[argyllcms] Re: Number of patches - well behaved printer?

  • From: Rishi Sanyal <rishi.j.sanyal@xxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Wed, 23 Feb 2011 15:48:46 -0800

Thanks Iliah. Admittedly I know nothing about film recorders, so my
concept of what you did 'outputting 5000 patches onto film directly'
is very limited!

I don't understand how it's not essential to have Dmin & Dmax mapped
to black & white when shooting a target on film. When building a
'scanner' profile (not a 'camera' profile), 0,0,0 & 255,255,255 (on an
8-bit scale) are literally mapped to the darkest and lightest patches
when I use LPROF to build a profile for my Velvia film using Wolf
Faust's 35mm targets (288 patches, IT8 chart). Are you not building a
'scanner' profile? I know for 'camera' profiles profiling packages
don't require the black on the chart to be 0,0,0 from your camera &
white to be 255,255,255 (in fact, that's really hard to do since
typically your camera has a much wider dynamic range than that
possible from imaging a reflective target)... because all it's doing
is building a 3x3 matrix, no?

For that matter, how does Wolf Faust even create the IT8 targets on
positive film? The black on the grayscale ramp is pretty much Dmax &
the white is Dmin... perhaps I should ask him, but let me know if you
know :)

Many thanks!

On Wed, Feb 23, 2011 at 3:21 PM, Iliah Borg <ib@xxxxxxxxxxx> wrote:
> Dear Rishi,
> On Feb 23, 2011, at 5:43 PM, Rishi Sanyal wrote:
>> Iliah,
>> You mention: "Argyll makes excellent profiles for colour negative
>> films, something no other profiler can do (export DNG from vuescan and
>> bring it to RPP - and you will see)"
>> Do you have color targets shot on negative film (I think Fuji used to
>> once offer a negative film target) or do you shoot targets yourself on
>> film?
> For daily outdoors use I shoot ColorChecker Passport - it is good enough to 
> put the colour response into the ballpark. In the studio I prefer 
> ColorChecker DC. For film simulation profiles I used a recorder to output the 
> targets (about 5000 patches) onto the film, directly. Those are, of course, 
> film simulations and very generic, measured right from the film - while for 
> normal use one wants to scan and make film+scanner profiles. Some of the 
> simulation profiles done with Argyll  are incorporated into RPP.
>> If the latter, ideally you'd want the blackest black & the
>> whitest white on the grayscale gradient to map to the lowest exposure
>> (clear film for a developed negative) & highest exposure (Dmax for
>> developed negative) possible on the film, correct?
> Actually this is not essential for negative profiling. Most important as far 
> as my experience goes is to get 18% grey to be exposed and developed 
> sensitometrically correct. That is to expose using a spotmeter as an 
> indicator, bracketing +/-2 stops with half a stop difference. Now, if you 
> want very wide target all you need is to make a composite of 3 exposures, 
> centre, +2, and -2. Such a target covers the dynamic range of the best 
> negative film I ever encountered.
> --
> Iliah Borg
> ib@xxxxxxxxxxx

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