[argyllcms] Re: Creating a camera profile with ColorChecker Passport Please Help
- From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
- To: argyllcms@xxxxxxxxxxxxx
- Date: Fri, 12 Jun 2015 18:01:01 -0700
On Jun 12, 2015, at 5:35 PM, Iliah Borg <iliah.i.borg@xxxxxxxxx> wrote:
You should be aiming for white
to reach something like 90% of full scale.
That would be too high, because of how the sensors and electronics behave
(blooming, non-linearities, pattern noise, pixel non-uniformity...). 70% is
the safety margin (-0.5 stops from clipping), unless the camera is full-well
limited at current ISO setting (like some Panasonics are). Generally
auto-exposure in center-weighted mode +0.5 EV compensation puts the target
right at the intended segment of the characteristic curve.
It's also worth noting that Iliah's suggestion is an excellent starting point,
but also not something set in stone. If you don't know and don't want to know
any better, follow Iliah's advice. If you want to know better so you can make
the optimal decision for your own circumstances (which will, almost certainly,
be rather close to Iliah's suggestion), you'll want to determine the linearity
of your actual camera...and that's easier written than done...
...but, after you've done so, you'll know if you don't need quite so much
headroom, or if you need to be even more conservative, or whatever, including
depending on how you're actually using the camera. Copy work can run right up
to the limit with no margin for error. If you're shooting for the Web, you
might as well give yourself lots of margin of error since simple geometry
eliminates so much noise giving you a vastly expanded effective dynamic range.
If you're shooting something between those extremes...you'll very likely come
to pretty much the same point as Iliah's suggestion.
b&
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