Topic awaiting preservation: PDF Amazement

I know pdf makes files alot smaller... but i really didnt expect this!

I have a 150 page catalog, which has roughly 2 gig of images linked to it. The images are all cmyk, from 300 to 600 dpi.

When i made the pdf, i converted all text to outlines and used the press quality setting in distiller. So 2400 dpi etc.

The final PDF size is an amazing 76mb!!!

How does it get it so small and keep the image quality, or is there something wrong with my pdf and it shouldnt be so small?

Hum... I know that in a PDF everything ( images, fonts ... ) is included but it seems like if the images are not embedded in the PDF or have been re-compressed brutally.
To make sure the images are effectively in the PDF, have you tried to open it on another computer, or rename the folder where the images were ?

The 2400 dpi, should have no impact on the file size of your PDF. Acrobat/Distiller won't expand your 300 or 600 dpi images to 2400 dpi just for fun, all the more that it has no way to re-create the new pixels.

You said you haven't noticed a loss of quality on the images, but what was their original file format ? If they were in raw TIFF, Acrobat/Distiller probably compressed them in JPG on the fly. If you ask me, I'd vote for that solution.

Hmm i will give it ago on another pc and see if it prints... the document doesnt say it has any externat links, and all the images have gone through the tranparency flattener so i wouldnt say they are linked.

Orignally the files were brought into photoshop at 600 dpi, where i gave them clipping paths and saved them as tiff's with transparency. The images are either 300, 400 or 600 dpi.

Is it a problem if distiller has compressed them in JPG on the fly? should i change a setting somewhere?

If Distiller compressed the picture, which is not sure yet, I don't see it as a problem as long as there's no noticeable loss of quality on them. And according to your first post, the pictures are still of good quality.

maybe your initial 2gigs of images are bitmaps and when compressed to any normal format like jpg, become a lot smaller, and thats what happened with your pdf? Because 2gigs of images is A LOT

Depending on your compression settting, the 600dpi image will be down sampled to 300dpi, and then jpeg compressed, open up distiller and take a look at the press compression defaults.

With 4-color or grayscale you will not suffer much allowing the image to be down res'ed to 300 dpi, as as most RIP would likely downsample the image to around that resolution if not told otherwise. But with bitmaps you my what to prevent this from accuring expecially bitmaps as they should be supplied at the RIP linework resolution. So they will print at the same quality as if the were produced as type or vector (Linework) elements.

As for jpeg if your print vendor give you an ok to supply pdf or postscipt files containing Jpeg compression it should be find to do so. Keep in mind if the file will need to be open and reencoded several times, you may experance jpeg artifacts. In our workflow we often edited the PDF directly changing pricing and shipping codes just prior to the files being shipped so we perfered not to compress. Also some older equipment which we had would allow us to image PDF files.


J. Stuart J.