I guess I have to jump in here.
--
There are a lot of little gotcha's in making accurate targets -- or even what "accurate" means.
The first issue is that 8-bit files are just that 8-bit -- values from 0 to 255. So talking about
percents (i.e. K-values) is just an approximation. With 5% steps like the 21-step its
close enough to not worry about. But trying to do 1% steps is full of potholes.
Richard's text reference file shows all the fractional steps -- 0, 2.55, 5.1, 7.65, ...
but when made into the 8-bit tif target file all the fractions are dropped off -- there are
no fraction values in an 8-bit file. So the sequence becomes 0, 2, 5, 7, ... which is
nowhere near even. Some jumps are 2 and some 3. That's a 50% size difference.
To get reasonable 1% steps you have to use 16-bit. Haven't used ColorPort much
but I don't think that's possible. You can doctor up the file in Photoshop -- doable, but PS
has no 16-bit input capability so you have to know enough how to calculate it.
Doing a 85-step wedge is all RGB=3 steps so that may be possible.
Bottom line: you are stepping into a quagmire trying to do this.
The second issue you are running into is changing file formats between CMYK, RGB & Gray.
Skip CMYK altogether I can't think of any use that you would likely need.
But with RGB & Gray if you convert these in Photoshop that ALWAYS involves a color management
conversion. Simple Mode change is a conversion to the new working space set in Color Settings.
Using the Ink Info palette in Photoshop also is a color management conversion for anything
that is not the actual Mode. I.e. looking at RGB for a Gray file is conversion to RGB working space.
Looking at L-values is always based on embedded profile (working one if untagged).
As Ernst mentioned Adobe RGB & GrayGamma2.2 are compatible so that is a workaround.
If you don't pay specific attention to all this you can easily end up with wrong info.
Finally given that you are on a Mac with all this, Print-Tool is really the only way to
do custom targets for curves or ICC profiles and then for actual printing. PS is wonderful
for editing images but for printing it will throw extra conversions into the mess.
Roy
On Tue, Feb 3, 2015 at 5:38 AM, richard@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
I just looked at the target I created with the numbers in my previous post. I brought it into photoshop, assigned sRGB, and then converted to GG2.2. Both the RGB and K are as expected. I just uploaded the target and the reference file to my BW shared dropbox folder.Here is the link: