Digital BW, The Print

I would take step 26's reading, do the linearization, print the step wedge
again (linearised this time) and check the separation.  Only then would I
make any sacrifices...Just a thought.  The trickier issue is when,
unlinearised, step 25 measures darker than 26!


> From: ldina <lbdina@...>
> Reply-To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Date: Mon, 24 Jan 2005 20:07:40 -0000
> To: <DigitalBlackandWhiteThePrint@yahoogroups.com>
> Subject: [Digital BW] Re: IJC/OPM - DMax "darker than the eye can see".
> 
> 
> 
> John,
> 
> I had the same question, and here is how I resolved it along with my
> reasoning. 
> 
> I use L* readings from my Eye One instead of using density units.  L*
> readings, which are plotted on a linear scale, should show roughly
> the  same difference between steps on a linear profile.  If a glossy
> paper has a paper white of L* 95, and deepest black of L* 6, then
> there is a total difference of 89 L* units.  Divide this by 26 (the
> number of steps in the IJC linearization routine) and each step
> should be differ by about 3.4 L* units.  That helps me better put it
> into quantitative terms.
> 
> When step 25 and 26 both look the same by eye, I take readings with
> my EyeOne.  If step 26 reads 6.0 and step 25 reads 6.3 or 6.4, they
> are so close as to be nearly indistinguisable both by eye and by L*
> readings.  They are both essential black, and looking at a desired
> difference of 3.42 helps me put it into perspective.  In this case, I
> will select 25 as my ink limit.  My reasoning is that if I use 26,
> there is essentially no tonal separation between 25 and 26, which
> forces IJC to make more extreme adjustments to give me a linear tone
> scale.  Getting closer to being linear before asking IJC to do its
> math will give me smaller adjustments.  I seem to get a better
> profile that way and don't notice any loss of black.
> 
> If step 26 reads L* 6.0 and step 25 reads 7.0, tonal separation is
> more substantial (even if it may still be tough to see by eye) and I
> would probably choose 26 as my ink limit.  If the difference is 1 or
> greater, I always go with the darker test patch.
> 
> Maybe not totally scientific, but it seems to make sense and works
> for me.
> 
> Lou