You don’t have to spend that long in playing with colour management before the word deltaE comes up, it is after all a very complex subject with words that you will have never even heard of cropping up in paragraph after paragraph of text you read on the subject. But ever wondered what those deltaE numbers really mean?
Well quite simply put it is a single number that represents the ‘distance’ between two colours. Simple right? Well no not really since it doesn’t really help you visualise what that will mean to your job, on top of that deltaE comes in a number of flavours….. go figure! Each one has its own way of calculating that difference.
So let’s take a quick peek at what this colour difference will actually mean in the real world. I must stress this is only a simulation based on dE76 and was created some time back when I needed to simulate this subject to someone…. I’m sure one of you complete diehard colour experts out there will correct me if this is to far wrong…..
So, looking at this image the top left and right colours represent a deltaE difference of 5, you can see that I split each section into the original colour and the deltaE difference, naturally the image here in the blog is a little small to see, so you can grab a full size one on ScribD here.
Right, you can see that a dE of 5 provides a pretty big shift in colour, and this is a tolerance level of the ISO specifications, the reality is that the measurement systems out there measure only a selection of swatches and provide you with a max, min and average reading for the swatches that are read, far better than anything we had years ago and given the number of variables involved in laying down ink on paper it’s a miracle that we can reproduce images on multiple different mediums that come out looking roughly the same….
Hold on…. did I say multiple mediums, yes, let’s think about this for a second and the changing trend moving back to running by numbers, just those numbers are now ISO target values rather than ink density weights…. When a hard copy proof is produced, the proof is measured to provide a tolerance rating to the given specification it has been produced to, in modern proofing situations it can be expected to get the dE down to well below 3 depending on the hardware/ink/paper combinations, in soft proofing, these tolerances can be even closer given the control available in the modern monitors, then on press you work within the same tolerances.
But running to numbers or running to match the contract proof? Both should yield a pretty accurate rendition of your subject matter, but what is the customer, brand owner expecting? Given that the different mediums could all shift in different directions making the actual difference between say hard copy proof and final print a dE outside of what the acceptable tolerance is, yet individually they would be in tolerance.
We’re a long way forward in the world of colour matching, and the ability to communicate what realistically can be expected when you get to press and the ability to measure what is coming off of press with far more accuracy than ever before should mean that the consistency of good quality colour matching print will continue in the future.
Oh yes and as pointed out by Adam Dewitz of PrintCEO.com (thanks Adam, I should have included it first time around) if you want the full technical detail, the pure hardcore send yourself to sleep kinda stuff, then head over to http://printwiki.org/Delta_E they have a pretty good explaination of how it really works along with a biot og history on it.
Author: Gary George
This work is licensed under a Creative Commons Attribution-Noncommercial 2.0 UK: England & Wales License.