Re: Possible ColorSync discontinuity bug introduced in OS 10.14.6 with display "r/g/bTRC" tags?
Re: Possible ColorSync discontinuity bug introduced in OS 10.14.6 with display "r/g/bTRC" tags?
- Subject: Re: Possible ColorSync discontinuity bug introduced in OS 10.14.6 with display "r/g/bTRC" tags?
- From: Neil Barstow via colorsync-users <email@hidden>
- Date: Wed, 14 Aug 2019 17:57:58 +0100
Hi William,
I hope you're keeping well
So, am I reading this right please?
An LUT profile would be OK and a "MATRIX" not, in this setting.
Is an LUT what you are calling "encoded as - - an array of points"
I guess a 16 bit LUT may be OK? I am just thinking about basICColor display.
Are you able to communicate with Apple about it - now John Zimmerer's gone
I've no idea who'd be in charge of Colorsync?
I saw a post from Steve about his NEC on the Adobe forum [compressed
blacks] and I think he may have been chatting with you about the issue?
https://forums.adobe.com/thread/2645572?prevContainerType=14&prevContainerID=4694
Best Regards, Neil Barstow
Imaging & Colour Management Specialist
http://www.colourmanagement.net
proud to be part of:
http://www.colormanagementgroup.com www.colormanagement.com
On Tue, Aug 13, 2019 at 4:21 AM William Hollingworth via colorsync-users <
email@hidden> wrote:
> I'm starting to get reports of a severe banding problem that seems to be
> related to the recent macOS 10.14.6 update which includes some (unknown)
> changes to ColorSync.
>
> I've duplicated this and what I'm seeing is that when a display profile
> has the r/g/bTRC "curv" tag encoded as a "simple gamma" value rather
> than an array of points (typically 256), then there can be a big
> luminance discontinuity between level RGB=0 and RGB=1 - depending on the
> gamma value. I'm using a simple grayscale test image in the Preview app.
>
> The canned "Adobe RGB (1998)" profile encodes the 2.2 gamma as a "simple
> gamma" and this issue is evident when selected as a display profile.
> However the "Generic RGB Profile" encodes gamma 1.8 this way also but
> the discontinuity isn't very obvious. So higher gamma values make this
> more obvious.
>
> Re-encoding the profile's response curve as an array of points instead
> of a single "simple gamma" value seems to avoid the issue. However it
> was perfectly OK in previous macOS versions.
>
> Is anyone else experiencing this issue? It looks like X-Rite encode
> their TRCs as an array of points regardless, so probably most people
> won't see it.
>
> Anyone at Apple aware of this?
>
> Thanks
>
> Will Hollingworth
>
>
>
>
> _______________________________________________
> Do not post admin requests to the list. They will be ignored.
> colorsync-users mailing list (email@hidden)
> Help/Unsubscribe/Update your Subscription:
>
>
> This email sent to email@hidden
>
_______________________________________________
Do not post admin requests to the list. They will be ignored.
colorsync-users mailing list (email@hidden)
Help/Unsubscribe/Update your Subscription:
This email sent to email@hidden