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#27: Measuring TVI on Inkjet proofs is Meaningless

by JimRaffel on March 9, 2006

Part 5: I should start by saying I have covered the topic of using graphic arts densitometry to evaluate inkjet proofs once before. Back in July ’05 GN#5 addressed this same issue so you may wish to refer back to it. I considered changing this topic, because the title is a bit inflammatory. Understand that my frame of reference is users of our software who rely upon density and TVI as process control measurements for inkjet proof production.

Far too many times I have seen the density and TVI values stay within tolerance, and yet the Delta E shifts can be huge. Those of you who follow the blogging I do at JimRaffel.com (yes, I write more than once a week sometimes), saw a graph of the spectral response of the Red, Green, Blue, and Visual filters used in graphic arts densitometry. Those filter responses are specifically designed to address the spectral response of process cyan, magenta, yellow and black. While I was not able to find them for this week, I have seen graphs which compare the spectral response of offset printing inks with typical inkjet inks. By next week I will either find the curves or reproduce them myself once I am back in the office. A picture will be worth a thousand words when I post those graphs at JimRaffel.com.

Coming next… How important is Gloss?

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#26: Density is king

by JimRaffel on February 28, 2006

Part 4: TVI is not measured it is calculated from density which is king. All the other values our modern densitometers display are simply calculated values from the densities the instrument measures. In short, all a densitometer does is transmit a predetermined amount of light and then measure how much comes back to the instrument. This is done through Red, Green and Blue filters so the instrument can tell if the light was stopped by Cyan, Magenta, or Yellow ink.

One reader made a comment at JimRaffel.com that density is also a good indicator of ink film thickness on a printing press. Just remember that two inks with different pigment loads can record the same density and have different ink film thickness.

Coming next…Part 5 Measuring TVI of Inkjet proofs in meaningless

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#25 TVI Notebook (part 3 of 5) TVI is not a bad thing

February 21, 2006

Part 3: TVI in and of itself is not a bad thing: Back when TVI was called Dot Gain, I remember going into print shops and having pressman tell me “No, we don’t have any dot gain.” This was not ignorance (they knew they did), but instead a misconceived notion that TVI was a bad [...]

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TVI Notebook (part 2 of 5) GRACoL & TVI

February 14, 2006

Part 2: GRACoL 7 appears to be taking our pressrooms in a direction where TVI will be significantly less importance in monitoring production run stability. Instead GRACoL 7 is based on maintaining gray balance utilizing density and L*a*b* values. Over all, I feel this is the right direction to go and from what I have [...]

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#23: TVI is a better term than Dot Gain

February 7, 2006

This is Part 1 of a 5 part series from Jim Raffel’s TVI notebook. Part 1: Tone Value Increase (TVI) really is a better term than Dot Gain: My short answer for this is that a densitometer (or spectrophotometer acting as a densitometer) does not actually measure dots, so how can we really call it [...]

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Golden Nugget #5 Density & TVI or L*a*b?

July 13, 2005

This post now appears as Color Conversations: Density & TVI or L*a*b? on Color Conversations the blog of ColorMetrix Technologies, LLC. *** Introduction *** Next, I want to let you all know that since the inception of the golden nuggets idea both of the Mikes at ColorMetrix (Michael Litscher-CTO & Co-founder; Michael Woods-Technical Services Manager) [...]

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