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 16:33:55 +0100
Neil
Wiliam wrote:
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
Why not try basICColor display,
it makes a 16 bit LUT profile which should work around the issue Apple seem
to have with profile, where the profile's response curve is "simple gamma"
*basICColor display 5, download demo:*
MAC:
http://mylicense.biz/getProduct.asp?proId=180&downloadKey=w8hz-pe6q-2n2s
WIN:
http://mylicense.biz/getProduct.asp?proId=181&downloadKey=uxr7-3m2p-bzx3
[full disclosure, yes I am a basICColor reseller]
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 1:02 PM Neil Snape via colorsync-users <
email@hidden> wrote:
> Coming back from holidays, all was well when comparing my iMac to the new
> BenQ SW270C. Until the auto update which occurred during the night. After
> the update I cannot trust what I am seeing on my iMac 27” 5K. Color and
> contrast are washed out, even the icons in the dock are not as before.
> Glad you pointed out where this is happening. Not sure there is an easy
> fix, as I am now chasing around with all monitors to get a color match even
> close.
>
>
>
> On 13 Aug 2019, at 05:21, 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
>
>
>
>
> Neil Snape
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