View Issue Details
|ID||Project||Category||View Status||Date Submitted||Last Update|
|0016072||Scribus||public||2020-03-25 19:15||2020-03-28 14:01|
|Status||closed||Resolution||no change required|
|Target Version||Fixed in Version|
|Summary||0016072: Black is not black for graylevel images in pdf export|
|Description||Hello and thanks in advance,|
I build La Revue russe now for 8 n° (4 years).
We send a big pdf file in 600 dpi with gray level pictures inside.
I found pictures "a little gray" after printing by Imprimerie Paillard in France. When Scribus opened the pdf file I looks a little gray only for the pictures. I got a screen sensor to calibrate my screen Samsung.
I was not sure, now I am.
I will send pdf test files with Acrobat 4, 5 and 6 and the Scribus one.
After months It seems that the problem is coming from File Compatibility> PDF 1.3 (Acrobat 4).
Many thanks and best regards,
|Steps To Reproduce||Open RR53 test images.sla try to export in pdf, 600dppi no compression ... take care with Profil actuel : PDF 1.3 according to file option Compatibility PDF 1.3 (Acrobat 4).|
Test with 1.4 (Acrobat 4) and 1.5 (Acrobat 6)
|Additional Information||Look at my file RR53 test images Ac4 is good. |
Ac5 and Ac6 are bad.
Files are here :
|Tags||black, color management, gray, pdf export|
||The .sla document does not embed images. Please provide images used by your sample document.|
Nice to read you once more,
At the end I test pdf black level in GIMP :
In "barre de controle" out of page on the left I find : 35 (in all Ac4, 5 or 6)
In the Scribus one made by hand "0".
Lien du new Smash
Trofimov - page 1
Trofifimov.tif - page 2 up
Trofifimov.bmp - page 2 down
Trofifimov.png - page 3
and a sla with images incorporated (never done before)
||I already had a look at the RR53 test_image_Ac4/Ac5/Ac6.pdf fields you provided. For your information, the data for the exported images in the three PDFs are strictly identical. Adobe Reader does not show any difference either when displaying the three PDFs on screen.|
I did several tests by making a sample test file with entirely black images and exported this file to PDF 1.3/1.4/1.5 using grayscale. The exported value for the image black was in all cases and as expected 0. So if you see 35 in GIMP, that means GIMP has probably applied some kind of color management when importing the PDF. As I have already said it plenty of time, GIMP is not a valid tool to inspect PDFs.
One thing to know: when printing in grayscale on press, the black ink alone does not allow to produce blacks as black as what CMYK can produce when using all 4 inks. In fact if you print a large square using K ink only with standard ink density values, it will look as a dark grey and not really black. That's why high end B&W photography books are regularly printed with more than just black ink. I've seen such books printed with Black + Pantone and even full CMYK.
I use Adobe Reader 9 ver 188.8.131.52
I send Sreencapture with pdf AC4 left and Ac6 right opened in Adobe reader on my screen. Hope you see a difference.
Ac4-Ac6.png (887,324 bytes)
Ac4-Ac6.png (887,324 bytes)
GIMP is not a valid tool to inspect PDFs.
Please tell me a valid one ?
I see a difference in your screenshot. It looks like you have the transparency blending space defined as CMYK in Adobe Reader display preferences. This has following consequence:
- PDF 1.3 does not support transparency, so in PDF 1.3 files, this setting will make no differences and grayscale images will continue to be displayed as if they were RGB unless you activate also overprint preview
- PDF >= 1.4 support transparency, so for these files, setting the transparency blending space to CMYK will also have the effect to display grayscale images as if they would be printed using black ink only.
If you force overprint preview in Adobe Reader preferences, both Ac4.pdf and Ac6.pdf will look as what you observe on the right part of your screenshot. When overprint preview is enabled, Adobe Acrobat/Reader will perform a CMYK on screen simulation and will display grayscale images as if they would be printed using black ink only. When overprint preview is disabled (and transparency blending space set to RGB for PDF >= 1.4), grayscale images are displayed by Adobe Reader as if they were RGB images. They look more vibrant, but this will not match the print result.
So no bug in Scribus, just a matter of display preferences in Adobe Reader.
>> Please tell me a valid one ?
Adobe Acrobat with Enfocus Pitstop.
||Or for PDF hackers podofobrowser or a simple text editor.|
|2020-03-25 19:15||r.brunet||New Issue|
|2020-03-25 19:15||r.brunet||Tag Attached: black|
|2020-03-25 19:15||r.brunet||Tag Attached: color management|
|2020-03-25 19:15||r.brunet||Tag Attached: gray|
|2020-03-25 19:15||r.brunet||Tag Attached: pdf export|
|2020-03-26 00:09||jghali||Note Added: 0047455|
|2020-03-26 10:57||r.brunet||Note Added: 0047464|
|2020-03-26 11:31||jghali||Note Added: 0047465|
|2020-03-26 13:38||jghali||Note Added: 0047469|
|2020-03-26 14:51||r.brunet||File Added: Ac4-Ac6.png|
|2020-03-26 14:51||r.brunet||Note Added: 0047471|
|2020-03-26 15:00||r.brunet||Note Added: 0047472|
|2020-03-26 15:32||jghali||Note Added: 0047473|
|2020-03-26 15:32||jghali||Note Added: 0047474|
|2020-03-26 15:33||jghali||Note Added: 0047475|
|2020-03-28 14:01||jghali||Assigned To||=> jghali|
|2020-03-28 14:01||jghali||Status||new => resolved|
|2020-03-28 14:01||jghali||Resolution||open => no change required|
|2020-03-28 14:01||jghali||Status||resolved => closed|