Dot Shape Effect On Images
- Thread starter printryt
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gordo
Well-known member
You are posting the same question in different topic areas which can make it difficult to follow the answers you get.
The best AM/XM dot shape for offset CtP is the round dot (a.k.a. non-transforming round dot.
Quality In Print: AM Screening Dot Shapes
This is because the dot shape is the same for all screen angles and frequencies. The optical bump is hidden in the shadows at the 75% tone. It reduces/eliminates single channel moiré issues. Dot is non directional, i.e. all screen angle dots react the same to directional press issues such as slur and doubling
More info on dot shape options is available here: Quality In Print: AM Screening Dot Shapes
I don't know what you mean by "sharper" as that term has many different meanings.
If you mean sharper as in what happens when you use the sharpen filter in PShop then the only screen I know of that does that is the square dot. But that is rarely used because it has litho problems on press and sharpening in PShop is more efective.
If you mean sharper as in less dot gain - well it's much better to deal with dot gain through the use of compensation curves applied when imaging the plates.
best, gordon p
thank you for your reply.. when i said sharper, i meant the images would look very lively and not dull or dark...
another thing. i'd like to ask what STANDARD CURVE (print calibration) would you recomend, since i am providing service for different offset printers?
do you have values for the curve (based on your experience)?
another thing. i'd like to ask what STANDARD CURVE (print calibration) would you recomend, since i am providing service for different offset printers?
do you have values for the curve (based on your experience)?
gordo
Well-known member
The shops that I've worked with that supply plates to printers work closely with those printers to establish the appropriate plate curves - custom tuned for each shop.
If the printer is running 175 lpi at industry standard solid ink densities you could start with linear plates and in most cases that will work. Might not be the absolute best - but will work more often than not.
To be really successful though you need to act, and they need to treat you, as if you were an internal prepress department rather than just a source of plates. That way you can work with them to create plates that are optimized for their presswork target(s).
When you say that the images should look "lively and not dull or dark" you are talking about the result of separations, plates and presswork. Those factors have way more impact on final print quality than the subtle impact of the shape of the dots.
Start with an agreed color target. E.g. GRACoL7.
Create a proof that represents that target.
Then work with the printshop to create create plates that allow the printer to hit that target proof with their presswork.
best, gordon p
gordo
Well-known member
That becomes complicated.
You need to determine whether the dot loss is caused by the press condition or the plate imaging (or a combination of the two). If you have several customers experiencing the same problem then that suggests it's probably a plate/plate imaging/processing issue. Best to bring in your CtP/plate vendor to find and correct the cause.
best, gordon p
Sorry for my very very late reply.. we already found the solution to our dot loss a long long time ago.. i think around the time i stopped checking this forum... we just had to do some adjustments in our machine and that's it.... no more dot loss... no more down plates... no more head aches hehehehe
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