Images for your book

Summary

• Images should be provided in either TIF or JPG format

• Image resolution is measured in ppi (pixels per inch) or dpi (dots per inch). For our purposes, we can assume them to be the same.

• The resolution of images created for display on computer screens is usually 72 ppi and seldom more than 96 ppi.

• The resolution of photographic images and illustrations for print (book covers and pages) should be at least 300 ppi. Therefore, a photographic image to be used on a 6 in. wide book cover should be at least 1800 pixels wide (6 in. X 300 ppi).

• Images for the inside of a 6" wide book with 0.75" left and right margins (4.5" text block) should be at least 1350 pixels wide (4.5 x 300).

•  The resolution of line art* images for print (book covers and pages) should be at least 600 ppi. Therefore, a line art image to be used on a 6 in. wide book cover should be at least 3600 pixels wide (6 in. X 600 ppi).

*(Line art is any image other than a photograph that consists of distinct straight and curved lines placed against a (usually plain) background, without gradations in shade. Line art illustrations are drawn by programs such as Corel Draw and Adobe Illustrator.)

Read further for more information.

Taking photos for your book

• Take photos with your digital camera at very hi-res (high resolution), preferably in TIF format.

• Photos for a 6 inch (15.25 cm) wide book cover should be at least 1800 pixels wide (300 PPI (pixels per inch)).

• Photos that are to be 5" wide in your book should be 1250 to 1500 pixels wide (250 to 300 PPI).

• Do not compress your photo files. Compression options in some programs such as Microsoft Office Picture Manager reduce both file size and picture dimensions based on how you intend to use the picture, such as in web pages, e-mails or printed material (books).

Digital photo files

• If you already have all your photos taken, send the photo files you have (uncompressed) without making any changes to them.

• Send them as email attachments or or using a large file sending service such as found on my Contact page, not as insertions in an email or insertions in a Word document.
  

• I'll review them and determine their suitability for use in your book.

• The resolution of hi-res files can be decreased, but the resolution of low-res files can not be increased. The only way to properly increase the resolution is to re-scan the original photos at a higher resolution.
  

• If we have to work with what we have (lower resolution than normally considered acceptable) I'll do what I can to improve their appearance in the book. However, don't expect them to look as good as a proper hi-res image. 
  

• Computer screen shots and images dragged from web sites are usually about 96 PPI -- lower than normally considered acceptable, but as above, I'll do what I can to improve their appearance in the book. 

• Pixel and resolution information about a picture file can be obtained by opening the file folder, right clicking on the file name and selecting Details.

Print photos and scanning

• If your photos are in print form taken by a film camera, they will need to be scanned and converted into digital form.

• Scanners usually represent resolution in DPI (dots per inch). For our purposes, consider them the same as PPI (pixels per inch).

• scan the photo at 300 DPI if you want it to remain the same size in the book as the original.

• scan the photo at 600 DPI  if, in the book, you want it to be scaled to twice the size of original

• scan line art at twice the photo resolution (Line art is any image that consists of distinct straight and curved lines placed against a (usually plain) background, without gradations in shade.)

• scan all the photos and line art to a TIF format

Vector Graphics

• A vector graphic is a computer-made image that is made up of points, lines, and curves that are based upon mathematical equations, rather than designated amount of pixels.
  This means that no matter how large or small or how close you zoom in on the image, the lines, curves, and points remain smooth. There will never be jagged lines or blurriness with this kind of image, no matter how much it is enlarged. Also colors are separated into specific shape areas, which makes changing colors within these images as easy as the click of a button.

• If a vector image needs to be scanned, it should be scanned at 600 dpi to preserve the crispness of the edges.
  

• Type fonts are vector graphics, therefor type should not be scanned as part of a 300 dpi image, but rather placed over the image later when the page is being formatted for print in order to preserve it's crispness.
  

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Below is more detailed information about photos

Using Photos in Your Book:

Understanding Print Resolution

by  Joel Friedlander
    
I was talking to an author the other day about photos he wanted to put in his book. I looked at the image files he had sent over with his manuscript.

“They look great,” the author told me, “I’ve put them into the book in Microsoft Word, I have it on the screen in front of me, it looks terrific.”

“Uhm, I don’t think these are going to work in your book,” I said.

“What do you mean, they seem fine to me? What’s wrong with them?”

What the author couldn’t see was that I hadn’t even opened the image files. I didn’t need to, all I had to do was look at the size of the files in the email attachment panel. One was 4k, the others were 8k or 10K or even 24k in size.

“Look, I explained, “there’s a big difference in what we use online, when you’re only going to be looking at them on a screen, and what we need when we go to print these same photos. I know it doesn’t seem to make sense, but the images you’re looking at on your screen are 72 dots-per-inch (dpi). We need files that are 300 dpi. And if they aren’t 300 dpi, there’s a good chance the printer will reject your job.”

Using File Size to Quickly Gauge Reproduction Size

I want to show you how to calculate this for yourself, even if you just want to be able to tell from the files you’re looking at if they are likely to work.

Okay, we’re going to do a little math now, but I promise it won’t hurt (too much).

Let’s look at the typical sizes of photographs or other grayscale images you might use in a typical book. I’ve taken a page from a 6″ x 9″ book and divided the space within the margins:

A full page illustration can be as large as 4.25″ x 7.6″ without going into the margins or bleeding off the page.
A half page is 4.25″ x 3.8″
A quarter page is 2.2″ x 3.8″
Now, taking what we know—that graphics have to be 300 dots per inch at their reproduction size let’s do some calculating:

Our full-page illustration will need to have:
4.25″ wide x 300 dots per inch = 1275 dots, or pixels
7.6″ tall x 300 dots per inch = 2280 pixels
The photo that’s 1275 x 2280 will have a total of 2,907,000 pixels. That’s about 3 MB of data.

Our half-page illustration:
4.25″ wide x 300 dpi = 1275 pixels
3.8″ tall x 300 dpi = 1140 pixels
So the photo will be 1275 x 1140 or a total of 1,453,500 pixels, or about 1.5 MB.

Our quarter-page illustration:
2.2″ wide x 300 dpi = 660 pixels
3.8″ tall x 300 dpi = 1140 pixels
The photo will be 660 x 1140 or a total of 753,060, or about 800 KB.

Image Compression Makes a Difference

But wait. Most photos are saved as JPG files. Leaving aside for a moment whether this is a good idea (it’s not a good idea if you plan to keep editing the images). One of the reasons we use JPG online is for its ability to compress the files into much smaller sizes.

But it’s good to know what’s actually in the files. Let’s say we’ve saved each of our illustrations in both TIFF format with no compression, and JPG format with the compression set for maximum image quality. Here’s what our final file sizes look like, as reported by the Mac operating system:

Full page, TIFF:         2,989,336 bytes   or 2,989 KB
Full page, JPG:             841,578 bytes   or    842 KB
Half page, TIFF:         1,560,237 bytes  or 1,560 KB
Half page, JPG:             537,242 bytes  or    537 KB
Quarter page, TIFF:       844,607 bytes  or    845 KB
Quarter page, JPG:         351,015 bytes or    351 KB

And now you know why I knew many of this author’s photos were too small (and probably screen grabs at 72 dpi, way smaller than what’s needed for offset printing).

Even for a quarter page photo, saved with compression, the file size ought to be around 350 KB. Obviously, photo files showing a file size of 50 KB or 100 KB will not be usable for a printed book.

By the way, this is another reason it makes sense to create the layouts and artwork needed for print production for your book before addressing ebook versions. You need the high resolution images for print. While it’s easy to reduce the size and resolution of your images, it’s not possible to add detail and data (or resolution) back into the image once it’s gone.

When planning to add photos to your book, make sure you have files with enough resolution to print at the size you want in the finished product

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Scanning Images for your Book

Photos in a quality printed book should be at a resolution of 300 dots per inch (dpi). There is no point in having a higher resolution than 300 dpi since the human eye will not notice any improvement. If, however, you look at a photo with a resolution of 200 dpi beside the same photo with a resolution of 300 dpi, you may notice that the lower resolution photo appears to be a bit patchy by comparison. The flow of one shade into another is not as smooth as in the higher resolution photo.

Photos should therefore ideally be scanned at a resolution that will result in an image file that is 300 dpi.

Some examples:

Let’s say you have a picture that is 2” wide.
If you scan it at 300 dpi, it will be 2” wide in the finished book.
If you scan it at 150 dpi, it will be 1” wide in the book.
If you scan it at 600 dpi, it will be 4” wide in the book.
If you scan it at 1200 dpi, it will be 8” wide in the book.

How to calculate the required scanner dpi setting:

If you have a photo that is 3” wide and you want it to be 6” wide in the book, it should be scanned at 600 dpi
(300 dpi  x 6”/3” = 600dpi)

If you have a photo that is 10” wide and you want it to be 6” wide in the book, it should be scanned at 180 dpi
(300 dpi  x 6”/10” = 180dpi).

You don’t have to be precise in the scanner dpi setting, as long as it’s a little bigger than required. In the example above, 200 dpi would be fine. Erring on the high side is better than erring on the low side.

Line art is any image that consists of distinct straight and curved lines placed against a (usually plain) background, without gradations in shade. This type of image should be scanned at 600 dpi because our eyes can distinguish deviation from perfectly smooth edges much more acutely than shade gradations. A 45 degree angled line on a chart might appear to have a bit of a saw-tooth appearance if the resolution is below 600 dpi. The same scaling rules apply to line art as to photos.

File type: TIF or JPG.

TIF is THE leading commercial and professional image standard. TIF is the most universal and most widely supported format. TIF files for photo images are generally pretty large. Uncompressed TIF files are about the same size in bytes as the image size in memory. Regardless of the novice view, this size is a plus, not a disadvantage. Large means lots of detail, and it's a good thing. TIF stores it with recoverable full quality in a lossless format (and again, that's a good thing).

JPG file format compresses the image into smaller file sizes. It does so by removing information about the image. The higher the compression ratio, the more is lost from the image, and it is a loss that is not recoverable. JPG format may be okay for scanned images, as long as you know that the setting is for very little compression taking place, otherwise, scan your images to a TIF format.

For a more detailed look at scanning, have a look at this excellent site by Wayne Fulton: Scanning tips