[argyllcms] Re: Can Eye-one Pro failure the calibration?
- From: Sam Berry <samkberry@xxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Tue, 5 Oct 2010 09:51:08 +0100
On 5 October 2010 00:16, Graeme Gill <graeme@xxxxxxxxxxxxx> wrote:
> Sam Berry wrote:
>
>> Anyone have any ideas for the false patch 2 reading? This is repeatable.
>>
>
> Is this with dispread ?
>
It is indeed.
dispread -d1 -c1 -v test and
dispread -d1 -c1 -V -v test
>
> One explanation would be that there is a synchronization problem.
>
> The code sleeps for 60 msec after changing a color (which at
> 50Hz or more, is at least 3 refreshes), but perhaps the delay
> with some cards, software and displays is longer than that ?
>
Most LCD displays have a 1-3frame delay anyway. Certainly a lot of s-PVA
panels have a 60ms delay before they even start to change, and then there is
settling time, which without overdrive could easily be another 50ms. As full
black-white-black changes cannot be overdriven, they will always need extra
time. The ISO response times are rated 10%-90%-10% full brightness. The last
10% each way takes a lot longer than the first 90%. Unfortunately I don't
have a storage scope or similar device to give you proper numbers. I do know
that PVA displays can take can take a long time (100ms+) to fall to black.
Given the 60ms delay through the frame buffers this is 160ms. CRTs also show
significant persistance after reverting from high brightness. The bulk is
dropped of after only a few ms, but a trail remains for several hundred ms.
A couldn't find much online in the quick time I looked but I found this:
http://www.xbitlabs.com/articles/monitors/display/lcd-guide_26.html
and
http://www.xbitlabs.com/images/other/response-8/p-gr2.gif
Given the small increase in total measuring time, I would suggest 200ms as a
more conservative margin.
>
> Another explanation would be that your display has some sort
> of "auto contrast" adjustment mode on, and it takes some seconds
> to react to image contents. Such a mode is (of course incompatible
> with color management.
>
The display doesn't have such a feature, but I'll try the same test on a
different display or 2 later today. And with a different sensor.
>
> What operating system version are you running on ?
>
Vista 32 SP2
>
> Graeme Gill.
>
>
Sam Berry
www.satsumatree.co.uk
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