For the new Adobe InDesign export settings V2.5 for PDF/X-4 CMYK+RGB from PDFX-ready the technical committee of PDFX-ready has investigated if a change of the compression method from the traditional JPEG to the newer JPEG2000 would be useful.
JPEG2000 uses a completely different compression technology (wavelet transformation) than the old JPEG (discrete cosine transformation). The new technology promises a better quality together with smaller file sizes. JPEG2000 also allows images with more than 8 bits per channel and up to 256 channels. That sounds promising…
We already knew from tests of the Ghent Workgroup that not all PDF viewers (especially on mobile devices) can handle PDFs with JPEG2000. With other PDF viewers (including Acrobat/Reader) displaying JPEG2000 images is much slower than JPEG images.
But after all we wanted to know if we could recommend JPEG2000 compression for prepress data. That’s why we decided to perform a series of practical tests with a calendar with highres images in different color spaces (Device-CMYK, ICC-CMYK, ICC-RGB). Peter Kleinheider has done the output tests with two different RIPs and I did the export tests with Adobe InDesign CC2017.
When comparing the test results we noticed some unexpected surprises!
Bug in Adobe InDesign
Already in Adobe InDesign CS 5.5 I had discovered a buggy export setting for PDF/X-4 with JPEG2000 maximum quality. While for all other JPEG2000 compression qualities the file sizes are slightly smaller than for the corresponding JPEG settings (as expected), using maximum quality results in a much bigger PDF which has exactly the same file size than the export for lossless compression quality:
This behaviour has been reported multiple times to Adobe but the wrong setting is still part of the lastest version InDesign CC2017. For JPEG PDFX-ready is recommending maximum quality. But when using maximum quality for JPEG2000 the InDesign users get punished with much bigger file sizes.
The InDesign PDF export using maximum qualitiy for JPEG2000 leads to unnecessary big files sizes and is therefore not recommended!
That’s why we have decided to use high quality for the JPEG2000 samples in our comparison test. (BTW: high quality JPEG2000 delivers better quality than maximum quality JPEG!)
Four use cases (workflows) have been tested:
- Device CMYK images already converted in PhotoShop (early binding)
- Device CMYK images converted during PDF export (intermediate binding)
- CMYK images with embedded ICC profiles (color managed workflow)
- RGB images with embedded ICC profiles (late binding)
For all of the four variants a PDF was exported using JPEG with maximum quality and an other using JPEG2000 with high quality.
Comparison of PDF file sizes
As expected the PDF files containing JPEG2000 compressed images are significantly smaller; except for CMYK images with embedded ICC profile!
Comparison of export times
PDF export using JPEG2000 takes much longer than JPEG export.
The PDFs created during our export tests were processed on two modern RIPs (same hardware) utilizing standard settings:
Ripping PDFs with JPEG2000 compression takes much longer.
This was confirmed by users who were running into problems ripping with JPEG2000 files.
Using JPEG2000 compression for prepress files with the current implementations has huge disadvantages. A small reduction of the file sizes must be paid with a massive increase of export and output times!
Consequently PDFX-ready has decided to not introduce JPEG2000 compression at the moment.
Please share your experience with JPEG2000 in the Comment section below.