For book publishing, what you need to understand about graphics is how usage varies in the different formats. You’ll need to hand-adjust to produce the graphics for the various formats. Automation causes many problems. I’m just going to list the four options and their requirements, best formats, and so on.
Greyscale print with color cover
Lulu & Createspace, plus professional on-demand like Lightning source: You need to be careful. This is digital printing and we are dependent upon the quality of equipment used by the vendors and the quality control exercised in their use. In general, I have had almost no problems with Lulu with print. Lightning Source is basically the same as Lulu.
On the other hand, I have had many quality issues with Createspace. They are the 500 pound gorilla so we cannot ignore them. But, be careful and make sure your artwork is conservative. In all cases, the problems were solved by flattening Photoshop images or re-exporting PDFs limited to Acrobat 4 compatibility [which flattens all transparency]. In one case I had to rasterize a PDF at 300 dpi for an interior graphic of a Createspace book. Don’t argue. Just give them what they ask for.
Bitmap images: 300 dpi grayscale PSDs, TIFFs, and PDFs. Lulu/LS can handle layered PSDs with transparency. Createspace sometimes has trouble, although I’ve never had any issues with transparent backgrounds for either of them. Createspace sometimes drops color lighter than 10% (they have a tendency to print a little light).
Vector images: PDFs, AIs, and EPSs. I use Acrobat 5 compatible PDFs for Lulu and Acrobat 4 compatible PDFs for Createspace. Lulu’s printing of these images is much sharper. Createspace sometimes drops light tints.
Createspace’s books are acceptable. Lulu’s books are often excellent. This is on-demand digital printing. So, we are talking professional copy machines—with toner instead of ink.
CMYK artwork: Unless you are using Lightning source where they require CMYK, I now recommend using RGB. There are a few problems with this. CMYK is a limited color space used with ink or toner, and it is the one which is going to be used for print. RGB is light, and you cannot print that. Brilliant colors will be toned down—sometimes a lot. However, unless you have a lot of printing [and Photoshop] experience, both Lulu and Createspace will do a better conversion of your RGB to CMYK than you will. But with a PC monitor, the color changes will often be severe. They can usually match your Mac monitor, as it is calibrated.
Remember, on-demand printing is copier technology. Think printing quality Xerox or laser printer, if it helps.
Lulu seems to prefer PDFs: I use 300 dpi RGB bitmap images with vector lineart and type. They convert the color to CMYK very well. But if you have no experience, the color shifts from your monitor will be startling. Lulu provides a vector PDF of your ISBN barcode artwork. You place it where needed. Their upload cover page gives you the necessary document size and spine widths. I assemble them in InDesign and export them with Acrobat 5 compatibility and have had no problems.
Createspace demands Photoshop PDF files: Photoshop PDFs are strange beasts with quite limited options. Their recommended workflow starts with assembling a layered PSD on their template. Their PNG template has a guides layer showing bleed trim areas, spine width, and maximum area for type. You are required to leave a specific area for the ISBN and they imprint the ISBN into that area. They leave very little room for type on the spine and enforce their rules strictly. They require 300 dpi RGB.
I design my covers in InDesign, export them as a PDF, and import the PDF to the Photoshop template [the PNG saved to a PSD]. Once everything is in position, I flatten the image and save it to the Photoshop PDF format. This gives you much better quality back covers and spines. They accept nothing else so far.
This required rasterization does soften the type (and often fattens it up quite a bit) and they can have problems printing rules thinner than three-quarter point, especially over a colored background (though normally they can print half-point rules with no problem). Make sure your type is large enough and clear enough to handle this.
Color printing throughout (Lulu & Createspace)
I haven’t done much full-color printing. When I have, I’ve used Lulu. Every thing I said about greyscale printing still applies. Lulu works well with CMYK. My best guess is that Createspace likes RGB better (they might require it). Graphics In InDesign was my first full-color book with Createspace. As far as I know there were no issues with it. As print sales shrink, full-color print becomes more viable [strange].
Downloadable PDFs (Lulu, Gumroad, Adobe’s Publish Online, Kindle Textbooks, & Scribd)
Now that Lulu has separated the downloadable PDF from the printed version, there is no reason to avoid full-color. The same is true with Scribd and Gumroad. Lulu & Gumroad can easily handle everything that you can print. Scribd is geared more toward the Word user and has trouble with fancy stuff. For example, Scribd has trouble with paragraph rules, in general, and ruins rules with gradients. Scribd seems to be using a non-Adobe PDF reader, but I have no proof of that.
Adobe’s new Publish Online only works for free stuff, at this point. But it is easy, free, and fast. it is great for quick distribution of freebies, like free previews of your new releases. Of course, it only works with InDesign.
The bottom line is that you need to be a bit careful proofing Scribd’s online PDFs. Also Scribd is more geared to free stuff. But they can give you a lot of eyeballs. I’ve found they work very well for customized free previews of your books. Their subscription model seems to have messed things up a bit
Lulu has always sold a lot of downloadable PDFs for me. That has slowed a lot now that they’ve moved PDFs to their own pages (there used to be a downloadable option on the print pages).
Kindle Textbooks: These are encapsulated PDFs produced by Kindle’s free Kindle Textbook Creator to convert your uploaded print PDF. They work very well as companion ebooks to a bible study or any other book used in a classroom, Sunday School, or Bible study setting. This is because they have the same pages and numbering as the print version. You can offer a Kindle textbook much cheaper [to help poor students] and still make more money than you do with print. I’ve been very surprised at how well they sell. Plus, because they are unique to Kindle, you can always keep them in KDP Select, even if your regular reflowable ebook is not. (Of course, that may change.)
- RGB color
- Vector if possible [InDesign or Illustrator graphics]: usually imported PDFs, though you can place AI (Illustrator) files directly also.
- Bitmaps [Photoshop]: Go for 300 dpi bitmaps: unless the file size gets too large. Scribd seems to have problems with files sizes much over 5 MB. Lulu does not seem to have those issues. Gumroad is limited to 50 MB.
- Acrobat 5 compatible: seems to work for either, transparency has no issues I know of.
EPUBs (iBooks, Lulu, Nook, and Kobo)
ePUBs and Kindle books will continue to change radically in the next few years…
Think of this as Web design. It’ll help conceptually. All graphics are bitmaps—no vectors allowed, yet. The spec supports SVG, but that has not happened yet in reality. I expect this to change fairly soon, and having a vector format for ePUBs (and Kindle) will change the game a lot. The iBookstore supports ePUBs which are far superior typographically and graphically.
Maximum image size: 600×800 pixels: this has become the interim standard. In specific, image sizes are a bit more complex. The iPad full page image size is 600×860. Nook takes 600×730 pixels. Kobo uses 600×800. The new iPad has a Retina display using 1200×1600 pixels. The better Android tablets can be even higher. But the resulting file sizes make this untenable in most situations.
RGB: Use color to help, even if the graphics in print are grayscale
JPEGs, PNGs, or GIFs: Use the Save for Web option to help control file sizes. Keep your JPEGs at Medium or High compression to avoid the bad JPEG artifacts. And, DO NOT recompress an existing JPEG, you’ll make the artifacts much worse. Always keep a PSD or TIFF original.
Right now, iBooks is the one really pushing the envelope: They can handle custom-placed anchored objects and gradients applied to type via paragraph styles. Single cell tables can be used for sidebars (with care). Embedded fonts work very well here. As a result, ePUBs in the iBookstore are several steps above ePUBs provided anywhere else. However, people reading ebooks tend to be unresponsive to better type in novels. But much of that is caused by people trying to do typography with a word processor [think very ugly].
Currently, tables and lists often need to be converted to a graphic. The resulting 72-dpi images are really rough on the reader. Only iBooks handles tables well, at this point. This will change a lot in the coming years.
Kindle KDP (Kindle Direct Publishing)
Your KDP account to publish your books on Kindle has links to give you the most current requirements. The new format is called Kindle Advanced Typography [KFX], and it was developed for Fire. At present, things are a mess. I was converting my ePUBs with Kindle Previewer to use in KDP with no known problems. But Previewer quit working with OSX.11 [El Capitan]. The new Kindle Previewer 3.0 has solved that problem.
In addition, there is a basic problem. Once Amazon gets a hold of them, they can (and sometimes do) change things without notice, outside of your control. Again, for novels, this is no big deal. For complex non-fiction used for teaching and study groups, this can be a real problem.
The maximum image size was 127K: Even a byte or two larger and Kindle would resize your image (with very bad results). It was so bad they warned us. Supposedly that is no longer true. But a lot of it is at the whim of Kindle, often after the book is uploaded and released. The better typography of the KFX format is done that way—without your knowledge or approval, after it is uploaded.