Quad Tone RIP

Helen B

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"Just invert the image file to make a negative, and let the ink settings in your QTR profile adjust negative contrast and linearize the midtones."

Why not just make an inverted profile? It works with IJC/OPM, so I assume that it would work with QTR.

Best,
Helen
 

Ron-san

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Helen--I am not familiar with IJC/OPM, but the way I do it in QTR is to start with a grayscale step tablet on the computer screen. Then I invert it to a neg, print the neg using QTR and a "best guess" QTR profile, then print the neg on a piece of palladium coated paper to make a positive print and use a flat bed scanner to measure what tones actually came out in the positive print. Then the Input/Output values (step tones in the computer/tones measured on the final print) are each subtracted from 100 to transpose them from positive space to negative space, then the transposed pairs are inverted and fed into the gray curve function of the "best guess" QTR profile to effect the final linearization.
If the correction curve is destined to be applied as a Photoshop curve to the original positive image in the computer, then a simple inversion of the number pairs is all you need. But if the correction is to be applied to the negative itself (via the QTR ink settings) you need to do the transposition to negative space as well.
Does this answer your question?
 

clay

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Welcome aboard Ron. I have your book already pre-ordered from Amazon. Is the link working yet with your update?

I appreciate the feedback. It sounds like you have already covered a lot of this ground already. I agree with you that colorization per se is irrelevant. What matters is getting the mapping of the tones correct on the negative. I think one of the original selling points behind colorized negatives was that you used the least amount of ink to do the job, which by implication meant that people had the premise that too much ink is bad. I don't necessarily drink that Kool Aid. I know that the PDN system goes to great lengths to avoid the use of black ink. The quick and dirty approach I developed uses black ink since everything is in RGB space, and frankly, I see no problems with it.

Anyway, it sounds like you may have already developed what we have been thinking about here. Is there any chance you can make some of your QTR profiles for the common Epson printers available here on the site? Or do you have a companion CD or something with your book? In any case, it is interesting to hear that you have developed this approach, and I am very keen to try it out.

Again, welcome.
 

Ron-san

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Clay-- As you can tell, I have jumped the gun a bit. The book will not be out until December 1 and our website with its updates, is still under construction. I hope by December 1 all will be in place. All best, Ron
 

Helen B

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Ron-san said:
Helen--I am not familiar with IJC/OPM, but the way I do it in QTR is to start with a grayscale step tablet on the computer screen. Then I invert it to a neg,...
Does this answer your question?
Click to expand...

Thanks for the reply. I didn't explain myself very well.

I don't invert the positive image in Photoshop, the profile takes care of that - ie it lays down more ink for a PS value of 255 than it does for 0, instead of the normal way of laying down the most ink for 0 and no ink for 255. No adjustment curve or inversion is applied in PS - you just get the positive image looking as you want it, then print it using the 'IG2.1K' profile, for example.

Best,
Helen
 
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mkochsch

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I think a "negative" option would have to be a feature added into QTR. Basically inverting the bit values. Relatively simple (one hopes). I think QTR is always assuming it's printing a positive. Why don't you send a note requesting the feature to Roy at quadtone@harrington.com and see if he's willing to add it?
 

Helen B

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Well, as I use IJC/OPM instead of QTR I'm not really the best person to ask Roy for something. I'd be very happy to help in the development of QTR for digital negatives. I also wonder how much interest there would be in a dedicated ink set for digital negatives for use with QTR or IJC/OPM, rather like the Cone K7 set but optimised for transmissive use on OHP film.

Best,
Helen
 
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Ron-san

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M--
QTR has at least three different methods for linearising midtones. One is to use the Gray Highlight, Gray Shadow and Gray Gamma settings to get an approximate linearization. Another is the Linearize function I think you are talking about which takes densitometer readings of the output and attempts to linearize from that. The method I am using is a function called "Gray Curve" which, in the profiles where I have seen it used, is located just below Gray highlight, shadow, and gamma. Gray Curve takes Input/Output values (expressed in % black), suitably transposed into negative space and inverted and uses them to attempt a linearization. Usually it is a good idea to get in the ball park with Gray highlight, shadow and gamma before using the Gray Curve function.
In any event, the two .txt files I attached to my post are complete QTR profiles. To use them they just need to be installed using the Install script.
Does this help? Cheers, Ron Reeder
 

mkochsch

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Install Script? I don't see anything about an install script in the literature (FWIW I'm using W2K). Are the txt files you attached QIDF or PPD files or something else? What I was seeing looked like it was imported incorrectly. Like the wrong data showed up in the wrong cell.
 

Ron-san

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M--
What we have here is a Mac versus PC problem. It is my understanding that QTR provides the same functionality for both computer platforms, but the interface for the Mac is quite different than the user interface for the PC. I am a Mac guy, and was giving you Mac instructions. You are clearly a PC user and no wonder my instructions were confusing.
Here is how I understand you go about installing a new QTR profile on the PC -- but bear in mind I am not a native PC speaker and you may have to help me parse the instructions. The Mac and PC versions of QTR profiles are identical text files, but the PC files are identified as qidf files. On the PC a new profile need only be moved to an appropriate folder to install it (you do not use an Install Script like on the Mac). I believe the appropriate folder is located at C:\Program Files\QuadToneRIP\Profiles Drag the new profile into this folder, and I hope it works.
Let me know if you are able/unable to install either of the QTR profiles I supplied in the earlier post.

Ron Reeder
 

Ron-san

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clay said:
Is there any chance you can make some of your QTR profiles for the common Epson printers available here on the site?

Again, welcome.
Click to expand...

Clay-- Don't know what I was thinking when you made this request. There is no reason to wait until we get the kinks ironed out of our website. Here are the two QTR profiles I have written for making digital negatives with the 2200. One is for palladium printing and the other is for silver printing. I also post the ReadMe file that tells the specific conditions the profiles were contstructed for.

Let me know how these work out. Ron Reeder
 

clay

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Wow. Thanks! I will give them a shot this afternoon.

While the thought of not spending hours in front of a computer screen trying to reinvent the wheel is a little sad, I think I will just have to adjust to the idea and go make some prints.

This is quite generous.

 

Ron-san

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clay said:
I will give them a shot this afternoon.
Click to expand...

Clay-- Be advised that these two profiles were written when I was still using dark black and light black inks to print negatives. I now know that using all seven inks gives much smoother tones. However, I have not yet had time to write seven ink profiles for the 2200. These will get you started and give you a flavor of what the QTR approach can do. If you like I maybe I can later show you how to write them for all seven inks. Cheers, Ron Reeder
 

Kerik

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Ron,

Glad to see you here. What a coincidence - I just saw one of your pt/pd prints at the Viewpoint Auction in Sacramento yesterday. Beautiful work! I'm looking forward to purchasing your digineg book when it hits the streets.
 

mkochsch

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Thanks Ron,
I think what I'm seeing is QTR's ability to do something more than one way. It looks like it can either take an ACV or RAW file in the file open dialogue in Grey Curve. Or, one can enter the numbers in directly if surrounded by quotes.
 

mkochsch

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When you say seven inks do you mean seven grey inks or seven CMYK inks?
 

Ron-san

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mkochsch said:
When you say seven inks do you mean seven grey inks or seven CMYK inks?
Click to expand...

M-- As you may be able to tell, I only know enough about QTR to make one set of actions work. I definitely do not know all the bells and whistles that are available in it. When I use Gray Curve to finalize tonal linearization I use paired numbers typed in between quotes. I believe you are right that gray curve can use a .acv curve. But, as I tried to explain in an earlier post to Helen Bach, to work for printing negatives the number pairs must first be transposed from positive space to negative space and then inverted. That is what I have done for the number pairs in all the QTR profiles I have posted here.
When I say seven inks, I am talking about the seven Ultrachrome inks used by my Epson 4000 (and by the 2200 as well) Matte Black, Light Black, Cyan, Light Cyan, Magenta, Light Magenta, and Yellow.

Ron Reeder
 

Helen B

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Ron-san said:
... But, as I tried to explain in an earlier post to Helen Bach, to work for printing negatives the number pairs must first be transposed from positive space to negative space and then inverted. ...
Click to expand...

Ron,

My original question was about why there was a necessity to do inversions and apply adjustment curves in Photoshop - which I asked because I had assumed that QTR had similar functional capabilities to IJC/OPM (apart from the ability to linearise directly from an Eye-One). Having read the remarks here, and having now tried QTR, I can see that it is a more convoluted route. The method I use is very simple and intuitive in IJC - I never considered doing it any other way, and I was puzzled about why QTR was being used differently.

Is there enough interest to approach Roy Harrington to get a negative option added? The alternative would be to write a separate little program to make the curves and linearise them. As far as I can see there is nothing in the current version of QTR to prevent the use of negative profiles, except for the way in which they would have to be made. Have I missed something?

Best,
Helen
 

Greg_E

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Helen, it really doesn't need to be in QTR itself, but just a function inside the GUI to flip things into negative. Once again I'll say that after looking at both applications, the GUI for IJC/OPM really makes it easy to use, and probably well worth the increase in price. It should be noted that to really get the most out of these applications, that you will need a densitometer to measure the different targets used in linearizing the the output. Better is to use a supported spectrophotometer, but that gets into even more money.
 

Ron-san

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Helen Bach said:
Ron,

My original question was about why there was a necessity to do inversions and apply adjustment curves in Photoshop.
Helen
Click to expand...

Helen-- You can either put the correction curve on the positive image file, as a Photoshop curve, or you apply the corrections to the negative, down in the ink settings, which is the approach I use with QTR. I think there are advantages to doing it in the ink settings which make up for being a somewhat less user friendly approach.

Ron Reeder
 

Ron-san

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Greg-- There is always more than one way to skin the cat and if IJC/OPM gives you tools to write profiles for the ink settings, then I am sure it can do the same thing QTR can do. QTR only costs $50 and the method I use employs nearly any flat bed scanner -- it does not use a densitometer. But any printer driver that allows you to write ink profiles should be able to do the trick.
Ron Reeder
 

Helen B

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Greg_E said:
Helen, it really doesn't need to be in QTR itself, but just a function inside the GUI to flip things into negative...
Click to expand...

I'm probably not explaining myself very well here. The method I use does not involve flipping anything into the negative in any part of the user interface, it is an inherently negative process in that it puts down no ink when sent a pixel value of 1 and full ink when sent a pixel value of 255. QTR appears to be able to do that already, it is just the curve creation and linearisation methods that make it a little awkward (but not impossible).

Best,
Helen
 

Kees

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Hi Helen,
You are explaining youself very well. Your idea of inverting in the driver directly whithout checking options before printing is possible wih QTR. This means that in the inkdescriptor file the pos-neg change should be made by 'inverting' the grey curve. Then, you can print from a positive file and get a negative print directly just by choosing the right QTR-curve. I suggested this workflow allready in 2003 on the altphoto list when I talked about agfa copyjet and QTR. See the second part of this post:

Dead Link Removed

But .. actually I never used this method because inverting in photoshop is so easy and you also have to do a 'flip horizontal' step because the printing side is downwards when printing.

But I do put my process correction curves in the inkdescriptor file. By the way, it is not neccesary to put percentage pairs in the inkdescriptor file. You can also put the name of the photoshop .acv correction curve file that has to reside in the same folder as the inkdescriptor file.

Is is a nice idea though to prepair all your process curves, printing color, even inverting and pack everyting in process related QTR-curves. Then when you choose QTR-platinum, QTR-Cyano or QTR-gum etc. you get the right negative in one step while still seeing your gorgeous positive on screen. Only the 'emulsion down' flipping can't be done this way I think.

kees
 
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Kees

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QTR, how many workflows?

Hi,

We talked about using QTR for digital negatives and I noticed that there are four (or maybe more) different approaches. I am trying to list them here:

1. QTR BW workflow with quad black inks

This is what QTR was made for. You have to use a dedicated printer with black and grey inks or one of the newer K3 printers. Third party inksets are sold by MIS or Cone and others.

Each grey ink overlaps the previous and this can be controlled in the inkdescriptor file. A no K, only grey, approach is also possible. Process related density range can be controlled by setting ink limits. Process related correction/linearization curves can be specified in the gray_curve setting or applied in photoshop. (Note: does QTR handle these curves in 16 bit? If not, it is probably better to keep using them in photoshop on 16bit files)

2. QTR BW workflow with K and LK in a printer with color inks.

As I understand Ron correctly, and after looking at his 2200 Pd and silver sample files, in his workflow only K and LK are used in combination with ink limit settings for density range control. All other inks are not used by specifying them as 'unused' or setting inklimits to zero. As an only grey approach it is not very different from the first approach but it uses only two inks.

3. QTR BW workflow with all (color) inks.

This workflow uses all inks with or without K an LK to print a BW negative with all inks. Default ink limit settings control negative densitity range.
Ron's earlier example files are using copy_curve to copy and set values for each color. But individual values for each ink after measuring the inkseparation print can be set in the descriptor file also.


4. QTR colorized negatives

This is a different approach and maybe combines the best of two worlds. Here the process related density range is achieved by spectral density and finetuned by ink limit settings. For each CMY color and/or two color combinations CM, CY, MY a monochrome QTR profile is made. All other inks are set to unused. CY gives a high contrast range suitable for long scale processes like salt or albumen printing. CM gives a low contrast suitable for gum printing. Contrast control and finetuning can be done by mixing two QTR-curves or by taking down inklimits (or both).

This method would work even better with a ternary CMY calibration file of some sort to choose the right color for each process.

What approach gives the best results is difficult to say. When density range has to be very long, a spectral density negative might be the way to go.

To get the smoothest negative possible probably asks for a print with as many inks as possible. Inks that behave differently (K) than others (colors, greys) can be problematic so an 'all colors, no K' BW approach might be interesting. When using K2 K3 inksets a toner color can be mixed in for density range control.

And there's allways the printing substrate that has a big influence on the density range and smoothness of the negative. Different printers and inksets of course too.

Ok, I'm back to testing!

kees
 
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