Following up to this. I notice that the background jpeg image is in fact scaled within it's container to 24%. Perhaps this is why pass-through isn't working? This leads me to another question. The resolution of the image out of photoshop is exactly what I want for a 300dpi A4 sized image. So why the scale? I don't want it to scale this, I want exactly 300 dpi. What the heck is indesign doing here? The image is scaled to 24% inside it's container. Then I export the PDF at 300 dpi. Is it scaling it back up, thus resampling twice?
I think I need to somehow get indesign to interpret the jpeg as 300 dpi, then it will appear unscaled inside its container. Is this possible?
I'm totally lost here. Any advice is greatly appreciated.
What are the Actual and Effective resolution values for the image when you select it in ID and check the link info?
The resolution is 3508x2480
Actual ppi: 72
Effective ppi: 300
As far as I know, there's no way to set ppi/dpi in jpegs. So unless theres a feature similar to premier's "interpret footage." I'm not sure this workflow is going to work for me. Really a bummer, this seemed like the best workflow for making a hybrid document that works well on both screen and print.
If you save the jpeg in Photoshop it will have an actual ppi value equal to the dimensions you set in the image size dialog.
This is set to 300dpi in Photoshop's Image size. When I export a tiff, it retains this value, but exporting a jpeg, and the value reverts to 72.
Is there anyway to achieve this?
No. InDesign takes the incoming pixels (with or without compression artifacts) and, if you choose to compress, performs new compression on those pixels on export. You would be better off saving in a lossless format like PSD and letting any needed compression happen on export.
When I export a tiff, it retains this value, but exporting a jpeg, and the value reverts to 72...
As far as I know, there's no way to set ppi/dpi in jpegs.
If you use Save For Web the output is to the chosen pixel dimensions at 72ppi. If you want to retain the file's ppi use Save As to JPEG
The effective res is all that matters because it takes into account the scaling. If you check the ppi of your 72ppi image scaled to 24% in AcrobatPro (Output Preview>Object Inspector>click on the image) you'll see that is 300ppi.
You can see what happens if you compare an uncompressed PSD with an overly compressed jpeg placed in ID.
The two side by side in Photoshop where you can clearly see the artifacts in the jpeg:
Placed in ID the jpeg's overly compressed pixels are still visible—these are the pixels that get exported
If I export to PDF with minimum quality you can see the compression artifacts in the PSD and newly added artifacts in the jpeg: