QTR-Quadtone RIP

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> I have a few B&W alt process photographers in my area and some who have asked about whether the glossy carbon inkset I've been using lately would be suitable for alt process internegatives.   So, I've tip-toed into the arcane realm of alt process to see if I can help my friends simplify and maybe rationalize their (rather SOP now) workflows.  Time will tell.  I do not anticipate participating in wet darkroom work myself.

It’s important to have a darkroom for this in order to anticipate users needs, adapt the system to that, and support them properly.

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> These are some very preliminary thoughts that need to be taken as such. 
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> My first conclusion is that the glossy carbon inks I use will work just fine.  However, OEM k3 inks also are just fine.


This depends upon density of black. For develop-out methods that have expensive NA2 or Platinum as a restrainer, it generally works ok but for print-out you often need more density for that or a very specifically tuned K. I suggest carbon-based gloss inks if you want a system that is more adaptable to various ferric print methods including MaldeWare, Ziatype, salt, etc.

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> The local alt process photographer/gallery owner uses a 3880 with OEM inks.  So, that is mostly what I'm looking at.  However, my experiments with my carbon inks and the 3880 OEM inks suggest that the same concepts will apply to both, with the obvious roll of the yellow ink missing in the carbon ink situation. 
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> The alt process we're now focusing on is based on the Bostick & Sullivan platinum emulsion chemistry.  Exposure is via a metal halide broad spectrum light.  This measures its own light.  So, one just dials in a number  and the light does the rest.  Currently the basic exposure (dmax reached through the film base) has been set at 24, but as the scan fo the final print (link below) shows, it's not quite on the mark yet.  The exposure outside the film base is slightly darker.

Are you using 24 “units” of light? All of this is vastly different from one user to another depending upon light source (spectral range and watts and lux). It’s not a useful number unless someone has the same or nearly the same exposing unit. What one are you using and what is the bulb’s model type and #?

This proper exposure can be calculated with a stouffer strip. The formula is found directly on the stouffer strip’s envelope.

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> That said, the scan of a QTR Calibration Mode print on Inkpress film and then contact printed on the platinum print paper is close enough to see what is going on.  Below the scanned image I have the Excel graphs of the PK, LK, LLK and Y inks.  The graphs are up to "50%" on the Calibration Mode print, but have as the starting point the paper outside the film base.  
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> http://www.paulroark.com/BW-Info/QTR-Calibration-Mode-Platinum-3880-24.pdf <http://www.paulroark.com/BW-Info/QTR-Calibration-Mode-Platinum-3880-24.pdf>

This PDF does not show paper white vs patch white so there is no real way to judge light fog. Ideally the shade 2 channel alone should have the strength to eliminate exposure entirely and the rest of the channels in the HLs simply take out the noise while K bumps it past its fog point even more.

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> From what I've seen so far, I am going to recommend the M and C colors be ignored and not used.  Frankly, the hand coated paper is so rough that the fine details we worry about in inkjet printing on coated papers are of little concern.  No dots or microbanding are ever going to show (and the 3880 with OEM inks is so smooth they don't show in normal printing either).  At least for the platinum printing like this, we don't need many inks.  


But issues do show. I’ve certainly seen micro lines myself when making K3 curves and also even with K6 inks on older printers. It’s just a matter of whether you are using a vacuum frame and a single point light source (something very very many people who have invested in Pt/Pd metals have). Proper overlapping of curves in this situation is important. Generally speaking, PtPd printing is a significant investment. People want the best negs possible for it. One thing that often shows before even lines when improper neg-making methods and materials are applied is blotches in mid-tone sky gradients and the “venetian blind” effect seen as vertical banding from miss-aligned heads that only shows in-darkroom when not using enough ink and wrong media/platen settings.


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> The yellow has essentially the same UV density as the PK.  (I do not know exactly what the B&S chemistry spectral sensitivity is.  So, this may vary with the emulsion type and mix.)

Mike Ware and several others have written extensively about the spectral range, check it out online. "An Investigation of. Platinum and Palladium Printing" <http://www.mikeware.co.uk/downloads/Palladium_Printing.doc>
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> With the Yellow in effect the same as the PK, I will probably do a "copy curve" from the PK and cut the ink limits in half.  The boost, however, only affects the K.  So, whatever boost is settled on will apply only to the PK.
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> (An alternative approach that I like for normal printing and might take here is to use the yellow as a separate toner channel, with density 100 so that it becomes a "black only" type of curve.  This can then be taken manual and be a way to get the pre-linearization curve essentially perfect.  But this is a bit further down the road.)
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> My early profiling on Pictorico White Film ("PWF"), then printed on Inkpress film and scanned with a Nikon 8000 to see what the transmission densities looked like, suggested a potentially interesting approach to transparency profiling.  The PWF profiles used to print on the film produced films that looked way too light.  Of course, with a reflective print the light goes through the inkjet coating twice -- once to reach the paper, then the reflection back to our eyes.  So, the transparency is about half the density of the reflective media in the midtones.  Then near the 100% black end it dives in a very non-linear fashion to the black point.  

film profiling has always been the traditional way. whatever floats one’s boat. It’s not as accurate but makes a decent “classic” negative if you dial the densities into the right curve. The problems lie in the highlights if you are going this route.

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> What largely offsets the printing differences is to simply alter the PWF profile gray gamma from the default 1 to gamma  0.4 for the transparency.  To offset an un-wanted flattening of the K curve at the end, there should be a boost of at least 10 for the K.  That is, if the ultimate K ink limit was 50, set the K limit to 40 and boost to 50.  Then the transparency became quite linear even before linearization, (which I am currently thinking should not be done at all at the internegative stage).

It’s not about having the transparency densities be linear per-say, but again, whatever floats one’s boat.

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> There are so many variables in the alt process workflows, that very simplified QTR profiling would seem to be a benefit for that group.  Whether my outsider's look is useful remains to be seen.  Those that wander into the alt process realm have my admiration and sympathy.


The main control factor in profiling for alt-process is controlling darkroom procedures and then profiling properly from the printed densities while controlling for light falloff and coating inconsistencies that always happen. Separating what can be improved by hand and what must be corrected for algorithmically after measurement and before the linearization takes place is the key. 

The normal way to profile QTR negs is by eyeball or 21step spectro (as little paper amount as possible or 21x4 to  account of coating issues), tweaking an internal set of overlaps or gray curves and then publishing a system that requires a final photoshop curve or internal QTR tuning curve to pass muster. This is ok to a point as long as the original curves and overlaps and inks all play well together, but it often lacks bit-depth and adjustability in shadows and highlights which is critical. After all, PtPd is known for its long tonal range/compression of the highlights. If the negative can’t print that subtle transition, than the qualities of the medium are disabled. You really need at least 21 steps calibrated in just the shadows and just the highlights alone to achieve good opticals.

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The one key factor in digital negatives that Piezography didn’t address with its first system 5 years ago was hardness. While our gloss ink is micro-encapsulated and way harder than any other multi-tone carbon ink on the market besides OEM, it was still not as hard as epson K3 resin-encapsulated ink and because we are printing much higher (required) amounts, this made the negative fragile and prone to scratching. We invented a way to do same-time gloss optimizer in a 7th channel to harden the negative. Inks that do not contain a significant percentage of copolymer or resin encapsulation will just not work at all and spread out too much. I suggest sticking w/ K3 ink or going Piezo to enable physically workable negatives. (our upcoming Pro inks will have an entirely different and much more robust strength when it comes to this).

I say all this because I basically figured out all the physical and mathematical and round-trip workflow variables already and made a system that prints at the same quality as silver negs for PtPd. piezodn.inkjetmall.com <http://piezodn.inkjetmall.com/> for info. Specifically check out the Download section with the roadmap and updates. We keep it continually R&D’d based on user feedback. Free updates for life. 

cheers,
Walker

ps: I don’t exactly recommend InkPress transparencies as it generally doesn’t take the ink load that is needed for dependably smooth tonal transitions. It blotches and doesn’t have stellar QC from batch to batch in my and other’s experience. The only base that I’ve seen cut it when making negs for a process that can cost upwards of 20 dollars per sheet in metal is Pictorico Ultra Premium OHP. It takes proper carbon ink loads that is.

pss: A good proof-of-viability test for anyone buying a neg system requiring an investment in third party ink and cartridges is to see if it works with silver. If it works with silver, it will work for everything else without limitation or worry.


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> Paul
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