Image Quality: Panasonic GH4

Dynamic range

The GH4's sensor is capable of an impressive amount of dynamic range, especially at low ISO settings. This means it's not uncommon to find plenty of additional tonal information in the shadow region of the image, if you wish to pull it back into the picture. We wouldn't recommend using ISO 100, since it appears to clip the maximum Raw values it can record (reducing dynamic range).

Here you can see an ISO 200 shot exposed until the brightest tones are nearly clipped. We've then lifted the shadows and brightened the image to show how much additional information is available. Although this is probably more of a push than you'd want to include in this particular image, it does give an idea of how much processing latitude the GH4's files have.

ISO 200, 1/200th seconds, F6.3
Processed in Adobe Camera Raw
Exposure: +1.3EV, Highlights -100, Shadows +100, Blacks +62
100% crop. This region has experienced around a +4EV push and still shows usable detail (though with luminance noise beginning to appear).

The darker left-hand side of the image has received around a +4EV push yet the detail is still usable. Using the lowest available ISO and setting the exposure based on the clipping point of the file is the best way of maximizing this processing latitude.

This is a very good performance and within around 1/3EV of APS-C rivals. It can't match the a7S (which itself is a little behind the best in class), but it's a considerable step above what was possible just a few years ago. It means, for instance, that you can shoot images such as the one below, where the foreground shadow regions have been lifted and the highlights softened, to give an 'as-remembered' representation of a high-contrast scene (compare with the original JPEG and you'll see the sky hasn't been exaggerated).

Raw file processed with Adobe Camera Raw, Shadows +100, Highlights -54. Tone curve adjustments to lift the mid-tones and color-specific hue, saturation and luminance adjustments to get the sky color to better match the JPEG. The only selectively-applied effect is a 'warming' of the foreground (+20 on the Blue/Amber axis) to correct for overly blue-tinted shadows. Click here to download the original Raw file.

Low light image quality

Here we look at the GH4's image quality in extreme low light. Here we compare it to the only other high-end, 4K-capable stills/video hybrid on the market - the Sony ILCE a7S - but it can also be used to assess the camera's IQ in its own right.

When it comes to low light, the GH4 simply can't compete with the a7S, but then nor can most other cameras currently on the market. Both cameras have sensors close enough to the state-of-the-art that there's no way the GH4 can make up for the difference in sensor size, which should give the Sony a 2EV advantage, in low light.

The GH4 does pretty well in this situation, producing pretty clean images up to around ISO 3200. Sensitivity setting above this can still be used with application of a touch of noise reduction (not applied in this comparison).

If matched for depth-of-field and shutter speed, you would generally expect the GH4 to be able to match the a7S (since it means stopping the Sony down by 2EV and increasing the ISO by the same amount). However, the a7S's sensor is one of the best low light performers on the market, so you can see it actually out-performs the GH4 by around one stop more than you would generally expect, meaning that the GH4's performance is comparable to the a7S using a sensitivity setting three stops higher.

Overall image quality

Panasonic's JPEG engine has improved significantly in recent years, producing much more pleasant out-of-camera images without the color/white balance inconsistency that would sometimes trouble its predecessors. Generally we found we preferred the out-of-camera colors to those we got when we opened the images in Adobe Camera Raw.

At default settings sharpening is a little aggressive, which can present hard-edged detail as jagged edges. Thankfully the range of sharpening offered by the JPEG engine is quite subtle, so you can dial it down just a little, in an attempt to render the detail better and without everything becoming too soft.

Default Sharpening Sharpening -2

In this example, we've re-processed the same image from Raw. As you might (just) be able to see, the images on the right have less prominent jagged edges to the detail on the playing cards but without any significant cost to sharpness in the low-contrast greenery.

The other issue, in shadow regions of low ISO images in particular, is noise reduction. Here we have a comparison between one of the camera's JPEGs (shot in Raw, then processed in-camera to lift the shadow, using iDynamic level 1). As you can see, a lot of the fine detail is lost, but is clearly visible in Adobe Camera Raw conversion (that has also had its shadows lifted, along with a tone-curve adjustment to boost contrast.

Raw images re-processed in camera: iDynamic Level 1 Adobe Camera Raw conversion, Highlights -25, Shadows +67, small tone-curve adjustments.

The point to this example isn't so much that the ACR version has greater contrast (which it does purely because we adjusted the contrast to draw detail out of this specific image), but that it has much finer detail which has been heavily smoothed in the camera's JPEG.

The pleasant JPEGs also mean that the ability to re-process Raw files in-camera is rather useful. Combined with Wi-Fi it allows you to tweak the brightness, contrast and a variety of other settings of your favorite images, if you want to fine-tune them before uploading them to a social network or e-mail them to friends.