Introduction Sony's a7C is an attempt at a compact full-frame camera that retains the capability of a larger model. It has an awful lot in common with the still-available a7 III, with sensor, processor and most key specifications shared between the two models.
However, while the $1800 launch price of the a7C is $200 lower than that of the a7 III, the bigger camera has been on the market for more than two years longer and consequently sells for much less in many places.
So which camera is better for your needs?
What's the same?
An awful lot of the specs and capabilities of the two cameras are a match: 5-axis stabilized 24MP BSI CMOS sensors, Bionz X processors, 10 fps shooting and 8-bit 4K video capture from the full width of those sensors.
The cameras have the same basic menu layout and the same touchscreen implementation, only really using the screen to position the AF point. Both offer Wi-Fi, with the a7C gaining the ability to use the 5Ghz band, both also have NFC for making a fast connection but, though they each include Bluetooth, both use it solely for transferring GPS data, rather than maintaining a constant smartphone connection.
So, in terms of broad capability, there's not much to choose between them, but once you dig into the details, there may be differences that mean it comes down to more than simply price versus compactness for you.
What's different - Autofocus
One of the biggest differences is the behavior of the cameras' autofocus systems. The a7C has the latest version of Sony's AI-trained subject recognition system, which is fully integrated into the main AF system. If you choose the tracking variant of one of its AF area modes, the camera will confidently stay glued to that subject, regardless of how the subject and camera move, relative to one another.
If the subject is human it will engage body, head, face or eye-detection as appropriate. It can perform a similar trick for certain types of animal, if you tell it to prioritize such subjects.
The a7 III is pretty good but not quite as polished, by comparison. Eye-AF works very well but the AF system won't necessarily continue to track that same subject if they look away. Its subject tracking is also less dependable, and tries to follow the whole subject, not necessarily the part of the subject you've specified, making it less precise and less predictable than the a7C's system.
What's different - Viewfinder
Another really significant difference is the viewfinders. Although both have relatively low resolution (for modern cameras costing this much), the a7 III has a larger viewfinder panel with optics that combine to provide decent 0. 78x magnification. That's as big as the finders on pro sports DSLRs.
The viewfinder on the a7C uses a smaller panel and achieves a rather paltry 0. 59x magnification, which is more directly comparable with a mid-range APS-C DSLR. In addition to its small size, the a7C's finder has little in the way of an eye-cup: it's got a thin rubber surround for comfort (and the avoidance of scratches for glasses wearers), but nothing to stop light from around the finder reaching your eye. This is probably the biggest concession made to keeping the camera small.
What's different - Size
The most significant difference, though, is the a7C's size, compared with the a7 III. It's a significantly smaller camera, especially when paired with the retractable 28-60mm F4-5. 6 kit zoom.
This isn't enough to make the a7C pocketable by any means, but means it can operate as a package that's much easier to have with you at all times. This benefit is greatly reduced if you fit one of the system's larger lenses, such as the do-everything 24-105mm F4, but there are options, such as the 35mm F1. 8 and 85mm F1. 8 that keep the combination small and allow the camera to show its full strength.
What's different - ergonomics
The a7C's reduction in size also means a change in ergonomics. Impressively, the smaller camera still finds room for two command dials and a dedicated exposure comp dials, as well as a prominent AF-On button on the back. The downside is that all three dials are positioned to be controlled by your thumb. So, while it's possible to access, say, aperture, shutter speed and exposure compensation without the need for button pressing, it requires a degree of hand-re-positioning, which slows the process down.
By comparison, the a7 III has front and rear command dials, that allow thumb-and-forefinger control without repositioning your hand. It too has an exposure compensation dial and a command dial on the rear face of the camera, if you need to control more than two parameters on-the-fly. The a7 III also has an AF joystick, though doesn't benefit from the larger AF-On button we've seen on more recent Sonys. The a7C's AF system doesn't demand the use of an AF joystick very often, but it's something a lot of photographers feel is nice to have.
What's different - Shutter
A less visible difference between the two cameras is their use of different shutter mechanisms. The a7 III has a conventional mechanical shutter with the option to use an electronic first curtain to reduce the risk of shutter shock, and a silent, fully electronic mode.
The a7C only has a mechanical return shutter, meaning it can only offer electronic first curtain or fully electronic modes. The use of EFCS reduces the risk of shake at moderate shutter speeds but can also have a damaging impact on out-of-focus rendering if used at very high shutter speeds and a wide-aperture (we only saw the slightest impact at 1/4000 sec and F1. 8, for instance). The bigger restriction might be that the new shutter is limited to 1/160 sec flash sync speed and 1/4000 sec maximum shutter speed, though e-shutter extends to 1/8000 sec if your subject and lighting will allow.
What's different - Video
For the most part, the a7C and a7 III have very, very similar video specifications. Both cameras shoot oversampled 4K/24p from the full width of their sensors, or have to crop-in slightly for 30p. Both offer the ability to shoot S-Log2 and S-Log3 or some versions of the HLG curve designed for use on HDR TVs, but all video modes are captured in 8-bit, which limits the flexibility of the footage.
What's different is the AF performance in video mode. Frustratingly you need to change the touchscreen settings and tap a subject to access subject tracking but it works extremely well, and uses the full face/eye/body recognition capabilities. The a7 III uses a less sophisticated AF system that requires more button pressing to engage tracking and tends not to be as dependable, once you have.
Conclusion
At its most simple, there's so much that's similar about the a7 III and a7C, that the main factors to choose between them are compactness and price. If you don't need or appreciate the smaller form-factor of the a7C or you expect to use larger lenses, you may well decide that the less-expensive a7 III is a better choice.
Equally, the larger viewfinder and more DSLR-like dial setup may make the a7 III's ergonomics preferable to some photographers.
However, the a7C's autofocus is meaningfully better than that of the older camera, both in performance and ease-of-use which, combined with its smaller body, compact kit lens and impressive battery life, make it a really powerful option for travel. It all comes down to what you plan to do with your camera.
. dpreview.com2020-11-4 16:00
