Color depth refers to the number of unique colors that a sensor can faithfully capture. Cameras with better color depth will demonstrate smoother transitions from one color to the next, and avoid "banding" in areas with subtle shading. (Blue skies are an example of where you might see color banding.)
More color depth is generally better, but you'll struggle to notice a difference between two cameras with less than 1 bit of difference. Color depth above 22 bits is considered excellent.
Want to learn more? Head over to our full glossary entry on color depth
Color depth test data courtesy of DxO Mark.GH4 test data on DxO Mark J3 test data on DxO Mark
Maximum effective ISO is an estimate of the highest sensitivity at which a camera can capture excellent quality photos.
Cameras with higher effective ISO will be better choices for indoor photography, night shooting, and indoor sports photography, especially if you intend to make large prints.
You can learn more at our glossary entry.
Maximum effective ISO test data courtesy of DxO Mark.GH4 test data on DxO Mark J3 test data on DxO Mark
Cameras with more dynamic range allow you to take photos with dramatic differences in highlight and shadow areas while retaining detail in both.
Think of a brilliant sunset on a rocky beach: Bright sunset in the background, with dark rocks in the foreground. High dynamic range means more of the extremes will be faithfully reproduced.
Dynamic range test data courtesy of DxO Mark.GH4 test data on DxO Mark J3 test data on DxO Mark
Excellent still image quality for its class; Fantastic, highly-detailed video quality; Superior video recording chops with 4K video (both Cinema 4K and Ultra HD); Responsive all-around performer with great AF performance and burst shooting; Rolling shutter is minimal with 60p and 30p video; Splash- and dust-proof magnesium alloy body; Built-in Wi-Fi with NFC.
High ISO performance not as good as some APS-C models (IQ drops quickly past ISO 3200); Overall still image quality not significantly better than the GH3; Sluggish buffer clearing with RAW files; Rolling shutter noticeable on 4K video; Not as compact as most mirrorless cameras.