Thank you Andrei, that was very interesting and helpful! It would be even more interesting though if maybe Gordon saw this, and shared his comments to your link!
I'm crossing my fingers for that....
The Luscher paper, as Kevin from Kodak pointed out, completely misunderstands the technology and value propositions - so their arguments against it are completely irrelevant. They also extensively quote a GATF report on FM screening which had been discredited (due to the poor methodology used in the study), and which was redone the following year in order to try and make up for the initial inadequacies.
I'm surprised and disappointed that Luscher is still using that document. At the very least they should update it with better argumentation.
Since I'm no longer employed at Kodak I'll let them argue the merits of their squarespot technology.
I will however speak to the points made in the GATF study they used, because poor research methodologies often result misinformation being propagated through the industry.
Luscher is referring to the 2003 GATF Research and Technology report "Stochastic and hybrid screening printability study" by Gregory Radencic.
• The Testing Method
Luscher says: "The test forms were sent to screen-technology suppliers with the request that they expose the test forms on a plate of their choice, without using correction curves, and send the plates to the GATF for printing."
In actuality curves were applied during the RGB to CMYK separation process (pg 6 "The conversion process [RGB to CMYK] was a custom conversion in Photoshop for the anticipated amount of midtone gain."
Were the plates imaged without using correction curves. No. (pg 7 "dot area [on plate] measured from a positive curve applying 5% to the midtone to a negative curve reducing the dot area by as much as 10%." The plate linearity was all over the place. Interestingly the Luscher plates were some of the least linear with a spread of 4% at 50% for 300 lpi and 6% at 20 micron FM. Between different screen rulings in one color from 150 lpi to 10 micron the spread was as high as 14%. (pg 34 of the research paper)
Also, GATF mixed significantly different screening on their test form (5 different screens) a big problem since the different ink/water balance requirements on the same plate would be significant. (Note, for that reason Creo did not follow GATF's request. Instead, even though the Creo workflow allowed for it, we instead supplied plates with only one screening type on each set.) Also, some plates were imaged at 2400 dpi and others at 3600 dpi and 4000 dpi adding yet more variables to the research.
• The Participants
Correctly stated
• The Results
Luscher says: "With this screening survey, GATF either consciously or unconsciously answered the question whether square laser spots are better than round laser spots." That is a ridiculous statement with no relationship to the GATF study at all.
GATF summarised their own evaluation as follows: stochastic (=FM) screens have
• a higher tone value increase (GP - obviously, smaller dots AM/XM or FM have larger perimeter to area ratios and hence more dot gain. The printer simply compensates for that with a curve applied to the plate.)
• no increase of gamut (GP - Incorrect. GATF measured gamut based on solid ink densities - i.e. they measured a 2 dimensional gamut. However, gamut is 3 dimensional and if they had measured that they would have seen the increased FM gamut.)
• a slightly different grey balance (GP This can occur but is simple to correct if it does)
• smoother gradation (GP Yes)
• elimination of moirées (GP Yes)
• better skin tones (GP Yes)
• a higher degree of colour printing (GP I think this means better quality color? If so yes.)
• Resolution/Contrast
Luscher writes: "A major advantage of FM screens is their high resolution, with which, in theory, a better reproduction of image details can be achieved in comparison to autotypical raster dots. In practice, such details only make an impact if finest image structures, such as in fabrics, prevent a moirée."
I would argue that printers are in the business of reproducing original art - the more faithful a reproduction of the original they can achieve the better they are at doing their job. As one print buyer said to me - "I don't see dots in my art and I don't want to see dots in my presswork."
Luscher writes: "On the other hand, an image printed with autotypical raster dots has a higher contrast, because the white paper between the raster dots has a contrast-increasing effect on the eye."
That is correct for low frequency AM/XM halftones such as is true for newspaper work but not true for 150 lpi AM/XM screens and finer.
• Screen Ruling/Procedure Safety
What Luscher writes is best answered by Kodak as it refers to plate imaging integrity.
• What does this mean in Practice?
What Luscher says is correct.
• 10 µm FM Screen: not advisable
What Luscher says is somewhat correct. It is true the move to a 10 µm fine FM screen, the processing latitude is so tight, as if one were to print with a 350 screen without visible improvement in the printed image when compared with a 20 µm screen. But for those printers and customers who find value in 10 micron FM, they will do what it takes to implement the technology. For example, Watkins Litho in Kansas is a printer who's business was turned completely around because they implemented 10 micron FM in order to attract work from companies such as Hallmark Greeting cards (which have been done 10 micron FM for many years)
Luscher says: "Not a single one of the advantages of stochastic screening ascertained by GATF is improved by the 10 µm FM
screen!"
For the things that GATF researched, yes. But not for the things that GATF didn't research.
Luscher says: "We therefore expressly discourage our customers from this." Interestingly Luscher was one of only 2 vendors who provided 10 micron FM plates for testing (the other was Creo)
I prefer it when vendors empower me with their solutions rather than discourage me from exploiting the value locked up in their solutions.
Luscher writes: "When summing up the pros and cons of 10µm FM screening, it seems as if this is as big a marketing ploy
as the alleged advantages of square laser spots; we can thus refute two myths on thermal screening in one go."
Again, an irrelevant statement resulting from a complete lack of understanding of Creo/Kodak technology.
studentkarin, if you've read this far, I would be very interested in your description of the value/benefits of Kodak's squarepot imaging technology, perhaps in bullet point form, based on your understanding from your research. In other words, how do you think a Kodak sales representative would describe the benefit(s) or value of the technology to the printer, perhaps in comparison to competing offers.
best, gordon pritchard
(Former marketing manager for Kodak squarespot imaging but no longer an apologist for their technology)
