Are we using Sublima?

[Paul Mumford]

Hello everyone, our company has recently been upgraded from Apogee 2.x to the latest version. From the following screen grab of a hot-ticket plan, could anyone confirm whether we are using Sublima or not?


According to the agfa engineer who installed the kit, ABS H2S4 is Sublima?!?
According to another agfa engineer AzuraV plates don't support Sublima?

Any help would be great with this conflicting information. Thankyou in advance.

(We previously used Sublima 200lpi on our old system and plates.)

 

[Lukas Engqvist]

The hybrid rasters are very similar to the sublima technology H2S4 means the smallest dot size is 2x4 cells on your image device, if a smaller dot is required it will "dither" 2x4 dots to produce the correct coverage. This is very similar to how sublima works, I think AGFA defines sublima as being above 200lpi though. This is not a technical high reliability explanation, but a user experience why technical experts may disagree on wether ABS H2S4 is sublima. Again it is a HYBRID raster.

 

[Paul Mumford]

I see, thank you very much. We are getting better results with this screening so far but it's early days. I just wanted to be able to give a definitive answer when asked again by my boss.

 

[gordo]

From the following screen grab of a hot-ticket plan, could anyone confirm whether we are using Sublima or not?
According to the agfa engineer who installed the kit, ABS H2S4 is Sublima?!?
According to another agfa engineer AzuraV plates don't support Sublima?

(We previously used Sublima 200lpi on our old system and plates.)

Yes, ABS H2S4 is :Sublima.

ABS means Agfa Balanced Screening which is Agfa's standard AM screening (the first option in your list). H2S4 designates the minimum highlight dot size that ABS will restrict the screening engine to produce. That restriction to a specific minimum dot size is used to recover tones that would otherwise be lost due to resolution limitations in the imaging system - plate or press.

The AzuraV plate resolution is 2-98% at 200 LPI depending on imaging conditions so you should not need to use :Sublima if you are running 175 lpi. Use ABS instead. If you are having trouble holding a 1% dot at 175 lpi then you can consider using ABS H2S4 instead.

best, gordo

 

[Paul Mumford]

Ok thank you, the AGFA engineer left us setup with:

ScreenType: ABS H2S4, Frequency: 175 DotShape: Round.

There is no option to change to a frequency of 200 with the ABS H2S4 selected. Does that sound correct? Thanks.

 

[Lukas Engqvist]

I think you need to install the hybrid rasters at the different resolutions, so the 200 lpi H2S4 needs to be installed separately in the system for you to be able to use it (it's a few years ago I had access to a system) To install a screen you need to be service or at least admin user and on a PC, once the screen is installed you can select it.

(Gordon describes it as the plate not holding the point... in my experience it is the stability of the point on the substrate that determines the screen to be used which is why we used a different minimum dot threshold size for coated, semi-coated and uncoated. This was based on empiric tests so I have no theory to back it up)

 

[gordo]

[SNIP]

(Gordon describes it as the plate not holding the point... in my experience it is the stability of the point on the substrate that determines the screen to be used which is why we used a different minimum dot threshold size for coated, semi-coated and uncoated. This was based on empiric tests so I have no theory to back it up)

You don't need empiric tests or theory. The specifications for Agfa CtP state that their plate/output devices cannot image a 1% dot at an lpi over 200. I.e. they have a 21 micron resolution limitation (4 pixels - a 1% dot at 240 lpi is 10/10.6 microns - one pixel). Hence their requirement for :Sublima for screening over 200 lpi.

On the other hand, a sheetfed offset press in practical production condition can consistently image a 1% dot at 240 lpi on both coated, semi-coated and uncoated papers if the dot can reliably be imaged by the CtP and plate.

best, gordo

 

[KevinC@EFI]

You don't need empiric tests or theory. The specifications for Agfa CtP state that their plate/output devices cannot image a 1% dot at an lpi over 200. I.e. they have a 21 micron resolution limitation (4 pixels - a 1% dot at 240 lpi is 10/10.6 microns - one pixel). Hence their requirement for :Sublima for screening over 200 lpi.

On the other hand, a sheetfed offset press in practical production condition can consistently image a 1% dot at 240 lpi on both coated, semi-coated and uncoated papers if the dot can reliably be imaged by the CtP and plate.

best, gordo

Holding a dot on plate is also not necessarily the same as holding it on press - especially through the full print run. Smaller dots wear faster (of course), and the "profile" of the laser exposure may greatly affect how strong the edges of the dots are and how quickly they'll wear. When you get into these realms, there's a huge difference. As Gordo knows, this is the whole reason we can do 10-micron printing (and hold 1% dots at 240lpi) with the SQUAREspot head.

Kevin.