[argyllcms] Re: Creating camera profiles with Argyll

  • From: Graeme Gill <graeme@xxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 12 Nov 2008 02:00:31 +1100

Pascal de Bruijn wrote:
Though I'm curious about three things:
1. Ultra quality seems extremely slow... Much Much Much slower than
High quality... I've
had high quality compute in a minute or three... While I've had Ultra
quality running for
tens of minutes (after which I aborted). Is this normal?

Yes. "Ultra" can take an extreme amount of time (hours)
to create the B2A table.
Don't use it unless you have a specific reason.

The point why I was considering using ultra is to get 4096 entry
resolution instead of the 2048
which high quality produces. The general reasoning would be my camera
produces 12bit data,
which "means" 4096 entries.

Right, but you need to take into account that the 1D lookup
curves have 16 bit entry values, so the number of entries
has no specific relationship to the bit depth you are
working with.

2. The generated profile has a A2B0 table and a B2A0 table, but do I
really need both? I think
Nikon generates a high res A2B0 table, and a low res B2A0 table. Can I
do something similar
with Argyll?

You can choose a lower resolution or no B2A table at all
using the -b flag (ie. -bn). The B2A table is there so that round
tripping can be done on the device colorspace.

3. I also noticed Argyll identifies itself with 'argl', however all
other profiles I've
inspected so far use caps to identify themselves. Just of out curiosity, why
the lower caps?

No particular reason, that's just the tag I registered I think.
Many other tags are lower case.

Graeme Gill.

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