Printing Gray and Black

Hi,

I searched this forum for everything duotone and gray ink related and although I found a fantastic amount of information I still have one question remaining. I am printing a b&W photo with a black ink and a gray ink. Rather than create a duotone in Photoshop I am manually separating the photo into 2 images (one for gray ink, one for black ink) and then compositing them together in Indesign. My question: how do I adjust the curves/levels in order to create the 2 versions?

 

Sorry if that was confusing.

In this example:
50% prints 100% with the gray ink.
50% prints 0% with the black ink.

Is this correct? The gray ink is cool gray 9u, which is roughly 50% black.

 

I recommend cool gray 10 as a starting point. You can always make cool grey 10 lighter by adding transparent white but you can't go the other way. Also be sure to adjust the screen angles to avoid moire pattern.

 

Thanks for the recommendation.
Maybe cool gray 11 would be even better.
If i run the screens at the same angle i should be fine, right?

 

Why not you print both colors with different screen angles?

 

Would that be better?

 

When running two colors with the same screen angle, there is always a chance of moire pattern and with slight register deviation it will change the desired color.

 

heres your BEST option.... buy cool gray base and adjust as needed with transparent white. The cost of the cool gray base should be no more than the cost of any of the pre mixed cool gray colors, and you just add trans white which is the least costly ink. Then you have the remaining cool gray base for future use as you see fit.
Also you must run different screen angles with duotones!!!

 

Ah, OK. I'll do different angles. I'm not actually printing this – just designing it. Probably not a good job for a cheap printer in Hong Kong, huh?

 

A Belgian printer responds, "Your curves are much too brutal, you cannot erase information from 0 to 50% in the blacks, and certainly not 'shut down' from 100 back to 50% in the grays."

 

you can use the same screen angle if you change the screen rulling
try the black at 133 and the gray at 175 and you will get an interesting effect

 

i think you're trolling

 

Not at all.
when you use different screen rulling , you can not get Moare.
check it out , but trust me , i know something about prepress & printing

 

ah, ok! thanks for the advice. i know very little about these things.

 

but you still call other a @troll@ without checking ?????
Good for you

 

Just to throw a curl ball in. What type of screens do you use in plate making ? Most of the shops I go in are running FM screening and there is no need the set an angle. But if your running AM you must have a 15• or 30• difference from the black.

FSA

 

I don't like the look of FM screening, even though the picture is more detailed. I assumed AM/FM was just always an option. i assumed it was sort of arbitrary whether the image was converted to bitmap (in the RIP i'm guessing) as dots or noise. 15 & 30 is good to know, thanks! Prepping artwork for 'duotone' (not duotone, but whatever you call a grayscale image printed in 2 colors) is a lot more complex than i thought so I'm going to just go with 1c (black) instead. i'm still interested in this subject, so any other advice would be helpful.

 

Hey to each his own, I like fm screening a lot and no moray patterns. To do what we print in fm screening the am screen would have to be 250 -300 line per inch. And how clean the images are,the customers are happy.
Well good luck and keep learning, this industry is changing. If you can get you job printed on a DI machine you will get your am screen and they run an good 300 line

FSA