CMYK JPGs do not compress when making PDFs (PDF/X-3)

[waltonmendelson]

I am using Affinity Publisher ver. 1.10.1.1142 with Windows 10, fully updated.

Problem:

JPGs in CMYK do not compress when compression is applied when making a PDF (PDF/X-3) in Affinity Publisher: even down to 0! That is, in this case, the PDF made from the smaller JPG, was 2.891MB with the slider at 100% and at 0%; and from the bigger JPG, 10.145MB with the slider at 100% and 0%.

Whereas, JPGs in RGB, and PNGs, TIFFs, and EPS images in RGB and CMYK respond to compression proportionately when making PDFs (PDF/X-3).

I am attaching the two CMYK JPGs.

Walton

[Wosven]

There's no problem in the Beta 1.10.2.1187

[waltonmendelson]

Thanks for the suggestion.  But . . . I:

1. installed the Beta version of Publisher (1.10.2.1187)
2. placed the CMYK JPG into an 8.5 X 11 blank page
3. exported to PDF/X-3
4. set compression to 100 . . . 10.145MB

I repeated 3 & 4:

1. exported to PDF/X3
2. set compression to 0 . . . 10.145MB

I recorded this.  On my system, Window 10, Publisher Beta 1.10.2.1187 . . . CMYK JPG compression exporting to PDF/X-3 does not work.

Am I doing something wrong? Please note, I can compress RGB JPGs, RGB PNGs, RGB & CMYK Tiffs, RGB & CMYK EPSs.  It is only CMYK JPGs that do not compress.  

Are you on Mac?  If we used the same version of Publisher and the same images, that is the only difference.

Walton

[Dan C]

Hi @waltonmendelson,

Thanks for your report and screen recording/information provided, this is certainly helpful!

I can confirm I've been able to replicate this issue here and I have therefore logged it with our developers to be fixed.

I hope this helps

[waltonmendelson]

Thank you!

Although I discovered this running tests regarding file formats, color space, and compression as they might effect conversion to PDF--all of which regarding using Kindle Direct Publishing--I doubt this is, at a practical level, a big problem.  

Walton

[Dan C]

I've been speaking with our QA team regarding this and I believe we have found the cause for this file not being downsized!

I can confirm that this isn't due to the file being a CMYK JPEG, but it's actually caused by your Export settings.

Currently, the default setting when selecting PDF/X-3 is to 'Downsample images' when they're above 375DPI.

As this image is placed at 300DPI in your document, it isn't being downsized upon export, and therefore does not have JPEG compression applied either.

If you reduce this setting down to 299DPI (or any lower value to suit) then you will find that the JPEG Compression slider now works as expected, and will change the size of the exported PDF.

I hope this clears things up!

[waltonmendelson]

Your fix ain't a fix.

1) If the issue were unrelated to the CMYK, but rather to the Raster DPI setting of 300DPI, then that does not explain being able to compress PDF/X-3 file using RGB JPG, RGB PNG, RGB & CMYK TIFF, and RGB & CMYK EPS files all using the 300dpi setting.  However:

2) I changed the setting to 299DPI and the the PDF/X-3 file is 10.145 MB at 92% Compression which is identical to 100% compression.

3) I set the the Raster DPI setting to 299, set the compression to 0 and the PDF is 10.145dpi. I've attached a video.

4) The issue of exporting to PDF efficiently and accurately using Affinity Publisher is important: without being able to create good PDFs there is no reason to use Affinity Publisher. 

• In another post, I documented PDF file sizes varying over 100MB from time to time, with virtually no content changes.  That suggests some kind of problem.  
• Here I cannot reduce the PDF file size using compression, despite your "If you reduce this setting down to 299DPI (or any lower value to suit). . ."

As per your instructions I tried 299dpi, 298dpi, and 297dpi. All of the PDF/X3 files are 10.145MB at 0%, same as 100%!

Please understand: I am running tests to make recommendations as to how to set up using various programs, image file formats, etc. for people printing through Kindle Direct Publishing.  KDP guidelines set the image resolution to 300dpi.  I do not know what their lower limit is.  They did not used to have one, but they do now.  I am not sure I can say use 300 dpi resolution for you images unless you are using Affinity Publisher, then set things to ______. 

I have no problem with there being bugs in the programs, things happen.  I understand that.  But answers should make sense and they should be tested.  

 

[waltonmendelson]

I see that 1.10.3 is out.  I will download it and see what happens.

Walton

[waltonmendelson]

Let me show you the problem relative to the answer you were given by your QA Team.

Using the new Affinity Publisher 1.10.3.1191, and I've added "RGB" and "CMYK" to each test image respectively.  

Using Export to PDF/X-3 at Raster DPI: 300

RGB at    100% 4.357MB

RGB at      92% 1.486MB

CMYK at 100% 9.976MB

CMYK at  92%  9.976MB

If the DPI had to be reduced to 299 or lower, then the RGB JPG at 92% compression should not have been smaller.  The difference between these images is the the color space. 

Walton

 

[Dan C]

Thanks for the further information and images provided @waltonmendelson, but it appears as though you may have misunderstood my previous post.

You don't need to change the Raster DPI when exporting, the setting you need to change is Downsample images Above DPI - to below 300. Currently this is 375 by default when selecting the PDF/X-3 preset.

Please see my below screen recording, where you can see the exported PDF file size change after I've changed the above setting and then adjust the Quality slider -

I hope this clears things up

[waltonmendelson]

First: the QA answer ignores that keeping "Downsample images above DPI:" at 375 is the problem is exactly how I converted RGB JPG, PNG, RGB & CMYK TIFF, and RGB & CMYK EPS files to "Allow JPEG compression: Quality 92" to produce files that were significantly smaller.

92% is not a random number.  Affinity Publisher produces PDFs, in this test with these images, that hover around 4.3MB and 4.5MB for Photoshop is around compared to Adobe PDF Maker at 1.5MB and InDesign at 1.3MB.  Why?  Using Adobe's 0-12 scale (your 0% - 100%), #11/92% brings both AffinityPublisher and Photoshop significantly close to the lower file sizes.

File size is important because most print-on-demand printers have limits to how big file can be, above which they will not accept projects.

Second: Your setting on my system did not work. I will show you with screen capture. Here are two examples:

1. CMYK set to Downsample images above 299 and Allow JPEG Compression: Quality 92% . . . 92% is 9.976 and 100% is 9.976MB.
2. RGB set to Downsample images above 375 and Allow JPEG Compression: Quality 92% . . .92% is 1.486MB and 100% is 4.357MB

In these two examples--could something else be an issue, I don't know, these are the variables I set for these tests--the difference is Color Space, not the downsampling setting.

I will put all of this in a PDF an upload it later.  This may be more helpful with focused, individual screen captures, because the QA people don't seem to understand the problem.

Third: there is a problem with file size and PDFs made in Affinity Publisher, as one of my other posts demonstrate.  A difference of 50-100MB in a file is big! I have no idea is it effects printing.  I did try using the bigger 100+MB files on over a dozen books with no apparent ill effects: except that it pushed me too close to the maximum permitted file size. 

Walton

 

[Dan C]

Thanks for the further recordings provided - as I'm not seeing the same behaviour as yourself with the images provided thus far, I'd like to request a copy of your .afpub files shown in these screen recordings so I can test with your files directly.

Can you please upload these to the below link for me, then let me know once they've been uploaded?

https://www.dropbox.com/request/gEgeaLKabSqhjoQngaAk

Many thanks once again!

[Old Bruce]

I converted one of the jpegs to a TIFF 8 bits.

There is a problem with the CMYK JPEG image not being compressed. I am thinking this is because the Publisher Document is already a CMYK document and the JPEG image is already a JPEG in CMYK so what is there to be compressed? Is Publisher passing over the CMYK JPEG because that is already compressed, or is there some problem with Publisher and CMYK JPEGs?

As an aside I have to say that I find the use of CMYK JPEGs to be ... well ... an odd choice. One I would not make, one I would discourage when working with print.

[Wosven]

There's no problem with compressing file if you don't forget:

• to allow compression
• that it'll compress only images above set  PPI

 

Tests quality 0: notice the quality is equal in each image. Compression is done even with 300 PPI image (middle one)

Test quality 85%: no difference visible between images

Test quality 100%: all images seem with the same quality (no compression)

 

 

Same test with images already at 85% quality:

 

 

Now, the variation of files' sizes:

 

Images will be compressed depending of the quality in the settings, if they are above, at or below 300 PPI.

What annoy me is that they are compressed when at 300 PPI... or below. Only the ones at 399 should be compressed.

[waltonmendelson]

@Dan C

I have uploaded:

1. A PDF showing individual screen shots of for both the RGB and CMYK JPG conversions at 92% compression
2. My Affinity Pubishing file from the newest AffinityPublisher, 1.10.3. On  my screen the AfPub icon says Beta, but it is ver 1.10.3.

Thank you for the time!

Walton

[waltonmendelson]

@ Old Bruce

Thank you for the input. 

In terms of PDF file size, it may be more effective to apply compression in the conversion process itself, rather than to the source images. At any rate, that was what I was testing. This compression worked in Affinity Publisher for RGB JPG, PNG, RGB & CMYK TIFF, and RGB & CMYK EPS.  It only failed with CMYK JPG.  All settings were the same for each test.

As for why anyone would use CMYK JPG, that actually is easy:

My tests are aimed at the KDP (Kindle Direct Publishing) world.

Most non-professionals work in RGB (in fact don't know what color space they work in, but sRGB is the universal consumer color space). If they convert their work to PDF/X-1a or PressQuality, RGB will be converted to CMYK. And most people, again, won't compare the original RBG to the new CMYK, and will simply upload the files for printing. Not all RGB to CMYK conversions are successful.  

KDP uses non-traditional process colors (compared to Pantone CMYK process colors).  They have a significantly large CMYK gamut than most commercial printers.

If one is going to produce a PDF in CMYK, I would argue the work should be converted to CMYK and compared to the RGB originals in a graphics program, where color correction and/TOC corrections can be made. Then the question is what file format to save in.  JPGs make perfect sense, and if they would be in CMYK.

Am I making sense?

Walton

 

 

 

[waltonmendelson]

@ Wosven

Thank you for the testing.  I'm a bit confused, because while your settings are different, mine worked exactly as they should for RGB JPG, PNG, RGB & CMYK TIFF, and RGB & CMYK EPS images.  Why would I need to change settings because a JPG is in CMYK?

I have sent my two test images and the Affinity Publisher file to Dan C, so we'll see what's up.  It is always possible that my Windows 10 system is doing something, or maybe I am inadvertently. 

Again, thank you!

Walton

[Old Bruce]

2 hours ago, waltonmendelson said:

As for why anyone would use CMYK JPG, that actually is easy:

I am not questioning the CMYK but I am questioning the JPG. I just think of JPEG and PNG as RGB file formats, TIFF is either RGB or CMYK. I guess it is down to the JPEG artifacts being worse to my eye with CMYK.

[waltonmendelson]

@ Old Bruce . . . 

Many years ago, back in the Photoshop 3 days or earlier, I believed TIFF was the only way to go.  JPG compression was a priori bad.  Period.  

I have done tens of thousands of test relating to file format, compression, color space, dpi (especially for fine line art like engravings), printability (commercial and home), etc. 

I assume that most of us work in the native file format, opening, saving, closing.  But afterwards?  I have working files that approach 2GB.  Beyond that, I prefer the light weight of JPGs.  

The attached image, is a snapshot, if memory serves me, the small details (from 5X - 20X) are 300%.  Somewhere, I have the same details as scans from a printed (halftone) piece. The image degradation after 100 open/save/close cycles is invisible, and if you know where to look, it is de minimis.   

I've run similar tests with high quality images.  After 60 open/save/close cycles, and at 300-600%, I couldn't find any degradation.   

If your workflow works for you, do not change it.  But most people's fear of JPGs is misplaced.  In fact although there are options, the default compression in PDFs is JPG.  

In these tests I'm running now, I cannot see any difference between the test image saved at JPG 85% (0.7MB) and TIFF (33.6MB)

Of course PNG is RGB and was never intended or designed for anything other than web use. 

Walton

 

 

 

[Dan C]

Apologies for the delayed response here, as this has begun a much larger discussion regarding compression and when this should be applied when exporting to PDF.

I can confirm that a bug has been logged with our developers and we're hoping to resolve this in a future update.

I hope this helps

[waltonmendelson]

@ Dan C

Thank you!  

Although I noticed this problem, and inasmuch as it seems to only effect CMYK JPGs, I believe that it would be an extremely rare problem, bordering on "never."  Kindle Direct Publishing and other p-o-d printers, have maximum file sizes, but I've never worked with a traditional commercial printer who did, so reducing the file size would be rare, outside the p-o-d world.  Most people work in RGB, if they even know what color space is. And, most people who want to submit work in CMYK, generally export to PDF/X-1a.  In other words, most people would never create a CMYK JPG, let alone want to reduce its file size.

However, in terms of file size, my few tests suggest that a much bigger reduction in size will be gained through compression when exporting to PDF, than compressing the source images.  Could be wrong here.  But that's what I've observed. 

Again, thank you for looking into this.

Walton