QTR-Quadtone RIP

Hi David,

Yes, 21 pairs (including 0;0 and 100;100). The components of each pair are separated by a semi-colon. The order is always input;output. Each pair is separated from the next by a space. Here is an example:

"0;0 5;10.38 10;15.32 15;19.89 20;23.74 25;27.57 30;31.42 35;35.32 40;39.34 45;43.53 50;47.60 55;51.70 60;55.95 65;60.01 70;63.37 75;66.63 80;69.79 85;73.19 90;77.14 95;82.75 100;100"

Yes, there are decimal places. Yes, they matter. In my spreadsheet, the formula that collects them into a string actually has many more decimal places than are necessary, but since it apparently sees it as text rather than numbers there is nothing I've been able to figure out to shorten the length.

I see you are using a scanner to make your readings. Set one of the eyedroppers in the Ps Info panel to read 8-bit Grayscale and you will then get 0-100 Ink % which is what QTR needs. You probably know to adjust levels so that step 1 is white and step21 is black. You can also create a simulation of your correction curve as an actual Ps curve though you are limited to 15 or 16 points rather than 21. You can choose whether to vary input or output. Do you use a spreadsheet to calculate your curve? Mine calculates the curve varying input and keeping output constant. I can enter Density reading which are converted to percent, or ignore the density column and enter percent directly. I'll be happy to share it with you, but in all honesty Richard's spreadsheet (link in a previous message) which converts Density to Luminosity (LAB) does a much better job of actually achieving visual linearity. Using density will get you mathematically linearity but that will be visually too dark, at least to my eyes. Both my spreadsheet and Richard's provide the Gray Curve string which you simply copy & paste into the QTR profile. The problem for you as far as using Richard's spreadsheet is that it requires Density readings.

I heard that the QTR site is down because of a migration by the site host and that Roy is out of the country and not able to do anything about it until next week. 

If you go to the Files section of this group on the web, you will find most, if not all, of the documentation that is available on the QTR website. QTR Workflow by Amadou Diallo is particularly helpful and well written, though it is not about digital negatives. 

Here are a few of sites with useful information specifically about using QTR for digital negatives:
http://www.ronreeder.com/qtr-digital-negatives-and-downloads.html
http://www.clayharmon.net/words/downloads
https://jkschreiber.wordpress.com/platinumpalladium-notes/digital-negatives-with-quadtonerip/

I know my article needs some updating, but it covers the basics pretty well. Clay's download page has a lot of useful stuff including a very good article on using QTR for making Diginegs and a script for creating curves. Since you are using a scanner, this might be a good way to go. And Ron literally wrote the book on the subject. 

Cheers,
Keith

Keith Schreiber
jkschreiber.com




> On Nov 21, 2016, at 7:21 PM, David Aimone daimone@... [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com> wrote:
> 
> Keith,
> 
> 
> Ok, so if I have the concept correct, there will be 21 pairs separated by a semi-colong, one pair for each step.  I’m usually reading numbers from 0-256.  For these, am I reading input and output grayscale percentages 0-100?  Are they in pairs in the order input;output?  The output is read from scanning the print of the 21 step chart; and I assume I use the standard percentages of a 21 step chart for the input value?
> 
> I actually tried to find this information on the quadtonerip site but I think the site is down, it’s not loading in Safari or Chrome.  Yes, I’m on a Mac too.
> 
> David Aimone
> david@aimonephoto.com <mailto:david@...>
> 
> http://www.aimonephoto.com <http://www.aimonephoto.com/>
> 
> 
>> On Nov 21, 2016, at 8:36 PM, Keith Schreiber keith@... <mailto:keith@...> [QuadtoneRIP] <QuadtoneRIP@yahoogroups.com <mailto:QuadtoneRIP@yahoogroups.com>> wrote:
>> 
>> Hi David,
>> 
>> 
>> Aha! That was not clear. Or maybe I just missed it.
>> 
>> In the profile that I posted, or better yet in the text file that you made with it, find the following line:
>> 
>> GRAY_CURVE="0;0 100;100"
>> 
>> You are going to replace the part within the quotation marks with your curve. Just be sure to use the same syntax. It begins and ends with quotes. The number pairs are input;output separated by a space. It's a semi-colon NOT a colon. This is important. Then change the CURVE_NAME to reflect that this is a new curve, and save the file using the curve name as the file name. Run the install command to install the new curve, print another 21-step using it, print the new neg in the darkroom, read the steps to verify your linearization. 
>> 
>> This is all assuming you are on a Mac. It's a little different for PC users using the Curve Creator tool, but not much.
>> 
>> Cheers,
>> Keith
>> 
>> Keith Schreiber
>> jkschreiber.com <http://jkschreiber.com/>
>> 
> 
> 
>