InDesign question: Applying basic feather to photo alters appearance

[hoosker]

I never noticed this before. In a CS4 InDesign document (CMYK transparency blend space) when I apply a basic feather to a greyscale photo the photo becomes noticeably lighter. This washed out effect is very undesirable. When I export a high quality PDF the photos also look muted. I have not noticed this with RGB photos.

Does anyone have a suggestion on how to avoid this? I searched the web for an explanation without any luck. Thanks.

 

[spacemanspifff]

Image colourspace

If you are using the CMYK colourspace then all of your images should be in this colourspace too. If you don't plan on printing your files in CMYK then you can leave the images in RGB, just make sure you do not allow the pdf export to change the colours.

Otherwise, using Photoshop or some other image editor, check that your grayscale image is in fact grayscale and not RGB and also check that any colour images are CMYK not RGB before you place them in InDesign. You will be able to see any undesirable changes in photoshop when you change the mode and possibly correct them.

From what you have written, I believe that what you are seeing is due to the images being changed to CMYK from RGB when you make your PDF. You should find that this change happens (maybe to a lesser extent) even if you don't use the basic feather.

Hope this helps....

 

[hoosker]

Thanks, spacemanspifff

This is a magazine that all pages will be off-set printed in black ink only except for the cover which has a duotone (black and 1 pms) saved as eps. But the images in question are photoshop greyscale.

I read something in an Adobe forum after I posted this that may explain what I am seeing. If I understand correctly, InDesign does not preview the grey scale correctly until you add transparency which in this case is a feather. It then is forced to preview the greyscale image as it would look only using the black plate. This in comparison to a cmyk black and white photo which would be printed as rich black using some of the color plates too. So I am seeing a more muted black ink only image.

What is interesting is that when I export a high quality PDF it shows the same phenomena. The greyscale image with the feather looks more muted. Actually all images on the page become muted even if only one has the feather. If I export a high quality PDF with no feather the images are darker.

Then I did the same thing but exported a press quality and all images look more muted whether I used a feather or not. So maybe it is the black plate only vs rich black that I am seeing.

 

[spacemanspifff]

Appearance of Black

If you look in your Indesign Preferences you'll see some settings for appearance of Black - These settings only change what you see on screen, not what will be printed or rendered in the pdf.

When you have add photograph with Feather (as you know) this adds transparency to the file, which means that when you export the job out to pdf or try to print it may require flattening.

The shift in colour could be due to your settings in your pdf export. When you choose high quality it might be using an RGB CMS profile to create the pdf which would lead the images to look blacker. When you choose press quality it could use a CMYK profile which will make the images look grey.

I would look at these settings first. Of course all of this is only a guide as the final printed output will depend on how much ink the printer puts on the press and how absorbent the paper stock you're printing on is.