Digital Negative Curves

Ian-Barber

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Ive been spending some time experimenting with digital negatives contact printing with some very good results.
I quickly realised that it's not a one correction curve process, each type of paper and even batch of paper can have different tonal responses.

What I discovered was that although we send 100% black to the transfer film, by the time its gone through the darkroom process, we never actually wound up with 100% which is not surprising when you think about it. Even digital papers have their own characteristics.

What was needed was a method whereby we could in effect map the output from the inkjet printer to the output from the darkroom paper so I decided to work with an 11 patch step wedge for the mapping.

To help speed up the process, I decided to write a Photoshop action but this soon became awkward so I then decided to write a Javascript plugin and wrap the code behind a user interface. In theory, because this is Javascript it should work in Photoshop from around CS4 upwards.

main-interface.jpg

Processes:
I only print using the Silver Gelatin process and have no means of testing it with any other processes.

There is more information and a quick video on my website

https://www.digitalblackandwhite.co.uk/digital-negative-curves.html
 
QTR (Quad Tone Rip) uses different ICC profiles to produce negatives for specific processes, a negative for Silver Gelatin printing isn't suitable for say Platinum Palladium printing. In addition negatives are optimised in terms of the colour inks/pigments used to give the best exposures with UV light, so for Platinum Palladium that' a greenish black.

The other feature of QTR is it lays down a higher ink density than the Epson print driver which is needed to achieve the higher density range required for most alternative processes.

Ian
 
QTR (Quad Tone Rip) uses different ICC profiles to produce negatives for specific processes, a negative for Silver Gelatin printing isn't suitable for say Platinum Palladium printing. In addition negatives are optimised in terms of the colour inks/pigments used to give the best exposures with UV light, so for Platinum Palladium that' a greenish black.

Yes, I agree that other processors such as Platinum do require some form of blocking ink mask usually from the yellow which is why some tweaking of the script I made would need to be done in order to introduce this mix.

I am not convinced that the ABW driver is not capable of producing enough density at least for the silver gelatine process and the tests I have done have been very pleasing when setting the default tone option to darkest in the driver.
 
Presumably you could use the Cool/Warm/Sepia adjustment facility to control additional masking colours.
 
I would be careful introducing yellow because it's the most unstable of the K3 inkset. It would seem reasonable to think that the negative density could change over time. I don't know that we need to worry about keeping digital negatives for the long term, but I don't know how fast it might change...
 
Epson seem to make claims of up to seventy years for prints made with their inks. Presumably a digital negative would be stored carefully in the dark and might last even longer. This seems long enough for most purposes, but I may be misinterpreting things. I didn't find data for the specific longevity of ink on film.
 
As a matter of interest Ian, how many hours work did you put in to make this, IMHO a very useful program (script) to have.
 
I have been told by Ian over 100 hours work put into the whole project, all I can say is well well done that man and hope you can sell a few to help with the time involved.
 
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