wrong reading plate...

[mazengh]

A press house is requesting wrong reading plates, so our prepress have been supplying them wrong reading 1 bit tiffs. Any valid reason why they would ask for that?

 

[kyle]

I would expect that they could handle that easily enough, as long as there is no ambiguity in the image preventing them from knowing which way it should be (like a spot varnish plate with a knockout area and no text). If they are making film and want to have the emulsion on the opposite side as their workflow/device expects it to be on, then mirroring the image effectively puts the emulsion on the other side.

From what I remember, the emulsion is usually "down," meaning that when you look at film right-reading, the surface facing you is the clear film and the back side is where the emulsion is. If you wanted to etch a clear mark in the film, you would do it on the emulsion side. The film is placed emulsion-down on the plate and the plate is exposed. If the film were made emulsion-up (by mirroring the image), the light would spread a little bit through the clear film and create a bit of trapping. If you make two spot color plates that don't have screens, and the colors touch, and there is no trapping in the film image, you could make the lighter color emulsion-up to crudely create trapping.

If a printing process is non-offset (maybe flexo?), then the plates would need to be wrong-reading. If the plates are made from film, the film would probably need to be emulsion-up. Either way, the image given to the imagesetter/platesetter would be a mirror image of how it would otherwise be if the plates were right-reading as in offset litho.

 

[SteveAgfa]

How about if they are printing on the back-side of clear plastic for signage?

 

[mazengh]

offset printing...

offset printing...

I might have forgot to mention that it's for offset printing...

 

[SteveAgfa]

Actually, I've seen offset on white plastic, printed same image both sides,
the reversed flopped, for for back-lit displays; the colors are richer. We see
this too with wide-format.

 

[mazengh]

Actually, I've seen offset on white plastic, printed same image both sides,
the reversed flopped, for for back-lit displays; the colors are richer. We see
this too with wide-format.

Steve, did you mean a white plastic substrate on which you print surface on one side, and same content printed reverse on the opposite side? so the result of printing surface and reverse generates the richer colors? has to do with light filtering? Also is this for indoor prints? since it's printed surface so it's not scratch resistant....

 

[SteveAgfa]

mazengh:

yes.

 

[melissa]

Jet envelope presses require wrong reading plates for copy that is printed on the back or flap side of an envelope. This applies when only printing on the back side also. At least our press operators request it that way.

 

[Alois Senefelder]

wrong reading !!

wrong reading !!

Hello, maybe they require these plates for printing by "Direct Litho"


Regards, Alois

 

[mazengh]

direct litho?

direct litho?

what applications is that good for? what type of plates?

 

[Alois Senefelder]

Direct Litho # 2

Direct Litho # 2

Hello Mazengh,


Enlightenment -- some PDFs

re - type of Plate, most commercial makes are OK


Regards, Alois

" From knowledge to competence is a great step ---- from ignorance to competence an
even greater one "

 

[michaelejahn]

Inverted upside down (bat reading) orientation

Inverted upside down (bat reading) orientation

A press house is requesting wrong reading plates, so our prepress have been supplying them wrong reading 1 bit tiffs. Any valid reason why they would ask for that?

I can think of several, with the most obvious being that they have a filmsetter in the workflow and expose plates - or some platesetter that requires it.

Why would you care one way or another - now if they asked for bunny shaped dots, well, I would ask, but if they want wrong reading upside down or backwards/inverted, mirrored 1 bit TIFFs, I would simply provide them 'for an additional fee'

(wink)

Please do ask the customer and tell us why

 

[KevinC@EFI]

As mentioned before, "Direct Litho" is a likely answer too - essentially printing with no blanket between the plate and paper (plate is in direct contact with the printing substrate).

We see that from time to time for some unique applications - usually things like directory printing, etc. It's very hard on the plates themselves, and usually for cold-set web. Typical cold-set web plates like ThermalNews Gold, etc. usually perform well, but with less runlength due to the much higher physical abrasion in such an application.

Having said all that, I do not know what the actual printing benefits of direct litho are supposed to be - besides the elimination of the blanket. I would expect you'd carry more water to the paper too.

Kevin

 

[gordo]

Hello Mazengh,

Enlightenment -- some PDFs

Regards, Alois

" From knowledge to competence is a great step ---- from ignorance to competence an
even greater one "

With all due respect, I think "Enlightenment" requires the "why" and not just the "how." `{]

thanks, gordon p

 

[claude72]

From what I remember, the emulsion is usually "down," meaning that when you look at film right-reading, the surface facing you is the clear film and the back side is where the emulsion is. If you wanted to etch a clear mark in the film, you would do it on the emulsion side. The film is placed emulsion-down on the plate and the plate is exposed.

You remember correctly.

If the film were made emulsion-up (by mirroring the image), the light would spread a little bit through the clear film and create a bit of trapping. If you make two spot color plates that don't have screens, and the colors touch, and there is no trapping in the film image, you could make the lighter color emulsion-up to crudely create trapping.

Correct with negative plates: if the emulsion is up, then it is not in contact with the plate and the black areas enlarge on the plate with hazy edges... thicker is the film between the emulsion and the plate, bigger is the enlargement.

(In the old days of manual stripping, it was the way used to create trapping on positive films, simply by adding a clear foil (or some clear foils) between the negative film and a negative blank film, in order to raise the spreading of the light, and over-exposing to compensate the bigger thickness to be exposed and to make the edges of the spreaded light more efficient.)


But with positive plates (used in europe), if the emulsion is not in contact with the plate, then the white areas enlarge on the plate, and the black areas are reduced... meaning that screen dots will be reduced, and the lower values will be completely "burned" and will not appear on the plate...

Having said all that, I do not know what the actual printing benefits of direct litho are supposed to be - besides the elimination of the blanket.

An example... Some years ago, when I begun in offset printing, the print-shop had a little A4 offset press with only 2 cylinders: plate holding and pressure was done by only one cylinder twice bigger in diameter than the blanket cylinder...
- the plate was hold on the first half part of the circumference,
- and the second half part of the circumference was covered by a steel sheet acting as pressure area (and also protecting the cylinder, like on a GTO's pressure cylinder)...

1° in the first half turn, the plate/pressure cylinder acts as a plate cylinder with its first half:
- the dampening and inking rollers were applied on the plate, deposing water and ink on the plate (I don't remember if dampening and inking was separated or mixed... sorry),
- then the inked image of the plate reported on (almost) the whole circumference of the blanket cylinder (because the diameter of the blanket cylinder was half of the plate/pressure cylinder, so the blanket cylinder turned one turn while the plate/pressure cylinder turned only half of a turn)...
- and at the end of the half turn of the plate/pressure cylinder, the dampening and inking rollers were raised to avoid touching the plate...

2° and in the second half turn, the plate/pressure cylinder acts as a pressure cylinder with its second half:
- a sheet of paper were brought,
- and pressed between the blanket cylinder and the steel sheet covering the second half part of the plate/pressure cylinder.


But it was possible to replace the pressure steel sheet on the second half part of the plate/pressure cylinder by an offset plate, then an action on a lever made the dampening/inking rollers stay applied on the cylinder during all its turn, inking/dampening the 2 plates successively, and during the second half turn of the plate/pressure cylinder the sheet of paper was printed:
- as usual on its front side by the blanket and its image of the first plate (or "front plate")
- and on its back side directly by the second plate (or "back plate") with "direct litho" system!!!

... and, of course, the "back plate" had to be wrong reading!!!

 

[Alois Senefelder]

The Why !

The Why !

Hello Gentlemen,

The Why, just a practical reason in many Local Newspaper Printers they had a limited amount of Press Units to print with, printing direct on some units allowed larger pagination.

No advantage print wise - using "Direct Litho" in fact it was a "Pain" at times. -- One Press Unit printed 2 Colours on 1 side the next Unit printed the other 2 Colours same side

Regards, Alois

 

[KMGI Sales]

Alois you are exactly correct. As a matter of fact I see that daily at alot of our newspaper accounts, for that exact reason. The big problem with this however is the dot gain you receive when printing direct. Which is why it typically falls on Yellow to print direct as its easier to hide, although I have seen it on Cyan and Magenta too in more than one case.