Screen Printing HSB and Color Separations

[drdot]

Tony,

Underbasing is another really complex idea. And once again, the solutions out there are all over the place.  Underbasing works best with the HSB model (surprise.)  The difference between Brightness and Value is Brightness is based on emissivity and Value is based on reflectance.  Think of emissivity as how much light is being emitted. So for a computer pixel 100% birghtness means 100% power to the pixel. So we want to put 100% color behind 100% brightness color values. If you want to see the radical differnce between Brightness and Value calculations use the color picker in Photoshop and compare hs B value with L ab  for a color like 185 Red.  That is the simple answer, but it gets more complex, naturally that rabbit hole again

When you have a wet white under or over a color, you are desaturating toward white. In order to maintain saturation, you need variying degrees of dry white and wet with. So the transform is really two dimensional. The first dimension is to preserve the brightness and the second to preserve saturation. So two colors with 100% brightness will have dry white under the 100% saturation and wet whites behind the high brightness but decreasinging saturation colors. Again, this benefits from having the ability to create selective underbasing by color in the separation.

As a guide in picking colors for your separtion. My experience has been the best gamut results come when the B value is greater than 60%.

This type of underbase can be created in Photoshop if you use the HSB filter. It is getting harder and harder to find and to my knowledge is not available for 16 bit color calculation. That means it is only available for CS5 and lower. If anyone knows differently, I would really like to know about it.

[inkman996]

  Man you guys make my head hurt!

I have a solution throw some 4cp color inks in the screen and call it a day! Seriously just kidding of course.

[IntegrityShirts]

Tony,

Underbasing is another really complex idea. And once again, the solutions out there are all over the place.  Underbasing works best with the HSB model (surprise.)  The difference between Brightness and Value is Brightness is based on emissivity and Value is based on reflectance.  Think of emissivity as how much light is being emitted. So for a computer pixel 100% birghtness means 100% power to the pixel. So we want to put 100% color behind 100% brightness color values. If you want to see the radical differnce between Brightness and Value calculations use the color picker in Photoshop and compare hs B value with L ab  for a color like 185 Red.  That is the simple answer, but it gets more complex, naturally that rabbit hole again

When you have a wet white under or over a color, you are desaturating toward white. In order to maintain saturation, you need variying degrees of dry white and wet with. So the transform is really two dimensional. The first dimension is to preserve the brightness and the second to preserve saturation. So two colors with 100% brightness will have dry white under the 100% saturation and wet whites behind the high brightness but decreasinging saturation colors. Again, this benefits from having the ability to create selective underbasing by color in the separation.

As a guide in picking colors for your separtion. My experience has been the best gamut results come when the B value is greater than 60%.

This type of underbase can be created in Photoshop if you use the HSB filter. It is getting harder and harder to find and to my knowledge is not available for 16 bit color calculation. That means it is only available for CS5 and lower. If anyone knows differently, I would really like to know about it.

Here's a link to the optional plug-ins for CS5 32 and 64 bit versions:
http://www.adobe.com/support/downloads/detail.jsp?ftpID=4688

The HSB filter is inside the Optional MultiPlugin.8BF

That said, I have no idea how to use it!! How would you use it to create a great underbase?

[AdvancedArtist]

I am lovin this thread now...  But I would like to try and see if we can keep it simple for those that do not get all the scientific stuff. Which is a tall order I know. Maybe I will start another thread so we can try to break this down into simpler terms.

[tonypep]

Tis is the best example of a percentage tone UB in PS that I had laying around. Most apparent in the shirt and hair but you get the idea. And yes there is blue in the hair. The UB was discharge

[AdvancedArtist]

Great looking print.. One of things I have noticed over the last year of looking at things in HSB is that color does get into places you would not think it would be. Especially with the reflections from the environment the photos where taken in. We have been playing with allot of 3D stuff lately and in those environments it is really obvious what can be going on with the light.

[drdot]

With HSB, if there is color there, it will get pulled into the appropriate channel.  When all this was going down, I found myself seeking out museums and studying paintings for hours trying to develop and awareness and understanding of what was going on.  When you really look at a Monet or Rembrandt, or any of the impressionist painters work, you immediately get it.   At that time I was lucky enough to be traveling about every other week and found myself in some amazing cities with fantastic museums. The National Gallery in Washington DC, Art Institute in Chicago, Salvador Dali museum in St Petersburg, Fl.  Those were incredible times of discovery and enlightenment.  Sadly, 99% of printers never get past the basics and do not experience the satisfaction and accomplishment of faithful color reproduction. For the majority in this indusry it is all about how fast and how cheap it can be done.  Close enough is never close enough, but it is commercially acceptable.  This thread and this forum in particular are a move in the right direction.

There's nothing simple or fast about understanding and learning to "See" color.  Until you can look at a very, very pastel neutral grey and be able to see the 2% or 3% color cast or look at a shadow and "see" the complement of the color of light in the shadow,  you will never appreciate the possibilities.  I'm not being critical but I think most of you know what I'm talking about. Very few want to put in the time, effort, and yes, hard work to really perfect their craft. Digital makes it worse because everyone thinks it's instant everything.

The beauty about really high end color is that the results can be so good, you literally can't put a finger on what makes it looks so great. The underlying subetlies give the color a richness and quality that you're immediately aware of.

[AdvancedArtist]

Yeah it is so true.. I mean I look at everything with HSB eyes all the time now. I have by no means perfected it and sometimes I just sit here sepping manually 3d renders and photos and things I find online. Its seems as though the deeper you go the easier it is to understand. Not that I would consider myself a master by any means but I would have never imagined how easy it can be when you get some basic understanding. Which is the intuitive part of HSB.

[blue moon]

I will find time to respond, I will find time to respond . . . . . . buried with artwork today. Still working on the films for tomorrow. <chanting> I will find time to respond, I will find time to respond . . .

pierre

[AdvancedArtist]

I was just thinking I do not want to get to far away from my life raft the water is getting pretty deep around here. Looking forward to your post pierre

[Dottonedan]

The water is deep and warm. DIVE IN!


Wow. Great stuff. Good thread. For now, I don't have much to contribute.

[blue moon]

I was just thinking I do not want to get to far away from my life raft the water is getting pretty deep around here. Looking forward to your post pierre

you give me too much credit, I just have a million questions and very little actual knowledge to contribute. . . Mark is doing the heavy lifting here and it is just AWESOME to get this kind of information!

pierre

[AdvancedArtist]

you give me too much credit, I just have a million questions and very little actual knowledge to contribute. . . Mark is doing the heavy lifting here and it is just AWESOME to get this kind of information!

pierre

I was referring to Marks posts and wait till Jeff comes in its gonna get really deep around here. It is really cool because I taught Jeff 8 years ago now Jeff teaches me and I take that and teach. I am a teacher that is the gift that compliments my artistic gifts. Just like the colors that we are talking about. So with Jeff watching the harvest come back is just.. well there are no words for that.

[blue moon]

Actually and this my sound like it is out there... But because we are dealing with math I see us being very close to what you just outlined within a year. Not with every detail you have listed but very close. Because color values and densities in the digital space can be scanned based on numerical values which Jeff just started playing with that and has a path to making it work. So smart separations are on the horizon for sure. But all based around HSB color which in theory could be tied into pigments but I am not sure if will get it that far. But being able to scan the color and present smart options for the separation is possible.

I will add here, that we have both the transmissive and reflective densitometer and spectometer. Dialing everything in and getting much closer to the bottom of what our inks are doing and why, is on my list of things to do. Not the next thing, but few steps down the line. I think Mark's software allows some sort of correction (if I remember right) to tweak it for the user's ink system. When Mark was explaining all the features of the software, it was waaaay over my head so I probably misunderstood a lot. If Mark can find some time, it would be great to have a post showing the capabilities and features of ICISS.

How and what exactly to do with the equipment we have is still a little unclear. This thread is definitely shaping a path that leads to understanding what is really going on. I could randomly start taking the readings of what colors are doing when printed, but without truly understanding what is going on, it would be like whacking around hoping to hit the piñata! Systematic and continuous advancement leads to progress, randomly flailing around just makes one tired!

pierre

pierre

[AdvancedArtist]

One other thing.. lets leave opinions and bias outside this has the potential to be a historic thread in this Industry. We have questions we have understanding it is all here right now. Lets be open, honest and lets share.