D
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Re: Focoltone Question
Kyle,
Not only does the light diffusion cause the region around the dot to have a lower reflectance, it also results in the dot having light come up through it from the substrate. This would make the dot look lighter than a solid even if it had the same ink film thickness. FM screens in particular would show an increase in gamut in the vertical (L) direction due to the combined thinner ink film of the dot and due to more of the diffused light coming up through the thinner dot.
As I have been told, if one had layers of different ink or a mixture of the same proportions, the reflectance would be the same. Not sure if this is totally correct but that is what I have been told.
There is also the condition that the light reflected comes from different locations. Some goes through the ink and is reflected off the paper surface. Some goes into the paper and is diffused and then comes out in slightly different locations. Of course the ink is filtering parts of the spectrum of this light as it travels through the ink films.
But light is also reflected off particles internally in the ink film and that light never reaches the paper. You were commenting on mixing all four process inks. If you mixed C,M and Y, the too simple theory suggests that you should get black but as most printers know, you only get some kind of muddy dark colour. Also even if the ink film (CMY mix) would be very thick that does not result in black. This is due to light reflecting of the individual particles of pigments in the inks. So a normal ink film of black ink would be darker than the very thick film of CMY mixture because the black ink absorbs more of the total light while the pigments in the CMY mix still reflect parts of the spectrum.
Some light is reflected off the ink surface. Dryback is related to the difference in light reflected off the ink surface when the ink is wet and more glossy and when the ink is dry and has a slightly rougher surface.
There are lots of interesting and complicated phenomena involved and it's a bit easier to imagine what happens on coated paper but uncoated makes it even more complicated.
I used to think that modeling reflectance was useful and understanding the details of optical dot gain etc. was important but now it is much simpler in my mind. Dot gain is something for only process control at the press but not for colour management. In my view there is no place in the future for dot gain or TVI data in colour management.
So interesting but in the long run it could be better to have methods developed that don't need much thinking. Just the do the right steps with the right technology that ensures predictability, if that is possible. Always fun to think about.
Kyle,
Not only does the light diffusion cause the region around the dot to have a lower reflectance, it also results in the dot having light come up through it from the substrate. This would make the dot look lighter than a solid even if it had the same ink film thickness. FM screens in particular would show an increase in gamut in the vertical (L) direction due to the combined thinner ink film of the dot and due to more of the diffused light coming up through the thinner dot.
As I have been told, if one had layers of different ink or a mixture of the same proportions, the reflectance would be the same. Not sure if this is totally correct but that is what I have been told.
There is also the condition that the light reflected comes from different locations. Some goes through the ink and is reflected off the paper surface. Some goes into the paper and is diffused and then comes out in slightly different locations. Of course the ink is filtering parts of the spectrum of this light as it travels through the ink films.
But light is also reflected off particles internally in the ink film and that light never reaches the paper. You were commenting on mixing all four process inks. If you mixed C,M and Y, the too simple theory suggests that you should get black but as most printers know, you only get some kind of muddy dark colour. Also even if the ink film (CMY mix) would be very thick that does not result in black. This is due to light reflecting of the individual particles of pigments in the inks. So a normal ink film of black ink would be darker than the very thick film of CMY mixture because the black ink absorbs more of the total light while the pigments in the CMY mix still reflect parts of the spectrum.
Some light is reflected off the ink surface. Dryback is related to the difference in light reflected off the ink surface when the ink is wet and more glossy and when the ink is dry and has a slightly rougher surface.
There are lots of interesting and complicated phenomena involved and it's a bit easier to imagine what happens on coated paper but uncoated makes it even more complicated.
I used to think that modeling reflectance was useful and understanding the details of optical dot gain etc. was important but now it is much simpler in my mind. Dot gain is something for only process control at the press but not for colour management. In my view there is no place in the future for dot gain or TVI data in colour management.
So interesting but in the long run it could be better to have methods developed that don't need much thinking. Just the do the right steps with the right technology that ensures predictability, if that is possible. Always fun to think about.
