Overview of the Technical Features of the Lumix DC-GH5s

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Even after the recent launches of the GH5 and the G9 Panasonic is still able to bring a host of new technology and innovation to surprise us in its latest model – the GH5s. The company has identified the G9 as its flagship stills camera, the GH5 as the leading hybrid – that’s excellent for both still and video work – and now the GH5s is the principle Lumix movie making tool. It takes on that roll with quite a number of new features that make it a real pro machine and one that will deliver the best possible video quality and massive range of situations.

The multi-aspect sensor

The Lumix GH5s uses a CMOS sensor that measures 17.3x13mm and which features a total of 11.93 million pixels. Despite the 4016×2760-pixel dimensions of the recording area and the 4:3 proportions of the sensor the largest still image will measure 3680×2760 pixels and will be in the 4:3 aspect ratio. The reason Panasonic has left us lots of unused pixels either side of the 4:3 aspect ratio on the horizontal dimension is so that well will be able to maintain much the same total pixel count when we switch to the 3:2 or 16:9 formats as these aspect ratios use pixels outside of the main 4:3 image area. The idea is that it will be easier to maintain the angle of view of our lenses as we switch formats, and that the cropping that would usually take resolution away to create a 16:9 frame, for example, doesn’t have to take place. The principle reason though is the maintenance of the focal length of the lens.

The multi-aspect characteristic of the way the sensor has been used will please videographers who like to use wide angle lenses, as it will preserve the width of their view as it makes the most of the covering circle of the lens whichever aspect ratio has been chosen for the project.

Dual Native ISO

Colour and contrast characteristics compared between the GH5 and the GH5s

The sensor in the GH5s has been designed to work in a wide range of conditions and to operate in low or bright light without loss of quality. Most imaging sensors have what is called a native ISO setting, which is usually around ISO 200 or 400. This means that it is at these settings users get the best quality, and the further away from native settings we go the more picture quality is compromised. This is the nature of all imaging sensors.

What makes the sensor in the GH5s different is that it has two native ISO settings – so we effectively get two sensors for the price of one. Well, we don’t quite get two sensors but we do get two different sets of circuitry that take receive the charge from the sensor pixel during exposure. One set of circuitry is designed for normal sensitivity and for working in normal conditions, and the other for high sensitivity and designed for working in low light.

The native ISO of the low sensitivity circuit is ISO 400, while the high sensitivity circuit produces a native ISO of 2500 – though in Vlog-L and HDR (Hybrid Log Gamma) Picture Styles that switches to ISO 800 and 5000. The idea is that the camera will work just like any other in normal conditions, but when faced with low light and high ISO settings it can switch a gear to produce very low noise images where other cameras struggle.

The benefits of such a system are quite obvious, as the higher sensitivity circuit produces clean images with full contrast, smooth tones and good colour saturation. The ability to produce good quality images and footage at high ISO settings means that users won’t have to light their subjects so much and ambient light sources can be used, creating more natural looking results – and less gear to carry around.

Noise at ISO 6400 compared between a JPEG from the GH5s (left) and a raw file from the Lumix DC-GX800

There are three settings for the dual ISO mode. Users can decide to use only the low sensitivity mode, only the high sensitivity mode or to allow the camera to decide via the auto mode. This mode switches between the two sensitivities using ISO 800 as the turning point for when the high setting comes into play.

Why the low pixel count?

The high ISO setting has been made possible by the lower pixel count of the sensor. As there are only 11.93 million pixels on the sensor in total they can be made bigger and more capable of gathering light. Bigger pixels can also hold more charge, hence the extra low ISO setting of ISO 160 and the extension to ISO 80. At the top end the standard top ISO of 51200 can be extended to ISO 204,800 – unheard of for a Micro Four Thirds camera. The reduced pixel count also makes read-out quicker so the effects of rolling shutter can be further reduced over the improvements we already saw in the Lumix G9.

JPEG file shot at ISO 51,800

As this is primarily a video camera the pixel count of 10.3MP is actually more than enough. We only need 8MP to achieve 4K resolution so the ‘spare’ pixels around that main 4:3 imaging area can be used to expand the recording surface to ensure we maintain 4K resolution when other formats are in use.

The only draw-back is that the sensor can’t manage 6K video as 18MP are required for that.

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