The following calibration settings were used for our review of the Samsung KU6300. They will work fine for most content, especially for watching movies. If you want to use the same settings for gaming, first select the 'Game' picture mode under 'Special Viewing Mode' and copy the rest of the settings.
Like on most other Samsung TVs, the 'Movie' picture mode is the closest to our calibration goal so it has to be picked first.
Under 'Expert Settings', we used a backlight value of 4 for our totally dark room. Adjust this value to your room lighting or to a comfortable level. High values won't deteriorate picture quality. Leave 'Sharpness' to 0 so no extra sharpness are applied to the picture.
Turn on 'Digital Clean View' when watching low quality content like cable TV and DVDs. Leave it off otherwise. The 'Auto Motion Plus' setting will smooth motion and add the soap opera effect (SOE). Use low custom values like 3-4 for slightly better motion without much of the soap opera effect. 'Color Tone' is set to 'Warm2' so to get that warm movie picture look. If you find the picture too dull or yellowish, use a colder value.
If you are planning to use a HDR enabled device (like an HDR UHD Blu-ray or a HDR compatible game console) or want to use the TV as a computer monitor with high details resolution like 4k@60Hz 4:4:4, you will need to turn on the 'HDMI UHD Color option for the port 1. If this option is not turned on, you won't be able to use the full bandwidth necessary to transmit all the information needed to display HDR or to display correctly the 4k@60Hz 4:4:4 resolution. Note that only on the HDMI port one that the 'HDMI UHD Color' can be used.
The following are the results of the white balance and colorspace calibration on our unit. You can try copying our values for these, but we don't recommend them as they vary per individual unit, so they might not be good, even for the same model and same size as the TV we reviewed. If you want to try them you will need to enter all values shown, as all of them are active at the same time. If you end up with worse picture quality, simply reset them to the default values.
Questions & Answers
Update: The service menu lists 55S6AUOVK as the panel, which means it is a Sharp. If you are happy with your TV, keep it. As you can from our testing here, the differences are usually minor and Sharp isn't necessarily worse.
Unfortunately this option has been removed with the 1142 firmware update. We don't know if Samsung has plans to bring it back in a future update.
Update 12/09/2016: With the newest firmware update (1150) the favorite channels are available again.
This is probably a CMO panel. If you have a universal remote you can confirm this in the service menu. To access the service menu (on a non-smart remote only) turn the TV off and press Mute followed by 1, 8, 2 and the Power button. Next to the 'Option' is a code, eg. 55A6AUOVK. The A (shown bolded here) indicates the manufacturer. If it is A it's Samsung, D is CMO, S is Sharp and L is AU Optronics.
Update:It is a Sharp panel.
Game mode doesn't support 4:4:4, only the PC mode does. You were not seeing 4:4:4, but it still looked much better than in PC mode with sharpness set to 0, which adds maximum softening.