GH4: A filmmaker's perspective

By Andrew Reid:

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The biggest single advantage of the $1600 Panasonic GH4 is how complete it is straight out of the box and how affordable it is relative to professional cinema cameras. The GH4's video capability is well specified even in comparison to professional cinema cameras upwards of $10k. Although there are many reasons why outright specs are not the whole story, the GH4 has found favour in the professional filmmaking community because it's small and simple to capture 4K with. Consumers stand to benefit from this, but adding all the features of a professional video acquisition workflow to the GH4 takes some building blocks. The appeal of cameras like the Canon C300 at $15k to pros is that the blocks come integrated and ready to use out of the box. XLR audio interfaces, ND filters and a top handle are examples of features the GH4 needs to be outfitted with whereas often more expensive pro video tools like the Canon C300 often don't (although often cinema cameras like the Epic and Alexa, conversely, do).

However despite it being a bit of an apples to oranges comparison with the Canon C300, the GH4 benefits from a smaller size, smaller lenses, lower weight and the 4K image, with efficient long-running internal 4K recording, a 10bit 4K HDMI output and even a slow-mo mode all for $1600 whereas the C300 has none of the aforementioned imaging capabilities even at $15,000.

The GH4 is also the most beginner friendly of the current 4K interchangeable lens cameras. It has the lightest 4K file size footprint I have ever experienced in my own filmmaking work. The Panasonic GH4's internal 4K codec compresses video at 100Mbit/s compared to 500Mbit/s on the Canon 1D C, also a 4K stills camera in the DSLR-mould. This is a space saving of 1/5th and the quality trade off is less than you'd expect given the numbers, because the GH4's codec uses a more efficient H.264 IPB codec whilst the 1D C uses MJPEG, essentially a sequence of 24 JPEG frames per second stored individually. The IPB codec on the GH4 uses clever compression to synthesise space saving P and B frames in-between individual key "I" frames.

On a longer shoot it would be impractical and distracting to have the camera operator also take care of the data demands of the 1D C or Blackmagic Production Camera in 4K. If you also imagine your archival storage needs going forward 1 or 2 years it's easy to imagine the impact this will have on your overall costs. However if the ultimate quality 10bit ProRes 4K is required, this too can be bolted on via HDMI to a suitable recording device like the Atomos Shogun. For VFX heavy shooting, green screen or work involving heavy colour correction you'd notice the difference. For everything else you'd be hard pressed to find one, especially for 1080p delivery from the 4K source files.

Furthermore the GH4 is somehow able to compress so much data into so little space without any serious extra overhead on energy consumption and cooling. A typical professional 4K cinema camera like the Red Epic entails a long boot time and a fan to cool it due to the enormous data throughput. It requires more expensive media to record onto and more of it. It is heavier and ideally requires a crew for on-location shooting including someone whose responsibility is to manage all the data, whereas the GH4 is ready to shoot with instantly in the hands of a single crew member or owner-operator. It is of course absolutely silent with no fan and makes a great behind the scenes or POV camera if the main action is being shot on something higher end. In fairness though, the GH4 is not so much a 'replacement' for a professional cinema camera, more an additional option for the filmmaker which will be selected when the unique abilities of the tool are required by certain work. The simple fact that there's even a comparison to be made to Red or Arri says a lot about how far Panasonic has reached to connect with filmmakers.

Although 4K provides a more future proof image, in practical viewing reality and as of 2014 the image quality gain of 4K is as much about 1080p delivery quality as anything else. My preferred method of 1080p capture on the GH4 is to bypass the internal 1080p recording options altogether, instead scaling my 4K recordings to 1080p whilst editing. Doing so is as trivial as inputting 50% for clip size on a timeline in my editing software - yet the gain in quality over the internal 1080p is enormous.

Then there's the added creative flexibility 4K gives you. The 4K files grade better than the thinner 1080p recordings, with less banding and smoother gradients. You are able to zoom shots digitally in post whilst maintaining 1080p detail levels from 4K source material, rather than using Ex-Tele in-camera. Therefore you have much more freedom to reframe the action or a 'second shot' on a 1080p timeline, as if changing lenses after the event. In this way 4K is Ideal for interviews and live event shooting, not just cinema production.

The GH4 in 4K can roll for hours (in double figures) with the battery grip. Even on a single battery, single charge, you can record 4K on and off for 6 or 7 hours only rarely powering off while the a7S struggles to do a quarter of that time on a single charge.

Compared to the current 2014 Canon and Nikon line-up, shooting video on these now feels rather tame and dated by comparison to using the GH4. An enormous amount of catch-up is required by the 'big two' if they are to maintain the interest of video shooters.

Grading flexibility

Panasonic have included their own proprietary picture profiles - CineLikeD and CineLikeV on the GH4. Although these are the same picture profiles Panasonic use on their professional cinema cameras, they are not the LOG gamma curve profiles best known to filmmakers. Most professional colourists and editors will be more at home with S-LOG 2 on the a7S or Canon LOG on the 1D C but consumers will likely find it easier to work with CineLikeD and CineLikeV.

CineLikeD is the closest to a flat LOG curve (especially with contrast dialled all the way down incamera) providing maximum dynamic range, while the "V" flavour gives punchy contrast and colour straight out of the camera without any additional colour work in post.

You should choose CineLikeD for heavier grading and colour work on the GH4 but in my experience it does not offer the same flexibility in post as S-LOG 2 on the a7S. The upside is that dynamic range is actually still very good and comparable to the dynamic range offered by raw video on the 5D Mark III, yet with minuscule file sizes by comparison. With CineLikeD can do a much more simplified colour correction to bring the image to life compared to working with S-LOG 2 on the a7S, which really requires professional knowledge of grading software like Blackmagic DaVinci Resolve to get the most from.

Currently the GH4 and CineLikeD are supported by Film Convert Pro 2 which is popular with aspiring filmmakers, whilst the a7S and S-LOG 2 are not (yet). Especially with this plugin in your editing software, CineLikeD is the easier picture profile for inexperienced users.

External HDMI recording

The GH4 has the advantage of 10bit colour depth of over HDMI, making optimal use of Apple ProRes and Avid DNxHD codecs available on most external recorders. How big an advantage for 1080p is this? On the a7S the output signal is only 8bit, padded into a 10bit file. In theory 10bit recordings should offer more natural colour, less digital looking - but more-so colour accuracy depends on the performance of the sensor at the set ISO and the debayer of the raw sensor data to YUV for transport over HDMI. Clean, uncompressed HDMI despite appearance is not in fact a 'direct tap' on the sensor. Colour performance drops off significantly on the GH4's CMOS sensor above ISO 800, so is 10bit recording really an advantage in all circumstances? In practice I find the difference in quality to be usually extremely muted in almost all situations.

The quality of the GH4's internal 8bit 4K down-sampled to 1080p in post is more than a match for the 10bit 1080p over HDMI. Effectively this produces 1080p with 10bit luma levels for smoother gradation and 4:4:4 colour sampling, which helps to reduce aliasing or pixilation around highlights and hard coloured edges.

As far as 10bit 4K on the GH4 goes over HDMI, this will likely be different story. When the Atomos Shogun recorder is released later in 2014 I'll re-evaluate the situation because this is able to take 10bit 4K from the GH4, while the a7S will only output 8bit 4K. In theory the GH4 will have an advantage in 4K for colour critical shoots with a lot of subtle skin tones and for green screen / VFX heavy work compared to the a7S. But again a lot depends on the sensor. The a7S arguably has a superior one which provides a stronger, cleaner signal with less noise.

High end features for pros

A professional will always gravitate towards the best tool for a particular job rather than a single camera for everything. In this respect the GH4 has already carved out a place for itself with a small and light physical form-factor, small data footprint of the 4K recordings and small(ish) Micro Four Thirds sensor. The 2.3x crop sensor in 4K has a more manageable depth of field compared to 1.0x crop photographic full frame especially if you use a wider focal length on the smaller sensor to match the field of view of full frame (i.e. 25mm vs 50mm). Of course the GH4 has internal 4K recording which the a7S lacks entirely. The small size and internal 4K codec makes it ideal for projects involving MoVi-like gimbals, steadicams and aerial imaging from drones, where the final delivery of material will be 4K. This is true right up at the highest leagues of the filmmaking industry because higher end cameras don't share the same light footprint of the GH4. Especially in the case of aerial work, the extra resolution of 4K is an undoubtable advantage too over 1080p.

Although it's still a hybrid stills / video camera, ergonomics are far above a DSLR for video shooting which makes the GH4 a good low cost alternative to the ergonomically superior Canon C100 and C300. The many workarounds of DSLRs pushed a lot of pros to invest in the Cinema EOS line but with the GH4 the ergonomic gap has narrowed.

The small sensor and body have a few drawbacks too though, with poor results past ISO 1600 in dim conditions, noticeable compression on shadow areas again in dim conditions, noisier shadows at any ISO compared to the silky smooth a7S and a still quite severe rolling shutter skew in 4K relative to a more expensive cinema camera. The Blackmagic Cinema Camera has the advantage of zero rolling shutter skew, with terrible low light performance being the trade-off for that. It may not be the miracle at ISO 3200 that the a7S is but the GH4 produces a much cleaner 4K image at ISO 800 relative to the aforementioned Blackmagic. Horses for courses!

Pros looking to replace a traditional DSLR like the Canon 7D or Nikon D7100 with the GH4 will benefit from the more adaptable mirrorless mount, PL lens compatibility and the ability to get a close to Super 35mm cinema standard field of view with the Metabones Speed Booster. This adapter is now available in active Canon EF mount with support for optical image stabilisation and aperture control from the camera body. The GH4's built in EVF is also a significant advantage over a traditional optical viewfinder for video, purely for the fact it can be used! Mainly though it is the internal 4K recording and the low price of the GH4 which appeal so much to pros. They can invest in multiple bodies at this price and have long 4K recordings which do not pose as great a challenge to archive in the long term compared to ProRes and Raw.