Moire problem from DCS files

[John W]

Re: Moire problem from DCS files

<In fact large moires across the page you can 'see' by virtue that the rosette structure on the screen that you see with FirstPROOF drifts in/out from a clear centered to a dot centered rosette - in fact one of the demo files I was showing at Drupa was exactly this case>

Interesting comment. We are using an older HqRip with great success but recently, I had a job where within the same sheet, I had areas in a four up flat that were clear centre rosette and other areas (same images but different position on sheet) with centred rosettes, thus ruining the look of some of the singles and certainly spoiling about half the job (wasn't seen until after press!). This sort of problem appeared to be basically a crap shoot to find.
By turning the clear centre rosette off at the rip settings, saving and then back on and saving, the problem has not returned. I am assuming some corruption or cache caused this scenario.
Is this sort of 'setting' how you made an adjusting tool for FirstPROOF Andy? Just curious.

John W

 

[Tech]

Re: Moire problem from DCS files

The saga continues...
1) Final PDF files are sent to printer without downsampling but is compressed using CCITT Group 4 to reduce file size from 900+mb to 45mb

2) Blues (low res obviously) comes back with moires and crappy looking, now it's image providers' turn to sign off on the project... suddenly, they are like "what's going on?! we are not signing off on this... there must be something wrong with you press-ready PDF files!"

3) Now I find myself explaining that CCITT compression is lossless on these 1-bitmap files to a bunch of folks whom REFUSED to acknowledge their source image files are not correct to begin with. I like to see how they will link file compression to moires in their files... this one is for the record!


God help me!

 

[Gregg]

"BTW, when viewed @100% on screen bitmap appears cleanly separated as dots and no moires"

I may be way off base here, but perhaps the problem you are seeing is a result of how the bitmap was created?

Do you know if the film was scanned in as 1-bit or 8? You mentioned in one of your posts that the bitmap has separated dots. That can occur depending on what your method is when converting to bitmap. For example, Diffusion Dither will give you many separated dots, while 50% Threshold will give a solid shape.

My theory would only apply though, if the scanned film was grayscale and converted to bitmap, either on the fly, or in P'shop.

 

[Tech]

There is zero info on how images were originally scanned. Lesson learned here, don't trust a provider whom don't even know how their files were created.

In any case, problem is resolved and the answer is wet proof to confirm zero moires.

 

[Jeffrey Guevara]

Moire Problems in Copydot

Moire Problems in Copydot

We would be happy to use our copydot software to evaluate the problem and try to repair it for your workflow. Please contact me at 801-787-7364 Jeff Guevara, Eprep