Preparing an image for a book is not quite the same as printing your image. With a book, the viewing distance is set to a standard; therefore, there is a more rigorous standard around resolution. If you are working with a book designer, you likely will be guided by their advice, and this article may only provide insight into why certain things are required.
Often, requests to prove an image for a publication will fail to specify the format and will ask for a specific size and resolution but not provide you with directions on how to create a file to that specification. If you are asked to provide images for a publication and are given these sorts of instructions, then the following may be of interest. Hopefully, they will help you put your best foot forward.
Using the Right File Format
A JPG or TIFF file will be best when you are not working with a designer. These can be created easily by exporting them from your photo processing programs. The export process will allow you to set not just the file format but also the resolution and size of the image. If you do not use photo processing programs, Mac has Preview, and Windows has Microsoft Photos.
So, what is the difference between JPG and TIFF? JPG files are significantly smaller than TIFF files and much easier to send by email. However they, they use “lossy” compression, unlike TIFFs. This means every time you save a JPG file, its quality deteriorates. TIFF files, on the other hand, although larger, maintain their quality no matter how many times you save your file. The image below illustrates how JPG files degrade after multiple saves.
Typically, most individuals will have a JPG file, which will work well provided that the resolution is correct, the camera has produced a good-quality image, and the files have not been saved multiple times.
If someone is laying out a book for you, a RAW file may be more desirable, so it is good to check. Keep in mind RAW here is being used as a generic term; each camera will have a different RAW format: ARW (Sony), NEF (Nikon), CRW (Canon), RAF (Fujifilm), ORF (Olympus), RAW (Leica), etc. RAW files have the advantage of containing significantly more information than a JPG file; this allows a book designer to correct camera errors and bring more uniformity to the publication.
If you export the image from a processing program, you may have the following options: JPG, TIFF, PNG, DNG and PSD.
|Widely supported small size
|Loss of quality after multiple saves
|high quality pictures, and web images
|Limited colour support
|Primarily used for web images
|larger file size, not widely supported
|Icons, logos transparent images, web images
|Large File, high quality
|Can quickly become a very large file
|Used widely in printing
|Large files may need to be converted for some uses
|Used by graphic designers
Camera errors can include mixed lighting problems, discolouring walls that should be white, objects that should be out of frame in a frame and angular distortions. Most of these are more easily corrected using a RAW file, and some of these are very difficult and sometimes impossible to correct using a JPG file. Focus issues due to the focus point not being set on the subject or setting your speed so slow the camera registers you hand movement, which both result in blurred image can not be fixed.
Resolution Coming from a Camera
The camera you use to create the image will determine the image resolution; for example, a 24mp camera will usually be 6000 X 4000 pixels, keeping in mind the file size, which may be 30MB or 48MB, does not tell you the resolution. The RAW image might be 30MB but converted to a TIFF; it could be 137MB or, as a JPG, 14MB, and all three could have the same resolution.
Two key elements that determine the resolution are DPI (dots per inch) or pixels per inch. In the image below, you can see a typical 24MP image from a camera. It produces a photo with a resolution of 240 pixels per inch and 25 inches on its longest side. Any resolution between 240dpi and 300dpi provides good print quality.
Typically, for book publishing, one would want to make sure the resolution was between 240 and 300 dpi and perhaps one or two inches more than the widest dimension of the book. This may not be technically necessary, but a little “fudge” room is always good. So, if the longest side of the book is ten by ten, I would not want the image to be less than 10 inches and not less than 240 dpi.
Why Printing and Image for Wall Display is Different
Printing images for display on a wall involves taking into account the “circle of confusion,” which calculates the ability of an image to appear sharp, given the distance from which the viewer sees the image. I have left some links below if you want to read up on this, but I will not go into it in this article, only to say lower resolution images can appear sharp when enlarged and viewed from a distance. After all, the view distance of a work on a gallery wall often varies from that of a book. In today’s world of printing large images, individuals often step forward to look at the details of a print, so in these cases, the circle of confusion is misleading. I am not convinced that applying this theory to art photography is in the artist’s best interest. It likely works best when printing eight by ten images.
Resolution Coming from a Cell Phone
Typically, cell phones these days are 12MP. If you spend more money, the resolution can be much higher. The first image below is the size of a 12MP image from a typical smartphone. You will notice that although the image seems to be 14 inches on the longest side, the resolution is only 72 pixels per inch. This resolution is excellent for viewing on a computer screen but not for a book. If the resolution is changed to 300dpi, then the size of the image is only 3.4 inches on the longest edge. This is why a typical image from a cell phone does not translate well for most standard-size books, unless the image in the book is only 3 or 4 inches on its longest side.
Resizing and Cropping
Resizing and cropping both affect the quality of the image. Cropping reduces the size of an image, so if you have cropped your image to get rid of unwanted material, you have reduced the resolution. If this is the case or you are using a cell phone image, you might consider increasing the image size by resizing. This process basically uses an algorithm to produce more pixels based on pixels in the original image. Generally speaking, although the image’s resolution has been increased, the quality is not necessarily better. In many cases, it has just become fuzzier. Sometimes this method is necessary as a last resort, but an expert best does it to minimize the loss of quality. I have included references on the processing of resizing below.
Colour Space, Computer Screens and Paper
Colour space will often come up if you are working with a book designer; in this case, they will guide you through this issue. Printing uses CMYK (Cyan, Magenta, Yellow and Black) colour space, but the internet and cameras use RGB (Red, Green and Blue), to create the colours in your image. I don’t recommend that those unfamiliar with this issue attempt to convert files for printing, and conversion is unnecessary for more informal image requests. The takeaway here is the conversion process could change, to some degree, the colour and tone of your image. Also, a backlit computer screen will display colours and tones very differently from a sheet of paper. So, colour and tone must be adjusted to fit the medium through which it is presented.
- Digital File Formats, Edward Peck
- Art Preparation Guidelines, The University of Chicago Press
- What is a Digital Image, by Per Berntsen
- A Basic Guide to Circle of Confusion,
- Circle of Confusion Calculator, Photo Pills
- How to resize and Image Using Photoshop,
- Preparing Images for Print, UC Santa Cruz
- About JPEG Images and their Quality Degradation, Fstoppers
- Preparing Artwork for Print: A Guide, Knowledge Centre
- Eight Common Exposure Problems & How to Fix Them, Photography Masterclass Magazine