Moire appears after PDF export

[kathleend82868475]

I'm laying out a book with many TIFFs of paintings - when I export to PDF, a moire pattern shows up in three of them.

The moire doesn't show up in inDesign unless I'm at 100% - it's gone at all other resolutions.

The moire doesn't show up in PhotoShop unless I'm at 33% - otherwise gone.

The moire shows up at all resolutions in the PDF.

I'm using PDF/X4:2008 for export. Is there something else I should be doing?

Another question: Will the moire show up in print if I do nothing?

I'm running inDesign 18.5 and Acrobat Pro 2023, OS Ventura 13.6.1 on a MacBook Pro.

[Jeffrey_Smith]

Is the digital capture of the original painting or a lithographic reproduction?

If it is a litho, there will be a very fine line screen, hardly seen with naked eye, but would be seen under magnification. And yes, this could cause a moiré in the print process. A possible solution to this issue would be to add a slight amount of noise to the image in Photoshop.

[kathleend82868475]

The TIFF of the painting came from a photo taken in the studio, so no reproduction of any kind.

The texture of the underlyin canvas shows through in some of her paintings, and I wondered if that's what was causing the moire. Was hoping not to alter the image in any way, but it sounds like I better.

[Jeffrey_Smith]

The screen capture shows considerable compression artifacts. I realize this might be the image you posted. What kind of image compression is applied to image. You should use LZW. If need be, do you have access to a raw image? Also, in the PDF export process, you may want to test a PDF that does not compress images.

As for the print side: what is the print method: digital or offset? Do you know if your print provider offers stochastic or random dot screening?

[kathleend82868475]

Yes, the TIFF uses LZW compression. I don't know if I can get the raw image - all the photos in the book were done by a photographer the artist hired and were done over several years' time as she created the paintings.

I'll try other PDF export settings - also will speak with the printer as soon as the artist settles on one she likes.

[rob day]

The texture of the underlyin canvas shows through in some of her paintings, and I wondered if that's what was causing the moire.

hi @kathleend82868475 , Have you proofed the art to a high res printer? Your description of the moire coming and going at different magnifications indicates it's coming from the display resampling needed to preview at different magnifications. Do you see it in Photoshop at the 100% or 200% view?

[Robert at ID-Tasker]

Have you tried to simulated raster in Photoshop? 

[kathleend82868475]

I'm not familiar with simulating raster - the TIFF is already a raster image. "Raster" is greyed out on all menus. ?

[Robert at ID-Tasker]

If you know angles and what kind of a raster will be used - you can use Photoshop to simulate each plate - I'm sorry but I'm on the phone so can't give you more details. 

[Robert at ID-Tasker]

OK, here is a rough process:

1) you need to export your file as separate plates - Cyan, Magenta, Yellow, Black.

2) import each plate as a separate file - Grayscale Mode,

3) convert to Bitmap:

Select correct Shape, Angle and Frequency:

4) you'll get something like this - B/W newspaper:

5) do it for each Place / Channel - with correct Angles,

6) then you need to copy each "plate" into a new file - into a corresponsing Channels in CMYK Mode.

You can record this as an Action so you can quickly use it next time.

Of course, it won't be exactly the same as bitmaps extracted from a RIP...

[kathleend82868475]

Thank you very much for this -

[RvdT]

Is your image (psd) scaled in inDesign?

If yes. Make the image 300 dpi at the actual size. If there isn't moire visible at 100% in Photoshop there shouldn't be any in inDesign or Acrobat at 100%.

If there is a difference in Acrobat at 100% you need to check your image resample settings in inDesign (pdf export settings).

[Jeffrey_Smith]

Placing the image at 100% will absolutely help this possible issue.

[kathleend82868475]

Thank you - I redid this without any scaling this time - see my note below to Rob Day -

[rob day · Accepted solution]

I think it is safe to say the moire is from the screen display resampling—the resampling that has to happen in order to preview the image at various magnifications—and is caused by the canvas texture interference in the painting.  I have two displays running at different resolutions, and it’s difficult to find a magnification where it happens on my high res retina display, but happens at a number of magnifications on my low res cinema display. Here it is placed in Indesign at 90% on the low res display:

And on the retina display:

The moire is not in the file, so it’s unlikely to happen in print:

[kathleend82868475]

Thank you - as soon as the client chooses her printing house, I'll ask the printers to run a proof of the three images. I'm very hesitant to touch them if I don't have to (such as adding a blur, which some have suggested doing) - artists don't like anyone touching their work - so if it's a display issue, that would be the best outcome.

[rob day]

You might ask the printer if they can run a stochastic screen rather than a halftone—takes more skill, but there wouldn’t be a moire because the screen pattern is random.

[Jeffrey_Smith]

Moires are caused when 2 different patterns are present: the first is the canvas pattern, the second will be the line screen in the print process.

A digital hard copy proof will most likely not be 100% reliable for this issue. The only way to verify whether a moire will or will not be present is with a process that uses the actual half tone dots, and a press proof is one method. Unfortunately a press proof is very expensive, and not feasible to produce.

[kathleend82868475]

The printer did a 10-page sample for us of the moire-ish images - no problem in print. It was all onscreen. Thank you all for your help.

[rob day]

Can you share the TIFF you are placing?

[kathleend82868475]

I've attached the TIFF. The moire doesn't show up in PhotoShop at any resolution. It also doesn't show up at 100% in inDesign, but it does show up if I go down to 75%:

inDesign 75%

I originally did do some scaling after placing it - in this latest version, I've placed it at 100%, and the resulting PDF has less moire though still some.