[argyllcms] Re: White Point
- From: Elle Stone <ellestone@xxxxxxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Mon, 21 Sep 2015 06:31:06 -0400
On 09/20/2015 10:11 PM, Ben Goren wrote:
On Sep 20, 2015, at 5:15 PM, Hening Bettermann <hein@xxxxxxxxxxxxx> wrote:
I have earlier used -am, but -aX gives better Delta-E values.
But if you're making a profile from a commercially-available reflective chart,
-as -qm is your best bet.
Assuming the raw processor is outputting interpolated target chart data
without applying its own TRC to the data, then "-as" assumes that the
sensor (or sensor + internal camera "pre-processing" before writing the
raw file) responds nonlinearly and also differently in each channel.
Is there a reason to think Hening's camera is saving significantly
nonlinear results in the raw file?
Are there enough points on the target chart to accurately model any
presumed non-linear response of the "camera plus internal preprocessing"?
Some raw processors (digiKam's raw processor) do apply a tone curve over
which the user has no control, in which case "-aS -qm" or "-aG" would
seem to be a better choice.
Low deltas look really nice as they are printed to the terminal. But I
think it's pretty important to also plot the xicclu graph and ask if the
resulting curves make sense.
Elle
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