Banding of photos on output to PDF

[Antony parks]

Hi Guys,

On Output to PDF I am getting some banding, very noticably on the test photos included but visible in others now that I have noticed it on the first.

I'm actually trying to make a catalogue of my paintings that I can print as well as send out with emails. So too different definitions in DPI as I would have output the file at 300 dpi for print and at 144 dpi for attaching to emails.

Screenshot of the culprit picture and the resource manager showing it as 282 dpi on the page:

 

Screen shot of the PDF output from the above page at 144 dpi and viewed at 100% (new ripples across the top of the picture):

I have made a test page and embedded the photo at three different resolutions in the file; see affinity file "Dpi Test at A4 embedded"

The resolution I used were as follows.

First photo is imported at original size from Lightroom and gave a resolution of 566 dpi on the page.

The 2nd version was calculated to give me 300 dpi on the page and actually gives 282 dpi on the page.

The 3rd version was calcuted to give me 150 dpi on the page and actually gives 141 dpi on the page

This test file was output to PDF at 144 dpi see the attached file PDF " Dpi Test at A4 at 144"

In the pdf the banding is most noticable from the highest definition photo and almost eliminated in the lowest definition.

In short this seems to mean that I will have to calculate each photo in the catalogue twice; once for print and once for email.......

Am I doing something silly or is there a real problem?

All help appreciated,

Antony

 

 

 

 

 

Dpi Test at A4 embedded.afpub

Dpi Test at A4 at 144.pdf

[thomaso]

I see a moire in your PDF. That might result from a rasterized (printed) image which got scanned or photographed. Could you upload the original image (before any edit)?

[Antony parks]

Hi Thomaso,

The original is a DNG photographed directly from the original painting. So for ease of viewing; the attached is Jpeg copy with no edits.

Yes: you are right. The ripples are the interference patterns caused by the weave in the canvas of the painting. However I have never had this problem before.

The originals for my catalogue are all (before any crop) 18 mega pixel, photographed with a Leica. The photos are all taken in natural diffused sunlight. They are tranferred and catalogued in Lightroom (LR 5). Here I check white balance ( using color checker), exposure, sharpening (no sharpening in DNG) and sometimes soften or enhance the coulours. They are then cropped to the canvas. But they still remain as DNG at this point. They are then out put to Jpeg when I want to go to print or to my website or posters or small flyers or business cards or whatever.

Previously any print or publicity preparation was done in Adobe....but I have been working exclusively with Affinity (except for Lightroom) for just over a year and this is the first time I have had this problem when outputting to PDF. I have not had to resize the photo files when I was using the same layouts at different out definitions.  This time I have had to make two different Affinity files with different sized originals. In the "web size file" all the originals have now been output to be 144 dpi aprox on the "page"; this worked I have no interference patterns.

The PDF attached is another page where the original has been has been left full size that is then reduced to 144 dpi in Affinity publisher export. Ripple patterns again.

To my amateur eye there seems to problem with Publisher's size reduction when outputting to PDF.

The same problem to a lesser extent is happening when I output the same page to Jpeg at 144 dpi. Have a look at the "Mariquitta Jpeg 144" file below on a decent screen.

I surprised other people have not had this problem. Or does everyone know about it and make their reductions else where?

Anyway I've made my two files (one big and and one small) so I'm up and running.

Have a nice evening ,

Antony

 

 

 

 

Mariquitta test.pdf

[thomaso]

I see just a very natural effect on screen, nothing wrong with your images DNG or scaling (edit, see next post). This effect does not appear when you view and/or print the file in large size but may occur in a lot smaller size:

As you mentioned this waveform pattern is a interference moire as result of the combination of a.) the canvas texture and b.) the monitor pixel grid. So it occurs only in specific zoom level and/or specific combination of image size (canvas grid) and screen resolution (pixel grid).

You can avoid this effect only either by excluding specific grid size combinations, means for only view to choose a image size where the canvas grid is very close to or a multiple of the monitor grid (while different monitors have different pixel sizes) or of the print screen frequency. Another option would be more manipulative by softening the image to reduce the canvas structure without touching the painting's contours.

To avoid this effect for future photos you could try to make sure to get light with no direction. In the current photo you can see an obvious light direction from the upper edge, that makes the lights and shadows in the structure more obvious:

 

[thomaso]

You can measure/calculate the screen values of both the canvas structure in your DNG and any wanted output size, either on monitor or print (which both use different screen frequencies /or none with some particular print technologies.) When you know the screen values (eg. 70 x per inch) you can calculate according output sizes which prevent the moire effect.

This article gives a short well illustrated info, in particular a note about How to avoid:

Tips for avoiding screening moiré
1- Use FM/stochastic screening for the yellow printer. If you're using a 150-200 lpi AM/XM screen then use a 35 micron FM/stochastic since it will have a similar dot gain curve.
2- Make sure that incoming halftone screened bitmap files have a resolution that is equal to or an even divisor of the resolution of the output device. Make sure that those bitmapped images have not been resized in a page layout application.

Tips for avoiding resampling moiré
1- Import images into page layout applications at 100% - do not resize in the application.
2- Images should have a resolution that is an equal divisor of the output device. E.g. 300/400/600 dpi are even divisors of 2,400 dpi.
3- Make sure that PDF creation applications are set to not resample images.

https://the-print-guide.blogspot.com/2009/12/moire.html

 

 

[Antony parks]

Hi Thomaso,

Thanks for taking so much trouble over this.

I will read the article with interest.

Tips for avoiding resampling moiré
1- Import images into page layout applications at 100% - do not resize in the application.

It is this problem that I am getting: the interference pattern is being generated in the reduction when I output to PDF in Publisher at 144 dpi. The moire is actually "inprinted";  it is not a viewing effect on the monitor/ ipad/ telephone  screen. I have to make reductions in some other software and bring them into Affinity Publisher at 144 dpi if I want to output at 144 dpi.

This means that print output files and screen/internet output files are not simple reductions the one from the other and anything done for print needs to redone for internet.

But there is something strange: why does Lightroom give me a reduced Jpeg without interference patterns when both Affinity Publisher and Affinity photo produce inerference patterns?

The attached file was reduced in Affinity Photo and has moire inprinted into it. It is a reduction of the original at 4012 on the long edge to 1020 on the long edge.

Anyway have a good day

Antony

 

 

 

 

 

[thomaso]

4 hours ago, Antony parks said:

The moire is actually "inprinted";  it is not a viewing effect on the monitor/ ipad/ telephone  screen. I have to make reductions in some other software and bring them into Affinity Publisher at 144 dpi if I want to output at 144 dpi. 

This means that print output files and screen/internet output files are not simple reductions the one from the other and anything done for print needs to redone for internet.

Yes, I see your point. Unfortunately it is kind of a physical issue, not of Affinity. You can prevent it only by avoiding those particular image sizes where the moire occurs. Naturally if you create the image in an affected size you "burn" the moire into the file and make it even appear that way even if that file will be viewed in a different size then.

4 hours ago, Antony parks said:

But there is something strange: why does Lightroom give me a reduced Jpeg without interference patterns when both Affinity Publisher and Affinity photo produce inerference patterns?

I assume that it is related to different algorithms when the image is scaled (= resampled). Possibly Affinity produces different results when you export with one of the five resampling options available for both .jpg and .pdf export:

This post of Gabe (Serif) shows a quick comparison of those 5 algorithms. (though the issue + sample image wasn't related to moire)

Finally, may be you can get more detailed support in this recent thread (– since we are here in the bugs forum):