Monchrome images in exported PDF seems like CMYK?

[mariog69599891]

It seems like InDesign is reformatting my images when I don't want it to, during PDF export.

I have a simple InDesign document.  I place an 8-bit grayscale TIF file, and a monochrome (B&W) TIF file on a single page.

I export this to a [PDF/X-1a:2001] file, with the following change:

     Output - Color - Color Conversion = No Color Conversion

I then open the exported file with Acrobat DC, and select Tools / Export / Image / TIFF ( Export All Images )

Using Photoshop CC, I open the two TIF files that were exported.

The 8-bit grayscale image is still an 8-bit grayscale image.

However, the monochrome image is now a CMYK image.

Since InDesign's Export feature specifically contains Compression options for Monochrome images, why am I getting a CMYK in exported out of the generated PDF file?

Or most importantly, how can I export my InDesign file so that I'm sure the monochrome image remains monochrome (1-bit B&W) in the PDF it creates?

Thanks in advance

[BobLevine]

Why are you using X/1-a?

Use X/4 and don’t change anything.

[mariog69599891]

Thanks, but I am using it because the client specified it as a requirement.  I can ask them to change it, but I would only do so after I can confirm that the same thing doesn't happen in that format.

[rob day]

I export this to a [PDF/X-1a:2001] file, with the following change:

     Output - Color - Color Conversion = No Color Conversion....

Thanks, but I am using it because the client specified it as a requirement.

If you set the Color Conversion to No Color Conversion the PDF is no longer a PDF/X-1a—the Standard dropdown will change to None. If your client really needs PDF/X-1a you have to set the Color Conversion to CMYK, which is an X-1a requirement.

[mariog69599891]

Thanks to everyone for your responses, I appreciate it.

For additional background, my PDFs were sent to a printer who responded that I was using "zip compression on 1 bit spot color monotone images".  I took the 'spot color' to mean that I was using some color other than 'K'.  Also, I set InDesign to ZIP compress Color and Grayscale images, but CCITT for monochrome.  His statement lead me to review my files by exporting them from Acrobat and finding that one remained grayscale and the other was converted to CMYK (acknowledging now the Acrobat PDF may be an issue).

I did as Danny suggested, and in the preview neither of the two images reports anything but a 'K' value, with C,M, and Y all zero.

Vinny, I am positive that the images are not changed.  I took my 2 images, verified in Photoshop they were 'Bitmap' and 'Gray', then closed without saving.  Created an InDesign document, placed them, and output the PDF, following my original steps, and the same event.

Derek, it is for commercial printing, but I'm afraid I don't know much more about the final target as I am something of a middleman.  By "monochrome" I mean a 1-bit per pixel B&W image that does show as "Bitmap" in Photoshop.  But I chose the term 'monochrome' because that's what InDesign uses in it's Export PDF / Compression settings (unless I'm missing something else).

So maybe it's not an InDesign question but a simpler one for PDF.  As Danny pointed out the Print Production tool looks very helpful.  But, is there any way on a PDF that I verify things about images in a PDF such as bit-depth, color profile, compression, and whether it's bitmap/grayscale/color?

[rob day]

printer who responded that I was using "zip compression on 1 bit spot color monotone images".  I took the 'spot color' to mean that I was using some color other than 'K'.

No, it means you've assigned a spot color (PANTONE Solid swatch?) to the 1-bit image. If the job is process CMYK you shouldn't be using spot colors.

Open Acrobat's Output Preview—spot colors will be listed as extra plates below the CMYK plates.

[rob day]

But, is there any way on a PDF that I verify things about images in a PDF such as bit-depth, color profile, compression, and whether it's bitmap/grayscale/color?

Yes Object Inspector. See my #6. Sometimes Object inspector can be fussy about where you click. If it is, zoom in and click on a colored pixel—sometimes I have to click more than once.

[mariog69599891]

Rob, thanks for all your helpful and informative replies.

No, it means you've assigned a spot color (PANTONE Solid swatch?) to the 1-bit image.

I don't believe I've done that.  With InDesign, I created a new document, Place the 1-bit image on a page, Place the grayscale image, and then Export it.  And when I look at it in Acrobat Output Preview, it doesn't show any extra colors in 'Seperations', just C,M,Y, and K.

So I'm not sure why the printer mentioned "1-bit spot color monotone images", if all that shows in Print Production - Output Preview.

When you place a 1-bit image the monochrome pixels always get assigned a color, which is by default the CMYK [Black] swatch. If you direct select the image you can assign any CMYK, RGB, Lab, or Spot color.

Does this explain why I am getting a 4-bit image in my PDF when I started with a 1-bit image? I reset everything back to PDF/X1a defaults and did an export of just the 1-bit image, and the OutputPreview in Acrobat shows it as a 4-bit image.  If I use Acrobat DC to create a new PDF file, then place the same monochrome TIF file in it and save it as PDF/X1a, when I inspect that PDF file it contains a 1-bit image.

If it helps, I have created a demo InDesign file and Acrobat DC-created PDF file, and the results of both exporting:

Dropbox - BitmapPDFOutput.zip

Thanks again for all this help.

[rob day]

I don't see a problem with any of the PDFs. in all cases the bitmap or grayscale image would output to the CMYK black plate.

Can you post the PDF that you submitted to the printer?

[rob day]

Also, the bits per pixel is not relevant in your case because there are no gray levels (other than black and white) in your placed image. InDesign lets you assign different colors to the white and black pixels, but you've left the image at the default [Black]. With an PDF/X-1a export the black pixels have no where to go other than the Black plate, which all of your PDF's are showing.

You could assign different colors on purpose or accidentally, that's why it would be helpful to see the PDF the printer is rejecting, or at least a capture of the Swatches panel of the job's InDesign document.

These wouldn't cause a preflight problem:

But this would:

[mariog69599891]

Rob, thanks again for all the help.  Hopefully I can repay it one day to you or pass it forward to someone else.

I'm afraid I can't give out the PDF as it's not my material to distribute and it is copyrighted.  But I am confident my examples were created in the same manner.

What I still find odd is how the printer indicated "1 bit spot color monotone images" when the images do not appear as a spot color (I expected), or even 1-bit monotone (I expected, but my PDFs indicate 4-bit).

In any case, you and the others have given me a wealth of information, and I appreciate it.  I think I have enough information to give it another run and respond to the printer with intelligent information if I hear back from them.

[rob day]

What I still find odd is how the printer indicated "1 bit spot color monotone images" when the images do not appear as a spot color (I expected), or even 1-bit monotone (I expected, but my PDFs indicate 4-bit).

I think the extra bits coming out of InDesign are there so the image can act as a mask and have any color applied, which is an important ID feature, but doesn't affect output quality. The printer might also be flagging the resolution of your 1-bit images—typically 1-bit images filled with black (line art) need more resolution. The line art with text in your example would need 1000+ ppi to be accurately resolved.

[Danny Whitehead.]

I'm not sure I'd trust an image exported from Acrobat as evidence of a conversion happening in InDesign's PDF export.

In Acrobat, bring up Output Preview (Print Production > Output Preview). Hover over the image. Does it show anything on the C, M or Y separations?

[vinny38]

+1 for both answers above.

First, I would definitely check PDF using Acrobat Output Preview.

Now, is there any chance you applied a color to your bitmap image?

See example below: I "accidentally" selected the image using direct selection tool and applied "Registration".

Looks black but obviously if I check my PDF, my black is in fact 100/100/100/100...

You might want to check that too...

[Derek Cross]

Are you trying to produce a PDF for commercial litho printing? If so, follow Bob's advice.

By  "monochrome" do you mean bitmap?

[rob day]

Or most importantly, how can I export my InDesign file so that I'm sure the monochrome image remains monochrome (1-bit B&W) in the PDF it creates?

When you place a 1-bit image the monochrome pixels always get assigned a color, which is by default the CMYK [Black] swatch. If you direct select the image you can assign any CMYK, RGB, Lab, or Spot color.

If you export the page with No Color Conversion Acrobat defines the 1-bit image as an ImageMask filled with whatever Color Space and Color Values you chose over in ID. You can use AcrobatPro's Output Preview>Preview>Object Inspector to see the image info. The Separation preview only tells you how the image's color will output given the chosen Simulation profile, and not anything about the image itself.

Here the selected 1-bit image is filled with a Pantone Color:

And here's the same image with a 100|0|100|0 CMYK fill