Sony's Alpha 7S, with its outstanding low light performance and full-frame, full-sensor video readout, is now right at the top of the list for those looking for an alternative to the "convientional" video DSLRs.
The 7S is currently available in the US and imminent in the UK (for reasons, presumably, of firmware, of which more anon). The basic stats are straightforward: it's a full-frame, electronic viewfinder stills camera with a 12.2 megapixel sensor, and a touch cheaper than a Canon 5D Mk. III. Externally the camera is similar in appearance to the A7R, although my intention here is to discuss it as a filmmaker's camera as opposed to discussing the advances between models.
Perhaps unfairly, I notice that the A7S is widely compared to Panasonic's GH4, the other effective option for people who need 4K in a DSLR-sized package (though both are full-time live view cameras with an electronic viewfinder and therefore not, strictly speaking, DSLRs). The 7S is positioned more to compete with the higher end of Canon's full-frame range as a stills camera, but from a moving-image perspective Panasonic may be the obvious competitor, cheaper as it is.
Both cameras offer uncompressed HDMI output – or at least the A7S reportedly will. The review sample was supplied with unfinished firmware which did not, at time of writing, know how to do 4K HDMI output, so I couldn't test the feature. Because of the unfinished firmware, I have made only subjective analysis of picture and sound quality, especially since one of the more interesting options is 4K HDMI recording. We'll do more with it when the code is done. That said, right now there's really only one affordable 4K HDMI recorder – Blackmagic's rack-mountable (but obviously not portable) Hyperdeck Studio Pro – and by the time others, such as Atomos's Shogun, appear at the end of the year, presumably Sony will have finalised the 7S's firmware.
Both GH4 and the 7S have shallow lens mounts. The micro four-thirds mount on the GH4, and the Sony E on the 7S, both have a short flange focus distance. A direct consequence of the lack of a viewfinder mirror, this is a particular advantage in that lenses of almost any type, including the enormously popular EF and even PL-mount movie primes can be used with an adaptor that needs include no expensive, sharpness-sapping optical components. Lens selection for the 7S is complicated somewhat by the need to cover a large full-stills-frame, 8-perf 35mm sensor, although the camera does offer the option of using only the APS-C sized area of that sensor.
Right now, only stills lenses, which can be difficult to work with in a motion picture context, and pricey options such as Schneider's Xenon series are likely to cover the full sized chip. However, since APS-C is similar in size to the 4-perf 35mm motion picture frame, lenses designed for movie work are more likely to be usable with the camera in this mode. The kit lens – a 24-70 F4 zoom – is fine but suffers infinitely-rotating servo focus and is less suitable for the more careful side of movie work.
Physically, the layout of the 7S is pleasant in an agreeably angular, slightly 1950s, classic sort of way. The engineering of the body – entirely metal, other than the flash card and battery doors – is of the quality one would expect from a camera in this price range, with reassuring sturdiness and drawing many positive comments about the tactile feedback on the four control wheels (two of which are assignable). Even the two doors which hide the HDMI and USB connectors and the two 3.5mm audio jacks (one powered mic in, one headphone out) are metal. The 7S is also, in the purely physical sense of the term, a compact camera, making the 5D Mk. III look like an absolute beast by comparison – the penalty of an optical viewfinder. The TFT display hinges out from the back of the camera for shooting high or low angles, permitting it to tilt up or down but avoiding the flimsy-feeling articulation common on some cameras – such as GH4 – which allows the display to be viewed from the front or side. The far sturdier vertical hinge arrangement on the 7S is, I think, a better compromise.
Sony supplied the 7S to me with a hot-shoe connected audio add-on. This is to be a £650 accessory, which seems steep inasmuch as Panasonic's more capable YAGH base for the GH4 is only about twice the value, but other than that option it's the single best audio provision on any stills camera. It provides mic or line input on XLRs, with optional phantom power, zero, 10 or 20dB attenuation, and manual level with physical controls. The onscreen metering on the camera is uncalibrated but could presumably be characterised with a signal generator and a bit of ingenuity. While the resulting package – mounted on the supplied bracket and particularly with heavy microphone cables – risks a degree of ungainly flimsiness, this is still superlative by competing standards.
It wouldn't be fair to publish all this effusive praise without including at least a couple of reality checks. The principal issue with the 7S, at least as anything other than a casual documentary camera, is power. The small NP-FW50 battery, of only 1600mAh capacity, seems to equate to only about an hour's operation when working with video, depending to an extent on the type and amount of video recorded and played back. This is entirely fair for a device of this type and no great imposition in a handheld scenario when dumping one battery and inserting another can be done quickly.
We can expect, however, that many users will choose to accessorise the camera for better handheld ergonomics, and no matter how simply this is done, it's inevitable that the camera will be attached to some sort of baseplate using its single 1/4” tripod thread. The battery door is about 43mm from the centre of that thread, and while some smaller baseplates might leave battery access free, some might not, making changes a real difficulty. The supplied audio accessory bracket, for instance, obscures the battery cover. This issue is exacerbated by the fact that Sony don't currently make a DC power option for the A7 series, so the camera can't be run from rig power. This situation could be greatly eased if the company were to offer a dummy battery with external power option, ideally with the lead exiting the dummy battery as far to the outboard of the camera as possible.
An uncharitable observer might also compare the recording and output options unfavourably with the capability of the sensor. The best signal coming out of the 7S is 8-bit 4:2:2 HDMI, with the internal options limited to various flavours of H.264, written to SD cards. The XAVC-S option provides a welcome bitrate boost if you have high spec cards, and should, to be fair, be reliable for all but the most demanding productions. Unlike the 5D Mk. III, however, there can't ever be a third-party raw option as the storage will never be fast enough. As such it's reasonable that there are no flat, log or otherwise low-contrast setups.
UPDATE The camera we were supplied with was a pre-production version that did not have S-Log 2 available in its menus. The productinon camera does in fact have this option
The only other issue is the practicality of that large sensor. With 4K options yet to go into the firmware, we don't know if the camera will shoot beyond HD resolutions in APS-C mode, but pulling focus on – effectively – Vistavision or 65mm film is not easy, especially considering the increased sharpness demands of quad HD resolution. The saving grace of the situation is the 7S' sensitivity, which the company has been keen to promote and might allow the use of smaller-than-average apertures to offset the focus issue. And sensitivity is probably the star turn here.
OK, fine, the highest sensitivity options – up to 400,000 ISO and beyond – are for advertising value and night-time military missions only. What's important, though, and the thing I've deliberately left to last, is that these comparisons I've been making to Canon's mighty third instalment of the 5D are not in any sense vainglorious. The 7S is, based on a side-by-side visual comparison at 51,200 ISO, at least a stop quieter, or if you want to look at it that way a stop faster, than the 5D Mk. III. It's probably usable, for that unmissable nature documentary or newsgathering moment, at that speed, and very acceptable at 12800, with extremely pleasant highlight handling as a result.
At least some of this is due to fairly aggressive noise reduction, but the bottom line is that this is a very good sensor. The fact that Sony has access to this level of sensor technology probably shouldn't surprise us if we consider the F series as a high-priced, early-adopter option. Seeing that R&D trickle down to this sort of level is more or less what we'd expect. Either way, what's absolutely certain is that Canon's high end now has significant company.
Update: the camera model we tested was a pre-production version. Some features were missing, including S-log.