Why does Publisher v2 create such large PDF files?

[Robocat]

Publisher creates really large PDF files, up to three times larger file sizes than InDesign.

That is, a similar document with one large image, 300 dpi, LZW, RGB, 100 JPG compression: InDesign 1 Mb (Acrobat 5 or 8/9) and Publisher 3.4 Mb (Acrobat 8).

What could be the reason?

Publisher's PDF files sometimes have to be further compressed in Acrobat Pro 🤔

[thomaso]

12 hours ago, Robocat said:

one large image, 300 dpi, LZW, RGB, 100 JPG compression: (…) What could be the reason?

Your combination of "LZW" + "JPG compression" appears unclear. One reason might be that Affinity did not resample or recompress, regardless of identical value settings. – Can you upload two sample PDFs for inspection / comparison?

[Alfred]

2 minutes ago, thomaso said:

Your combination of "LZW" + "JPG compression" appears unclear.

Agreed. LZW compression is lossless, JPG compression is not (even at ‘100%’ quality, or minimum compression).

LZW and ZIP compression yield similar file sizes for 8-bit TIFF files, but LZW compression can increase the file size for 16-bit TIFF files (so ZIP is preferable).

[thomaso]

Apart from to bit depths also profile embedding (vs. image conversion) may matter, especially if you compare the PDF file size with a few images only where the embedded profile(s) may be larger than the image size(s). Here an Affinity comparison with 1 tiff + 1 jpg but identical sRGB profile for images + document:

[Robocat]

Tested as follows:

Image: RGB TIFF, No LZW (8-bit): 39 Mb, LZW (8-bit): 32 Mb

InDesign: Image quality (JPEG) Max.

LZW ON = 3,3 Mb

LZW OFF = 3,3 Mb

Publisher: Image quality (JPEG) 100

LZW ON = 13 Mb

LZW OFF = 13 Mb

JPG image quality 87 (no LZW) = 3 Mb 

[thomaso]

What is "JP" ? – I might be wrong but I vaguely remember that ID maximum quality exports with 98%, not 100%. – Again, can you upload two exported PDF (ID / APub) for a closer look?

[Robocat]

As I wrote, the size of Publisher's PDF is 13 MB, so I can't upload because the forum's maximum file size is 2 MB. But whatever you compress, etc., InDesign makes about 15-75% smaller PDF files (in this comparison).. it's a fact. 🙂

a few percent difference in image quality (compression) does not explain such a big difference.

LZW Pub.pdf LZW ID.pdf

[thomaso]

2 hours ago, Robocat said:

a few percent difference in image quality (compression) does not explain such a big difference.

This maybe a misunderstanding. Especially with high quality / low compression the file size differs massively with a little change of compression. Have a look at this website with interactive comparisons of various motives, compression rates and resulting file sizes. Though it is for Lightroom it may explain the principle of the non-linear change of file size though Affinity may use different methods / algorithms for resampling or compression.

Accordingly a comparison of your image, extracted from the apub.PDF + exported at different qualities (100%, 98%, 95%, …, 70%) influence the resulting file sizes quite differently: At the high end, 10% less quality results in a 50% smaller file size.

Also the Exiftool reports a different compression / quality estimation for the two JPG files after extracting them from their PDFs. While it is an estimation only it obviously notices a quality difference in this two files of same motive and nearly same megapixels:

And regarding subsampling Exiftool reports different methods for ID/APub:
ID:      YCbCr4:2:0 (2 2)
APub: YCbCr4:4:4 (1 1)

Comparing the PDF data in Acrobat it appears the different file size is caused by the image with 99% of the file size, which again seems to indicate different qualities / compression rates:

 

3 hours ago, Robocat said:

forum's maximum file size is 2 MB

I am not aware of such a low limit for single files, if their is any it is far above 2 MB. Possibly it is related to the number of posts you did in the forum. For certain file types (.e.g. JPG) it also may help to upload them as ZIP to prevent the forums / server software to do any changes (e.g. recompress, strip profiles).

[Robocat]

(Link does not work, 404.)

The same one-page document (big tree). Simplified (you don't change the settings); if you want a Press Quality PDF (CMYK) file in InDesign, you choose the Press Quality preset. Same selection in Publisher (press ready). Publisher exports a 9 Mb file and InDesign 8 Mb (rounded).

If InDesign's "maximum" image quality is 100(?) and Publisher's is 98, i.e. lower, why are Publisher's PDFs bigger? It doesn't matter in Prepress.. but...

Another surprising thing is that if you import the image into Publisher and don't change its size (100%), everything is as it should be. But if you change the size, for example, to a smaller one, then Publisher will increase the resolution of the image (dpi). What is the cause and why does InDesing not do the same? That's why I import the image at 100 percent and reduce or enlarge it to the size I want. Then in Photoshop I resize the image to match the final size of the image in Publisher. If it's pointless, tell me 😁

[walt.farrell]

17 minutes ago, Robocat said:

But if you change the size, for example, to a smaller one, then Publisher will increase the resolution of the image (dpi). What is the cause

When you Place an image you get all its pixels, and if you place it at 100% of its original size the DPI will match the original image.

If you Place it at a smaller size (for example, 50% of the original size) you still have all the pixels, but they are squeezed into a smaller space. Logically, therefore, the DPI must increase. When you Export the file as a PDF, you can specify in the Export Options whether such images should be down-sampled, and in what way:

[Robocat]

(Same big tree -image)

Okay, but if you reduce the image (50 %)(570 dpi) in Publisher and don't use Downsample, the PDF size is 33 Mb 🤨 . If the image has not been resized and Downsample is off, the size of the PDF is 9 Mb. Not good.

I've been taught that if you're going to enlarge or reduce an image by -20/+120 % of the original, do it in Photoshop.

If the dpi is more than 300, then it is of no use (except for drawings), it is unnecessary "weight".

[Robocat]

41 minutes ago, walt.farrell said:

When you Place an image you get all its pixels, and if you place it at 100% of its original size the DPI will match the original image.

If you Place it at a smaller size (for example, 50% of the original size) you still have all the pixels, but they are squeezed into a smaller space. Logically, therefore, the DPI must increase. When you Export the file as a PDF, you can specify in the Export Options whether such images should be down-sampled, and in what way:

Oh, yes of course! I forgot that Downsample limits the dpi when exporting. So, I don't need to go to Photoshop to resize the image.  😁

Thanks!

[thomaso]

3 hours ago, Robocat said:

(Link does not work, 404.)

Which one? To me both links work from this and another device without issues.

2 hours ago, Robocat said:

The same one-page document (big tree). Simplified (you don't change the settings); if you want a Press Quality PDF (CMYK) file in InDesign, you choose the Press Quality preset. Same selection in Publisher (press ready). Publisher exports a 9 Mb file and InDesign 8 Mb (rounded).

I think we can't simply compare the "Press Quality" / "press ready" presets of the two different applications. We would need to consider not only the exact compression rate but also colour / profile handling, which may influence the rather small difference of ~10% in your example of 9 vs. 8 MB.

2 hours ago, Robocat said:

If InDesign's "maximum" image quality is 100(?) and Publisher's is 98, i.e. lower, why are Publisher's PDFs bigger?

As mentioned, I am not sure if ID's "maximum" exports indeed with 100% quality, though I don't know what compression rate gets in fact used. Since the compression % is quite relevant especially for high quality (100 – 90%) we need to know & consider the actual compression rate for a useful comparison.

[Robocat]

7 hours ago, thomaso said:

Which one? To me both links work from this and another device without issues.

https://regex.info/blog/lightroom-goodies/jpeg-quality

[thomaso]

@Robocat, the link to this page and site doesn't start with "https://", it seems your browser adds the "s" which you might remove manually.

[Robocat]

26 minutes ago, thomaso said:

@Robocat, the link to this page and site doesn't start with "https://", it seems your browser adds the "s" which you might remove manually.

Yep, now it works

[Alfred]

17 hours ago, thomaso said:

interactive comparisons of various motives, compression rates and resulting file sizes

A motive is an impulse that incites someone to do something. Do you perhaps mean patterns?

[thomaso]

@Alfred, thanks for pointing this out. I mean various topics/objects/subjects in images, so it might be "motifs" – rather than "patterns" which sound to me to be limited to regular, geometrical and repeated content in a images. (in German the two meanings of "motif/ve" use the same -ve ending)

[Oufti]

16 hours ago, thomaso said:

(in German the two meanings of "motif/ve" use the same -ve ending)

And in French, the two meanings are rendered by the form motif…