[argyllcms] Re: Profiling flexo presses

Roberto,

> The big problem in flexo is lack of linearity in
> the highlights, big changes of slope and dot loss at some point which
> I believe is 3% or 5%, don't recall exactly (of course depending on
> linescreen, but usually specified at 133lpi).

Again, all the flexo printers here for which I built press profiles have no
problem maintaining a 2% dot through a run.

> If your friends are routinely printing 2% dots in flexo at 133lpi or
> higher, there is a bump curve.

No bump or transfer function curve anywhere. Imagesetter output is just well
linearized and transfer to plate is constant -- no one looses that critical
2% dot up to the press. And the press holds it easily. That dot gains like
hell (2% to 18% on some systems) mind you, depending on the aniloxes used.

> The digital screened file does not have
> 2% there, for sure.

Of course it does, Roberto! How else would you transfer a 2% dot on film to
plates to press?

> Maybe the curve is implicit in the RIP (there
> are/were dedicated rips for flexo such as the AlanRip), or somewhere
> else you haven't noticed, or maybe it has been applied to the file in
> Photoshop or whatever. There has to be a curve.

The curve in the RIP is only there to make sure that a 2% in Photoshop
remains a 2% on film, a 50% in Photoshop remains a 50% on film, and so on.

> -- Roberto Michelena

Regards,

Roger Breton  |  Laval, Canada  |  graxx@xxxxxxxxxxxx
http://pages.infinit.net/graxx

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