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Inner Enlightenment
On the inside, the GH4 is quite different from the GH3 because just about everything has been either up-graded or tweaked – sensor, processor, shutter, AF system, metering, the WiFi module and more.

The sensor is again a 4:3 LiveMOS device with a total pixel count of 17.2 million and an effective count of 16.05 million, but it’s actually a new imager with an extended dynamic range, increased sensitivity range (equivalent to ISO 200 to 25,600) and a faster read-out speed of up to 200 MB/second. It’s supported by a new quad-core processor – called the ‘Venus Engine 9 AHD’ which is really the star of the show given it’s got some heavy-lifting to do, not just in the video department, but also with the GH4’s up-rated stills capabilities. The maximum continuous shooting speed increases to a rapid-fire 12 fps (with the AF/AE locked to the first frame) and a still handy 7.0 fps with continuous AF adjustment. The burst length with RAW capture increases to 40 frames and 100 frames for maximum quality JPEGs.

The new processor is also behind the GH4’s autofocusing system which still relies solely on contrast-detection measurement, but gets a new control element called ‘Depth From Defocus’ or DFD. This works on data stored in the camera for all the Lumix G lenses, enabling their out-of-focus characteristics – derived from grabbing two frames in quick succession as the lens is focusing – to be used to determine the subject distance and this calculation is then referenced to the contrast-detection AF’s measurement. The lens is then driven pretty well directly to the focusing distance with just minor fine-tuning at the end just as happens with phase-difference detection AF. This increases both the speed and the reliability of the system so it’s particularly beneficial to the continuous AF and focus tracking operations. When a new model of lens becomes available, its out-of-focus characteristics will be automatically uploaded to the GH4 body when it’s first fitted. Additionally, the number of focusing points increases from 23 to 49 – in a 7x7 pattern – which gives a much wider coverage, and the low light sensitivity extends down to -4.0 EV (at ISO 100). A single zone can be adjusted to any desired size to determine selectivity or, alternatively, clusters of nine zones can be selected, but more usefully, there’s a ‘Custom Multi’ mode which allows the number of points and how they’re shaped to be freely adjusted to suit the subject. Manual focusing is assisted by a magnified image section (which is easily moved around the frame), a simple distance scale and now the much-demanded focus peaking display (selected from two levels and three colours, but yellow and high is particularly effective).

As on the GH3, the GH4 has both a conventional focal plane shutter and a sensor-based shutter which is referred to as an ‘electronic shutter’, although the former is still electronically controlled. Its top shutter speed is lifted to 1/8000 second and the maximum flash sync speed to 1/250 second. Additionally, Panasonic now rates the shutter assembly at 200,000 cycles. The sensor shutter offers the advantages of completely silent operation and no lag so it enables a continuous shooting speed of 40 fps with JPEG capture.

The GH4’s built-in flash is supplemented by both a hotshoe and PC terminal, but as on the GH3, it’s a pretty capable unit in its own right. In addition to the standard modes of auto, fill-in, red-eye reduction, slow speed sync and second curtain sync, it also allows for manual control (down to 1/128 power) and can served as the commander for a wireless TTL flash set-up. Flash compensation is available over a range of up to +/-3.0 EV, and the angle of coverage matches the 12mm focal length in the Micro Four Thirds format (effectively 24mm). Incidentally, all exposure settings can be adjusted in either one-third or full stop increments.

Light And Shade
The GH4 gets Panasonic’s latest 1728-zone multi-pattern metering system and the alternative metering methods are centre-weighted average and spot.
The standard set of ‘PASM’ exposure modes are supplemented by program shift, an AE lock, up to +/-5.0 EV of compensation (applied in 1/3 EV increments) and auto bracketing. But the GH4 goes without any manually selectable subject/scene programs – which makes sense on a camera of this calibre – although the ‘iAuto’ modes have automatic scene selection which choose from ten possible scenarios. The other ‘iAuto’ components include backlight compensation, dynamic range expansion processing, sensitivity adjustment, focus tracking, face detection and recognition, red-eye removal and ‘Shading Compensation’ which corrects for lens vignetting. There’s also an ‘i.Auto+’ mode which provides limited manual adjustments for depth-of-field, brightness level (i.e. exposure compensation) and colour balance. These are done via touch control using on-screen sliders.

The key ‘i.Auto’ processing functions are also available for use with the ‘PASM’ modes, including dynamic range expansion processing – called ‘Intelligent Dynamic’ – long exposure noise reduction and ‘Intelligent Resolution’ processing. ‘Intelligent Resolution’ can be set to Low, Standard or High, and it detects outlines, textures and areas of soft gradations, subsequently enhances the edges to increase the definition and the appearance of sharpness. Interestingly, the GH4 inherits the Highlight/Shadow adjustment control from the Olympus OM-D cameras, but with some added capabilities such as being able to save three adjustments as well as access a number of presets. It works in the same way as on the Olympus cameras – i.e. like a simplified version of Photoshop’s Curves – with adjustments applied to a tone curve displayed in the monitor screen. The front wheel tweaks the highlights while the rear dial works on the shadow.
Still on managing exposure and contrast, there’s a multi-shot HDR capture mode with the choice of an Auto setting or three manual settings for exposure adjustments of +/-1.0 EV, +/-2.0 EV and +/-3.0 EV. There’s also an auto align function.

The choice of ‘Creative Control’ special effects increases to a dizzying 22, but the choice of ‘Photo Style’ picture presets remains at six. The five colour presets have adjustable parameters for contrast, sharpness, colour saturation, hue and noise reduction. The Monochrome preset has a colour tone adjustment (from sepia to cyanotype) and a set of contrast filters (i.e. yellow, orange, red and green). One customised ‘Photo Style’ can be created.

The white balance control options are the same as those provided on the GH3 and comprise auto correction supplemented by five presets and four custom measurements (increased from two) plus manual colour temperature setting from 2500 to 10,000 degrees Kelvin. Fine-tuning is available along either the blue-to-amber or green-to-magenta ranges with auto bracketing in one or the other performed over a sequence of three frames.

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Speed And Performance
Panasonic supplied one of its new Gold-series Speed Class 3 SDHC cards so we could record 4K video with the GH4, but for our speed tests for still capture we reverted to our reference 64 GB Lexar Professional SDXC card which is a UHS-I device (but Speed Class 1 just to confuse things).

With continuous AF/AE operating, the GH4 fired off 75 JPEG/large/fine frames in 10.71 seconds which represents a shooting speed of 7.0 fps. We just chose 75 frames as an arbitrary number, the camera would happily have motored on a full speed to the buffer’s maximum of 100 frames. With the AF fixed to the first frame, a burst of 80 frames was rattled off – and that’s what it sounds like – in 6.625 seconds so the shooting speed was 12.07 fps. While these numbers are impressive in themselves, just when you’d need bursts of 75 or 80 frames is debatable, but then not much is going to get away from 12 fps!

While much of the hoopla surrounding the GH4 has been about its remarkable capabilities as a video camera – and they are undoubtedly remarkable – it’s also a very fine stills camera too. Both Olympus and Panasonic have conclusively proved the naysayers wrong with the image quality that they’re now extracting from Micro Four Thirds size sensors. Certainly with the Lumix GX7 and both the OM-D E-M1 and E-M10 models we’ve seen performances that at least match that of comparable ‘APS-C’ CSCs or even do better in some areas… including, interestingly, sharpness. The GH4’s maximum quality JPEGs are a joy to behold – beautifully detailed, richly coloured and with a surprisingly wide dynamic range (without resorting to any form of expansion processing). Good detailing is held in both the deeper shadows and the brighter highlights. Colour reproduction is accurate across the spectrum and the camera handles both subtle shades and fully saturated tones with equal aplomb.

Noise just isn’t an issue up to ISO 1600 – very good for an MFT camera – and only starts to become noticeable at ISO 3200 as the reduction processing starts to diminish definition. You can still shoot at ISO 3200, but the higher sensitivities become increasingly restrictive in terms of just how large these images can be reproduced. The ISO 25,600 is probably a last resort, assuming there is just no other way of getting more light into the camera.

The new AF system is so fast the image simply snaps into focus in the EVF or on the monitor screen and we didn’t encounter any situation where it wasn’t absolutely reliable. Whichever way you decide to operate the GH4, it’s fast and efficient, but the touch screen controls are particularly well presented. However, having the WB, ISO and exposure compensation buttons situated close to the shutter release makes them easy to access in a hurry. The WiFi functionality is significantly enhanced by the provision of NFC which makes for a fast hook-up with mobile devices and the remote control capabilities facilitated through the Image App could be particularly useful when the camera is in a video rig.

The Verdict
There’s really nothing for it but to give Panasonic a loud round of applause for the Lumix GH4. It’s a masterpiece and it will undoubtedly have rivals banging on the doors of their product planning departments, demanding action. On the video side, the GH4 is a stroke of genius, even if you take the 4K recording out of the equation (but at least it’s ready and willing). The combination of capabilities, compact size and sheer affordability is unmatched anywhere else in the video world. Even throwing the bulky Interface Unit into the mix – which essentially turns the GH4 into a fully-fledged pro video camera – doesn’t alter the equation in terms of capabilities-versus-mobility. As a still camera, the GH4 is equally accomplished, although perhaps not as precociously talented here as its video alter-ego. Nevertheless, the combination of capabilities, usability and performance is a highly desirable one. And even if you’re resisting video’s siren song right now, if 4K really takes off you won’t be able to resist and then you’ll be thankful for Panasonic’s foresight. Ironically though, while the GH4 may be the most advanced hybrid CSC on the market, it also has one of the most traditional of control layouts so it still looks, feels and works like a D-SLR.

So, just about any way you look at it, the GH4 is the answer.