so far, the 0.5EV increase in noise is negligible in real-world shooting.
Although Sony has never publicly stated that improvements were made to the A65 and A77 to prevent the occasional 'ghosting' (an offset double-image visible on where bright highlights were repeated over dark regions), it has hinted that the A37 could logically be expected to see any component improvements that those cameras had.
Like the A57, the A37 uses revised viewfinder optics to make the most of the same 1.44m dot equivalent display panel. It has has two viewfinder modes, a 'Maximum Magnification' mode and a 'Standard' mode that uses a smaller subset of the screen to give a longer eye-point (the distance from which the entire display can be seen), allowing easier use by wearers of glasses.
The LCD itself is a field-sequential device - it shows red, then green, then blue information rather than being able to show them all at the same time. The result is that you will sometimes see colorful tearing, often in your peripheral vision if you quickly look around the frame or blink. The degree to which you find this disconcerting is likely to be a personal issue, but it's another way in which the A37's viewfinder is inferior to the OLED unit in the high-end SLTs.
Auto Portrait Framing
Continuing the camera's beginner-friendly theme, the A37 gains the 'Auto Portrait Framing' mode we first saw on the A57. This will try to re-crop images containing faces, if it thinks there's a better portrait image to be had from it. Based on a combination of face detection and the rule-of-thirds, Auto Portrait Framing will identify where the subject's eyes are and crop the image, to put the eyes one third of the way down the frame.
This crop frame is shown on the rear display, just after you've taken your picture, so that you can see how the camera thinks you should have composed the shot. It then takes the cropped region of the photo and resizes it back up to full resolution and saves this resized image alongside your original one. The system will attempt to leave more of the background image on the side that the subject is facing, so that you don't end up with pictures of people staring into the edge of the frame.
|Original image||Camera re-cropped and upscaled portrait image|
Clear Image Zoom
The A37 uses the 'By Pixel Super Resolution' we first saw in the A57. In both Auto Portrait Framing mode or in its Clear Image Zoom mode (which offers up to 2x magnification), it uses this technology. The theory is that it intelligently interpolates between pixels as it up-sizes. By comparing each image element to a database of patterns it can attempt to add more detail than simple upscaling would allow.
We'll look at the feature more closely in our full review, but Sony's statement that the quality of this digital zooming is 'nearly equivalent' to optical zooming with the kit zoom is either a rather grand claim or a bit of a dig at the quality of the kit zoom.
Because the AF sensor needs a fairly wide aperture to make sure it's fully illuminated, the camera will only autofocus in P mode, but if you're happy to do without AF, you can take more control of the exposure settings in A, S or M modes. You have the choice of setting ISO manually (between 100 and 3200), or engaging Auto ISO across the same range. As with stills mode, there's no option to control the range over which Auto ISO operates.
The A37 gains the 'focus peaking' manual focus aid that is particularly useful for video shooting. This highlights high-contrast edges, making it easy to see when you're approaching (and passing) optimal focus. This one feature makes it considerably more practical to manually focus on those occasions when you want to take precise control over the camera's movie exposure. This, along with the option to add an external mic, make the A37 an interesting camera for enthusiast movie shooters.