Digital BW, The Print

Hi Nick.

"Does the OPM brightness slider work like the aim slider?"

The AIM slider in IJC applies a single point gamma adjustment to the 
linearization.  So, if you move the slider to -2, for example, the 
midpoint of the scale will be made lighter.  The white and black 
points are held constant.  The adjustments are heaviest in the middle 
of the tone curve and become smaller and smaller as you move toward 
the end points.

From my experimentation, it appears the contrast slider in OPM acts 
very much like an "S" curve in Photoshop.  The end points appear to 
remain fixed.  Moving the slider to the right increases contrast (ie, 
brightens the 1/4 tones and darkens the 3/4 tones).  Moving the 
slider to the left lowers the contrast (darkens the 1/4 tones and 
lightens the 3/4 tones).  

I'm not 100% certain about the brightness slider in OPM, but visually 
it seems to hold the end points constant and brighten all the points 
in between, much like the gamma slider in IJC.  I loaded the 26 step 
grayscale in OPM to experiment.  I used a piece of cardboard to cover 
steps 1-25 on screen so only step 26 was visible.  Moving the 
brightness slider from one extreme to the other showed no visible 
change in step 26, at least to my eye.  I did the same with step 1 
and saw no difference.  Of course, steps 2-25 do change as you adjust 
the slider.  I'm not sure if this works exactly the same as the gamma 
slider in IJC or not.

We'd have to ask Joe Berndt to be absolutely certain.  

At present, IJC only allows a single point gamma adjustment with the 
slider.  I'm not sure I would need or want more ~ I'd have to think 
about it some.  I'd probably prefer to keep the profile simple and 
linear, then make any desired tonal adjustments in PS.  If I have an 
accurate soft proof preview in PS and make my adjustments there, I 
have fewer variables to contend with and fewer ways to screw up my 
print.  

(Actually, you CAN build and save a non-linear profile in IJC if you 
wish and make any adjustments you want.  You would set ink limits, 
adjust curves, etc, as always.  Print a target for linearization and 
read with a densitometer or spectrophotometer, entering the data in 
the linearization window.  Once you have a raw curve shape you like 
(based on your density readings), switch to the Ink Shapes tab and 
click the Save button.  You will be prompted as to whether you want 
to save without linearization.  If you say yes, IJC will skip the 
Auto linearization and let you save your raw data as the final 
profile.  If using Save from the linearization tab, IJC always 
applies an auto-linearization to your raw data.)

Regards, 

Lou


--- In DigitalBlackandWhiteThePrint@yahoogroups.com, "Nick H. Nugent" 
<nghin@p...> wrote:
> 
> Hi Lou,
> 
> Yes. The entered linearization data is fixed. It's the aim slider 
> value that is stored in the profile that tells OPM how to adjust 
the 
> output gamma.
> 
> Peter has a question about the exposure slider which I haven't 
played 
> with much at all. Does the OPM brightness slider work like the aim 
> slider?
> 
> I asked Joe Berndt about the possibility of adding a way to tweak 
the 
> aim curve like a Photoshop curve. The OPM constrast slider gives me 
> additional constrast but I like the characteristic of Paul Roark's 
> curve for the 1160/FS/Mild-EEM combination. I will boost the OPM 
> constrast curve and compare it with Paul's curve to see how close 
> they are. But being able to tweak the aim curve will make it much 
> easier to fine tune a profile for a particular type of image.
> 
> --nick
> 
> --- In DigitalBlackandWhiteThePrint@yahoogroups.com, "ldina" 
> <lbdina@c...> wrote:
> > 
> > Nick,
> > 
> > That is my experience.  If you want to lighten the midtones in 
your 
> > profile, just move the slider a few points in the minus 
direction.  
> > Your raw data is still plotted on the curve based on the L* or 
> > density units you originally entered (unless you click the clear 
> > button, in which case you would need to reenter the data).  So, 
the 
> > green curve represents the absolute value and spacing between 
each 
> > of the 26 steps after IJC performs auto linearization.  All you 
> > need to do is save your profile after moving the gamma slider and 
> > you will have a finished, linearized profile.
> > 
> > Lou