CTP plate dots

[Nishanth]

I would like the dots on our CTP plates to be round or any other exact shape.
Unlike round, some are square, triangle, elliptical.
And the same shape is being printed on the paper. We use Screen CTP.

Can anyone guide me to achieve what ever the shape i needed on the plates?
Thanks in advance.

 

[elece]

What workflow you use?
You can change the dot shape through the workflow.
With ElecRoc I can select: Round, Ellipse, Rhombus, Diamond, Square, and another ones i have never use.
With ApogeeX you can choose Roun or Elliptical
In both cases you can change it in the same window you change angle or lineature
Other workflows I supose works similar

 

[prepressing]

Check out the Harlequin RIP's screening:
Harlequin Precision Screening in the RTI Harleuin RIP

There are lots of options for different screening including Hybrid, Stochastic, Chain, Micro, Digitally Modulated, etc. Round is one of the standard dot shapes included with the Harlequin RIP.

 

[maxon]

Nishanth,
1. What RIP do you use ?
2. What resolution do you use for exposing plates ?
3. Do you have a preview of the screened data available before sending out the job to ctp ?

Irregular dot shape may be caused by hardware problems i.e. bad focus, too low physical resolution 1200 being used instead of 2400 or better, vibration-induced distortions affecting imaging quality a.s.o. or software.
Most of today's screening algorithms are based on supercell halftones, you will rarely see perfect shaped dots - round as round, perfect checkerboard for 50 percent square etc. Check Adobe's Technical Note 5602 way back in '97, also Gordon's qualityinprint.blogspot.com about grey levels and supercell concept.

 

[Printservedigital]

Irregular dot shape may also be caused by dirty lenses.

 

[SZmetana]

What area are you looking at?

What area are you looking at?

Hi Nishanth,

In what areas do you see a variety of shapes? In a "flat tint" area, an area which has exactly the same tone? (Such as a square of 30% black?) Or are you looking into a color halftone area?

I would be surprised if Screen produces dots that are any less Round or Elliptical than any other manufacturer in an area of uniform tint. Screen has been doing digital screening for 30 years or more, and understands screening very well. (I used to work on a Screen Sigmagraph system in the early 90's, and it produced top-quality screening.)

I suspect you might be looking closely at a small area of a color halftone, in which dots from different colors overlap different color pixel boundaries in the underlying color image. You will see many strange shapes and partial dots in these areas, as the result of overlaying a 1-bit screening grid at 2400/2540 dpi over an 8-bit color separation at 300 dpi, or similar. It's simply what happens when the dots are trying to faithfully reproduce the color changes in an underlying color image. Every workflow produces the same results, in this respect.

Do you have a new TIFF viewing tool that allows you to see a digital bitmap up close for the first time? Maybe it's not a case of being bad, but just being different from what you expected. What are the results like on press?

 

[Printservedigital]

This is where a Teckon Densitometer comes in handy

 

[Printservedigital]

"I would like the dots on our CTP plates to be round or any other exact shape.

"Unlike round, some are square, triangle, elliptical."

You're looking at the product of a collection of "dot's" and not the "dot" single laser exposure then as I would interpret it.

In regards to "dot" creation as you understand it I have witnessed a perfect elliptical dot on a Kodak Violet plate produced by a second generation Laserjet LSjetII (Krause) at Krause's research facility in Germany in Biederfeld over 6 years ago in 2003/4

 

[Nishanth]

Clarification needed

Clarification needed

Firstly thanks for your replies.

Actually, when all your instructions are what we following now, still our dots are very irregular shaped.

We use the Harlequin to rip. We use 2400 resolution to expose the plates.

Please go through the attachments for the snapshot of the dots on our plates.
One is our plate and the other one is the Fogra wedge which look perfect.



Kindly suggest me.

 

[Printservedigital]

Yours look ok to me, I suspect that's a 50% is it not? with the fogra being Higher!

In fact your can see some irregularities in the larger dots on fogra sample as well , have you actually measured it?

Are those white small dots all over the plate from the camera that you used to take the photographs with, that would concern me more actually.

And your also your plate isn't cleaning up properly there are areas of "Dark" dots on the larger dots that I would be looking at investigating.

The dot shapes themselves look ok, it the irregular white and dark bits that I would bee looking to correct more that the dot itself.

 

[SZmetana]

Dot Shapes

Dot Shapes

I think this must be your first experience of looking at printed digital halftone dots through a microscope.

These are completely normal printed offset dots. In fact, they are pretty good quality. If you saw the same dots printed flexo, they would look much more irregular.

A digital halftone dot is made up of discrete pixels. At 175 line, 2400 dpi, a 60% dot (what I estimate these printed dots to be) is only going to have around 9 x 9 pixels available to make the curve of the dot, and it's easy to see the steps of these pixels.

When you add the fact that the dots gain slightly due to ink spread, and that this spread will be varied, depending on the grain and roughness of the paper at the microscopic level -- what you see is a completely normal appearance for printed halftone dots.

 

[gordo]

To Nishanth:

You've posted this question before with the same two images. The answer remains the same.
The smaller the dot the greater any difference in dot shape you'll see. The larger the dots the less difference you'll see. You should compare halftone dots that represent the same tone value instead of these different dot areas.

Also you should compare screens of the same frequency and angle which these also don't appear to be.

BTW, why are the dots and plate colors so different?

You seem to be comparing "apples and oranges"

best, gordon p

 

[mannyx]

To Nishanth:

can you specify sir if the fogra image is produce using film and the 150lpi is expose in ctp process
base on my observation the 2 images you send is produce in a different process... gordon is right
you cant compare apple to orange... as far as the dot shape is concern...

thanks,
Manny