Staccato Screening - printing 4col Black and white images

[HW]

Hi All

We have proofed a job to Fogra 39 - The 4col B/W Photos look great (maybe lacking contrast, which is due to the epson, but the photos look neutral)

All our press curves are targeted towards ISO Dotgains. We put the Job on press, using image control we levelled the sheet to ISO coated LAB Values.

Here'e the problem, the neutral B/W now looked sepia. I have a feeling because we are printing staccato, the grey balance is harder reach - Am i right or is this total rubbish and something else is wrong.


Hope this makes sense

 

[JRom]

Re: Staccato Screening - printing 4col Black and white images

Are your plate curves targeted to ISO conventional screening ? Staccato will require its own custom curve set.

What area is going sepia ? the whole tonal range or just one area ?

Normally with staccato the Highlights and Quartertones get sharper and you will get more gain in the 3/4tones and shadows.
So your getting an increase of contrast with the FM screen.

I don't normally see yellow gaining more than the other colors though, usually Cyan and Magenta are higher.

John

 

[HW]

Re: Staccato Screening - printing 4col Black and white images

Hi John

Our Target curves are based on ISO, which i believe are based on 175screen conventional. What targets do I run to for staccato ?

Just the photo is going sepia ?

I have attached some files to look at.

File 1 - LoRes PDF for visual

File - High res file of just B/W image.


See what you think !!

Edited by: Dan Marshall on Jan 22, 2008 7:44 AM

 

[JRom]

Re: Staccato Screening - printing 4col Black and white images

Hi Dan

Didn't see any attachments there but you should adjust the gain of your FM to match the gain of your conventional screening.
That is If your proofing is aimed at conventional screening......

Your probably going to have to have a positive / increase in your highlight to quartertone and should be
reducing from the Midtone through the shadow.


John

 

[gordo]

Re: Staccato Screening - printing 4col Black and white images

Dan,

John is correct. Staccato, like any other high frequency screen, will have a different tonal response compared with 175 lpi. You should make the 175 lpi on press tonal response your target and use plate curves to align your Staccato. You may also need to adjust the final curves slightly to achieve gray balance. That is because the hue of different process colors change when they are printed with small dots thus affecting gray balance compared with a 175 lpi screen. A small curve adjustment will easily restore proper gray balance. Also, you may want to consider heavy GCR for your separations - again to provide better neutrality and color stability on press.

best, gordo

 

[disbellj]

Re: Staccato Screening - printing 4col Black and white images

I've seen a brown/sepia appearance when the numbers in my file were equal CMY (where all equaled 50, instead of Cyan being 50 and Magenta and Yellow being 40 each). Could this be what's happening? If it's not the file, I would say it's the plate curves that are making the same appearance, probably again by Cyan not being higher than Magenta and Yellow, but all three being the same. With a densitometer, the gray patches should read the same neutral density (same number for all three, within tolerance). If this is the case, the plate curves need to be set up so that the wanted TVI values are obtained when you get to the target Lab values (again, within tolerance) for solids/overprints on press. Just my thoughts. Hope this helps.

Don