InDesign, PDFs and re-sizing images ...

Question

I've just completed a photo book in InDesign and am ready to export it as a high-rez PDF and send it to the printer.
All of the original images are 300dpi.  The original images, where needed, were all re-sized to fit either a spread in the book or a full single page (vertical).
But quite a few of the images that have been imported to the InDesign document have been made smaller than a full page spread or single page within the InDesign document itself.  Some are 70% smaller than full page or full spread.  The original JPEGs and/or TIFFs were not resized.
The InDesign document, then, is linking to an original size image ... even though the same image in the InDesign document may be smaller as well as cropped somewhat.
So my question is: before creating the PDF, do I need to go back to the original JPEGs, resize/crop them to match what I've laid out in InDesign and then re-import them?  I hope not.  That feels like nearly having to start all over!  I've searched extensively for an answer to my question, but I've not found anything even remotely close to this topic.
As a test, today I created one complete PDF straight from the InDesign file (almost 200 pages), and it looks really good ... 99% close to the original images.  But with images that have been reduced as much as 60-70%, I'm seeing a slight loss of detail and some plugging up in the shadows; not much, mind you ... but enough to cause me some concern.  I believe the reduced images are losing a touch of crispness.
I know if I were doing a straight size reduction in Photoshop and saving a pic as a resized JPEG or TIF image, I'd be re-sampling and brightening the reduced image (a little), adding some local contrast, adding micro contrast, etc to compensate for the lost data.  Seems to me the same thing needs to be done with images made smaller within InDesign.  Then again, maybe not.
Your experienced advice and suggestions are very welcomed.  Thanks in advance.

Answer 1

Alicia'sDad: As I read your original post, I have a lot of trouble telling what your real question is.
You make a lot of statements and sound very confused?
Re-reading several times, I gather your concern is that the image quality in your PDF output appears to be degraded? Is that correct?
If so, you should tell us how you are viewing the PDF file (on paper? viewing it on-screen or printing it from Adobe Reader? From Acrobat Pro? From Preview.app? Non-Adobe software has been known to do bad things to PDF quality.)
What are the actual and effective PPI of the images in question?
You write:
So my question is: before creating the PDF, do I need to go back to the original JPEGs, resize/crop them to match what I've laid out in InDesign and then re-import them?  I hope not.  That feels like nearly having to start all over!  I've searched extensively for an answer to my question, but I've not found anything even remotely close to this topic.
You should not have to do this. Certainly unless you have some higher-resolution source material, you are unlikely to get significantly different downsampling from Photoshop than InDesign will produce.
But also, tell us your output device. What kind of resolutions are we takling about? If you're printing, say, a 300ppi black and white image on a 300 dpi laser printer, you should realize that a 300dpi laser printer can only produce about 60lpi because of halftoning, so a 300ppi greyscale image won't look much different than a 100ppi greyscale image on paper. Etc. (Though on screen is very very different.)
Good to know that re-sizing within InDesign during export does re-sampling.  I wasn't aware of that.  Thanks again.
Carefully read the settings in the PDF Export dialog. All things being equal, you should probably use the PDF/X preset.
Thanks for the response Peter.  I'm not sure what you mean by using Zip compression to "make the difference."  What "difference" are you referring to?
When you export to PDF, you have settings like this:
It's hard for me to imagine you are in a situation where this really matters, so I'm a bit skeptical. But depeannding on setting here, InDesign will do several things. It will resample your images to a reasonable ppi for a decent output device (e.g. a 1200ppi/200lpi imagesetter or comparable), and it will compress them. The default compression is JPEG, which does mean that it can introduce compression artifacts. If you change the compression to ZIP, then there will be no compression artifacts because ZIP is a lossless compression. The compression will also be less effective, so your file size may increase, but that's probably not a problem or real consideration.
p.s.: I think it's best to keep the font size in your posts the default. If everyone made their posts bigger it'd just be weird.