There's a good chance you are compressing the Jpeg too much in order to make it "emailable."
FYI (In case it'll help someone):
When working in photoshop, you should never save an on-going project as a Jpeg. This is because everytime you save a Jpeg you actually degrade the image quality. Without getting technical, let's just say that it is very much like making a photocopy of a photocopy over and over again. Recall those copies that have been recopied so much they're hardly readable!
So save even your on-going
PS projects as a PSD. This'll be the default if you have layers in the file. When you have a "flattened" file, we should all be saving these files as a DNG or TIFF. Tiff and Jpeg are the most universal. DNG and Tiff do not compress the file at all, so there's no degridation if the image.
In photoshop there's a "Quality" slider that appears when you are saving a Jpeg. You should save your Jpeg at no lower than a "level 10." This will reduce your file size quite a lot from a "size 12" -which is the maximum, least compressed jpeg in photoshop. The differences between a "10 and 12" of the same Jpeg are too small to see.
** Note: Merely Cutting or Copying and Saving or making a CD (or emailing etc.) a Jpeg is not the same as opening the jpeg in
PS or other
image editing software and saving as a Jpeg again. With the former you are duplicating the data in the file, with the latter, you are re-compressing the data that was already compressed.
-The copy of a copy of a copy scenario.
When sending a job to a printer:
In Photoshop, make sure you either use a resolution of 240-300ppi and your image size is equal to the final printed size. Beyond this, we should always contact the printer and ask them what parameters they'd prefer. This includes file format.
In my opinion and experience, if I were working on something to be off-set printed and I was working in photoshop, I'd save the file as a .PDF with the highest quality .PDF settings I could command. -Be mindful that making a .PDF gives us the opportunity to reduce file size for emailing. -But this is meant for
viewing on screen -NOT printing.
I hope I helped : )
-E!