Comment 0 for bug 1749420

- Ubuntu 18.04 (with updates as of 14 Feb 2018).
- Laptop: Asus Zenbook UX303
- CPU: Intel i5 4210U
- Graphics: Intel HD 4400

Problem description: Colour artefacts and banding in all apps. Graphics, photos and videos display as though the colour range is improperly configured.

See this photo of a 1080p video taken with a camera (poor quality, but illustrates the issue): https://ubuntucommunity.s3-us-east-2.amazonaws.com/original/2X/c/c8f266715226953c6a77db6367ff9b7895784e35.jpg

Look at the sky’s light colours. They display with smooth gradients on Ubuntu 16.04, but as the photo illustrates 18.04 seems to display the video with a smaller range of white colours. This is the most apparent with either very dark or very light colours. Even on window titlebars the banding is visible (displayed as lines with different shades of grey/black).

Compared with a PrtSc shot of the same image:
https://i.imgur.com/VkOSCaQ.png

The artefacts are not present on PrtSc shots that are taken on Ubuntu 18.04 but viewed on a different system (16.04 and Windows).

Installing a previous kernel version fixes the issue completely. I used UKUU Update Utility to install kernel 4.4 (the same that I use in Ubuntu 16.04 without issues) and upon a reboot with 4.4 running on 18.04 everything displayed smoothly. So this indicates that the system might be using a sub-optimal colour depth with the newer kernel?

ProblemType: Bug
DistroRelease: Ubuntu 18.04
Package: linux-image-4.13.0-32-generic 4.13.0-32.35 [modified: boot/vmlinuz-4.13.0-32-generic]
ProcVersionSignature: Ubuntu 4.13.0-32.35-generic 4.13.13
Uname: Linux 4.13.0-32-generic x86_64
ApportVersion: 2.20.8-0ubuntu10
Architecture: amd64
AudioDevicesInUse:
 USER PID ACCESS COMMAND
 /dev/snd/controlC0: ystein 1344 F.... pulseaudio
 /dev/snd/controlC1: ystein 1344 F.... pulseaudio
CurrentDesktop: ubuntu:GNOME
Date: Wed Feb 14 11:25:43 2018
EcryptfsInUse: Yes
HibernationDevice: RESUME=UUID=d0bae648-a4d8-454c-b9fc-4cc04874d6c1
InstallationDate: Installed on 2018-02-12 (1 days ago)
InstallationMedia: Ubuntu 18.04 LTS "Bionic Beaver" - Alpha amd64 (20180210)
Lsusb:
 Bus 002 Device 001: ID 1d6b:0003 Linux Foundation 3.0 root hub
 Bus 001 Device 004: ID 8087:07dc Intel Corp.
 Bus 001 Device 003: ID 064e:9700 Suyin Corp. Asus Integrated Webcam
 Bus 001 Device 002: ID 046d:c52b Logitech, Inc. Unifying Receiver
 Bus 001 Device 001: ID 1d6b:0002 Linux Foundation 2.0 root hub
MachineType: ASUSTeK COMPUTER INC. UX303LA
ProcFB: 0 inteldrmfb
ProcKernelCmdLine: BOOT_IMAGE=/boot/vmlinuz-4.13.0-32-generic.efi.signed root=UUID=25279d7b-cc8a-4fee-9088-cfc69607cbca ro quiet splash vt.handoff=1
RelatedPackageVersions:
 linux-restricted-modules-4.13.0-32-generic N/A
 linux-backports-modules-4.13.0-32-generic N/A
 linux-firmware 1.170
SourcePackage: linux
UpgradeStatus: No upgrade log present (probably fresh install)
dmi.bios.date: 09/01/2014
dmi.bios.vendor: American Megatrends Inc.
dmi.bios.version: UX303LA.204
dmi.board.asset.tag: ATN12345678901234567
dmi.board.name: UX303LA
dmi.board.vendor: ASUSTeK COMPUTER INC.
dmi.board.version: 1.0
dmi.chassis.asset.tag: No Asset Tag
dmi.chassis.type: 10
dmi.chassis.vendor: ASUSTeK COMPUTER INC.
dmi.chassis.version: 1.0
dmi.modalias: dmi:bvnAmericanMegatrendsInc.:bvrUX303LA.204:bd09/01/2014:svnASUSTeKCOMPUTERINC.:pnUX303LA:pvr1.0:rvnASUSTeKCOMPUTERINC.:rnUX303LA:rvr1.0:cvnASUSTeKCOMPUTERINC.:ct10:cvr1.0:
dmi.product.family: UX
dmi.product.name: UX303LA
dmi.product.version: 1.0
dmi.sys.vendor: ASUSTeK COMPUTER INC.