Digital BW, The Print

--- In DigitalBlackandWhiteThePrint@y..., "craig_spaulding" 
<craig_spaulding@y...> wrote:
> Jeff,
> 
> I have several questions re your transfer curves technique:
> 
> 1) Can the black and white points be set in Photoshop instead of 
the 
> scanner after the step-edge has been scanned? I work with a digital 
> camera and my scanner is marginal and I don't think the black and 
> white points can be set in the software.

I've had better luck setting the b/w points during scanning than 
setting in my image editing software (your results may vary).  I use 
VueScan as my scanning software and have found the histogram feature 
to be very good. (www.hamrick.com). I use Picture Windows as my image 
editing software because I think its curves/histogram feature is the 
best of any editing package (I also use it for a lot more reasons, 
but that's another post) (www.dl-c.com). I also have and occassionly 
use PhotoShop 6.0 
> 
> 2) Is this a technique for making a transfer curve or a curve that 
> is to be applied in an adjustment layer? Once the curve is made, 
can 
> it be applied either place?

Transfer curve and adjustment layer curves are essentially the same.  
They both map an input value (in what ever units) to an output 
value.  Because they use different units they are not directly 
interchangeable, but if you do the math you can create curves the do 
the same thing in both worlds.
> 
> 3) Is there a good method for going about modifying an existing 
> curve (like the Woolf)? Do you click on the appropriate step in the 
> step-wedge to find out where it is on the curve that step is, then 
> use the up/down arrow or change the numbers in the dialog box? If 
> so, is there a rhyme or reason for how much to change it to equally 
> space out the peaks, or, is it all trial and error. Or, do you just 
> focus on changing the general shape of the curve to space out the 
> peaks?
>
Here is an approach that I used to create my RGB Partitioned Workflow 
for the 1160 and MIS FS inkset (and modify the Woolf lumped 
workflow).  It works for me (your milage may vary)  It is not a 
complete cookbook and every nuance is not spelled out.  

1)  Print a quad purge image and scan using the procedure outlined in 
step #3 to determine the approximate reflective values (I use the 0-
100% scale) of each pure ink on the paper.   Crop the image to 
produce approximately equal areas of the 4 inks and white space.  The 
ink values determine the maximum "density" that can be
achieved by 
each ink alone and serve as a guide to when the next darker shade 
must be started. 
2)  Apply a starter RGB partitioned curve set to a 21-step wedge test 
image and then print.
[Note:  I use the step wedge posted in the Files section of the Yahoo 
Piezography3000 Group.  The file is piezmultisteps.psd.  It has 
excellent low (95-100%), medium (45-55%), and high (0-5%) brightness 
test areas to allow you to visually  evaluate and set these benchmark 
values. I initially used Paul Roark's curves he developed for the 
Piezography BW inkset and the Epson driver.]
3)  I scan the print with my HP-5370 scanner using VueScan.  VS 
settings are: 
* Crop = tightly set to only scan the narrow 21 step portion of the 
test image. Don't include any of the grayscale ramp or the portion of 
the 21 stepwedge with the light or dark separator lines.  My goal is 
to have 21 separate and narrow histogram peaks with little noise in 
between.   
* Color balance = auto levels. I use auto levels because it sets each 
RGB curve to the b/w points — neutral doesn't and white balance 
doesn't do this well.
[Note:  I don't care about the "color" of my
grayscale—all I'm 
interested in is the overall/combined brightness.]
* B/W points set to clip the 0% (255) and 100% (0) gray value steps 
to expand the range to the maximum.  That is, set the 0% gray value 
to the whiteness of my paper and the 100% gray value to the blackest 
black I can print with the inkset. 
* Scanning resolution = 150 dpi. 
* Number of passes = 4.  This reduces noise and increases peak 
separation, especially in the dark end.  The exact pixel alignment is 
not an issue with a stepwedge print.
* File color space = AdobeRGB
* Grain reduction = heavy.  This also seems to increase peak 
separation in the dark end.
* Tiff file type = 24-bit RGB
4) I open the Tiff file in Picture Windows and apply the Color|Curves 
function which combines a curve and histogram view of the pixels. 
[Note:  The PW Color Curve and grayscale Brightness Curve functions 
can both display the image value, lightness, or brightness of the 
image in the HSV, HSL or RGB color spaces, respectively.  I use the 
HSV color space because it does a good job of separating the image 
brightness component from the color components which I don't care 
about.  Image brightness in the RGB space is a weighted sum of each 
RGB color and overall not as useful.]
5)  I note on a worksheet whether each of the remaining 19 peaks 
needs to be moved lighter or darker and a relative amount.
6)  I then load and apply the RGB partitioned curve used to create 
the tight crop of the 21 step wedge to my test image and adjust each 
individual RGB curve (red=dark, green=medium, & blue=light gray), as 
determined in Step #5. 
7) I then save the new RGB partitioned curve under a different name.
[Note: When I get close to where I want the peaks to be, I open the 
Picture Windows RGB partitioned curve file (filename.cc) with a text 
editor and manually change the values (which are stored as 0-255 
values) ]
8)  I then print the test image.  
9)  Iterate until you are satisfied (or run out of paper or ink).