Acrobat Color Conversion= Lossy?

[mushmush]

Hello all- I've had an issue when using Acrobat to convert a Pdf file to a specific Profile.
The problem I've run into is that after the conversion (the images where Adobe 1998 RGB) the images now show significant Jpeg compression.
I don't have the source material- the original image files- just a 44 page Pdf.


I think I've seen this happen once before but it was a long time ago- never did figure it out and used a work around. The work around used is not suggested for 44 pages.
I can extract the images into Pshop one by one and convert :: they seem fine.

Anybody seen this?

[andrewrodney]

Check your preferences for Convert to PDF. It might be set for JPEG but you select TIFF, then select the Edit button and check the options.

[mushmush]

Thank You Sir- it still seems so be adding compression artifacts though.
I've tried it with both the Tif and the ZIP settings and both are still creating the artifacts.

I have read that it can be a by-product of the original Jpeg placed into the Pdf.
------It may be that if that Jpeg (if it was a Jpeg) was saved with a mid to low quality setting -that the conversion via Acrobat causes it to re-save the file under that same Jpeg quality setting & cause the artifacts -------------------


It's curious that I can extract the images using the Touch UP Object tool and adjust using P'shop and save with no gain in the artifacts.
My next step is to ask for InDesign file with the native image files- which isn't a huge issue but it undermines my confidence in the Acrobat conversion process.
Thanks again!

[plugsnpixels]

If I may ask a related question here:

Is it possible to resave a color PDF as a grayscale one in Acrobat Pro? I routinely save my own layouts as Optimized PDF but there are cases (such as with Google Books downloads) where one doesn't need the color images. If this is a matter of choosing an output profile as in the OP, I'm not sure how this is done.

Wait: this seems to be under Preflight, yes? Testing...

[andrewrodney]

Originally Posted by mushmush

I have read that it can be a by-product of the original Jpeg placed into the Pdf.

Absolutely! The damage was done with the original JPEG conversion.

[mushmush]

Yep= I need some native files

[chet webley]

Originally Posted by andrewrodney

Check your preferences for Convert to PDF. It might be set for JPEG but you select TIFF, then select the Edit button and check the options.

If you choose the right type of PDF to convert to, you can specify at what resolution the compression kicks in, what resolution the images then get resampled to, and by how much the images get compressed.

I've attached my favourite image compression settings

CompressionSettings.jpg

[mushmush]

HI Chet,
- thanks for the screen grab- I'm running Acrobat 9.5.1 and can't seem to find this Dialogue box.
I'll keep hunting, it maybe my version is a little older

[mushmush]

Oops- it's Acrobat Distiller= I'm a knucklehead

[Shoku]

The compression is caused by the export settings in the layout program. If the exported PDF is opened in Acrobat and converted to another color space (RGB to CMYK for example), Acrobat will use the embedded down sampling compression instructions and re-sample the jpeg again making it look even more jagged. The only way to prevent this is to set the Export settings in your layout program to use no compression when down sampling.