Unfortunately, there is no direct relationship with ink consumption and image area of the plate. It depends on what is being printed and errors can be quite large if one bases consumption on image coverage alone.
I am surprised you said this. What do you mean by negligible? As I stated earlier, it depends on what is being printed. If there is no overprinting, then it is not a factor. If there is a lot of overprinting, then it is a big factor.
By negligible I mean that typical production presswork the reduction in volume of ink usage caused by wet trapping is so little that it’s irrelevant.
Of course I’m speculating - you appear to be doing as well - since AFAIK there have not been any formal studies. And I’m not ready to accept the anecdotal testimony of printers. I’m surprised that you are. ;-)
One could probably model the problem in photoshop to get an idea as to the area of ink that is actually overprinted in a sampling of halftone screened images. Then use that to calculate the volume of ink represented by the areas of overprinting assuming a reduction of, perhaps, 0.3 microns of ink film thickness in the overprinted (wet trapped) areas.
Can you point to any studies that have been done along these lines?
I do hope that this forum is broad enough to host ALL the information available, held by whatever view the person holds.
A little of my background, - 6-year apprenticeship in an average UK Printing Company, not exactly at the forefront of printing
technology, but I was lucky enough to attend the area "School of Printing Technology" What would you think when some of the
Journey-men instructed me to get a Bottle of Stale Beer which they said would cure the problem or they would delve into
their waistcoat pocket take out a pinch of some powder and add it to the Ink! - enough of me reminiscing!
So Erik onto the next item - a dreaded PDF - but from one of my early Text Books, do read the Preface by Dr V.G.W. Harrison PATRA