[argyllcms] Re: Culling outliers from .ti3 input data before camera profiling

  • From: Ben Goren <ben@xxxxxxxxxxxxxxxx>
  • To: argyllcms@xxxxxxxxxxxxx
  • Date: Tue, 10 Jul 2012 15:45:43 -0700

On 2012-07-10, at 3:00 PM, Iliah Borg wrote:

> Dear Kamil,
>> we have big problems particulary with black patch, which give us very
>> weak black in resulting profile - far worse than we expect according
>> to measurement.
> One needs to consider adding black trap to any target.

Yes, and it's easy. Make a box, (optionally) line it with something black, and 
cut a small hole in one side. Black flock velvet works great as a lining, but, 
honestly,  even that is probably overkill.

> White patch similar to what Babel were using for their white target is also 
> extremely useful.

That would be Teflon (PTFE). A painfully cheap alternative is thread seal tape. 
Fold it over on itself a few times (a single layer is too translucent) and 
there you go. A dab of rubber cement will hold it in place. No, it's not 
especially durable...but it's not like the studio is a hostile environment in 
the first place, or that it's any big deal to replace.

Another alternative is Tyvek. It's only about 98% reflective (as opposed to 99% 
for Teflon) and its surface texture is more visible, but it's a lot more 
durable. And it's also dirt cheap...your local office supply store has 
envelopes made of them, and Canon sells large format printer banner media 
rolls. They put their standard matte coating (heavy on the FWA) on the one side 
for printing, but the reverse is pure, uncoated Tyvek. It's a great banner 
material, and the reverse side can come in quite handy.

While we're on the topic...a styrofoam cup also has a flat spectrum, though 
it's only in the 80% reflectivity range. Still, it beats the pants off any 
photographic white balance tool on the market. And I do mean that -- the cup 
will have a much flatter spectrum than anything short of Teflon (such as the 
Babel target or Spectralon), and it's the ideal level of reflectance. Get one 
that fits over your lens, and you can even sample the color of the entire 
scene. Or, put it in mixed light and get the color balance for each source in 
one shot, plus any gradation of blending.

I'm sure there're other types of plastic out there that have potential, but 
those three are the most common ones I'm aware of.



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