You may be reading this because you uploaded an image to Octavo which was flagged with a printing warning. If you are including images in the interior of your book (or on your cover), it is vital to provide your designer with high quality images that are capable of being printed.
In general, if the size of the image in your book contains 300 or more pixels per inch your image will look smooth and crisp at an arms length when printed. If your image contains less than this there will be noticeable pixelation (blurring) in the image and text in your image may be unreadable (see below).
The clear image on the left is 300 dpi and the blurry image on the right is 72 dpi.
So what is a low quality image?
The quality of your images depends on a number of things:
- The number of pixels your digital image contains. In general if you are using a camera to capture your images you want to use one with at least 8 mega pixel resolution. Luckily most digital cameras and smartphones today will meet this standard.
- The image is captured with low quality equipment. The quality of your camera’s lens will have a big impact on the quality of the image even if it meets or exceeds the 8 mega pixel limit. In addition lightning is extremely important. Make sure your subjects are well lit and in focus.
- File format & compression. Many image formats (such as .jpg) use lossy compression, which means the image size is reduced or compressed at the expense of losing information (i.e. pixels). Use .png or .tiff (lossless formats) where possible.
So to capture quality images that you can print, use a good camera, make sure your subject is well lit and save your images in .png format.
If you are wanting to capture physical/printed photographs for use in your book, we strongly recommend using a scanner, rather than a camera, for this job. If you do this or if you get someone else to do it for you, ensure that the DPI setting on the scanner is set to at least 600 dpi – this will give you a digital image that can be printed at a larger size than the physical photograph currently is, while still keeping the file size reasonable. You can find more info on scanning here.
When you upload the image to Octavo, it will display the maximum size that the image can be printed at and a warning if the image size is low. We recommend uploading images that can be printed at least 10 inches wide at 300 dpi. Images lower than this will receive a warning. Bear in mind that, as the help text suggests, an acceptable size will depend on your book size. A book with a size of 8.5 inches wide will require an image of 6.5 inches wide in order to fill the page between the margins. Your designer will not be able to increase the width of the image, so if your book size is 8.5 inches wide and your printable image width is 4 inches, your image will not stretch across the page without visible blurring.
To replace images flagged, simply click the blue [del] button below the image to delete the image and then upload the replacement.
*A note on CMYK colour model and ink saturation (Colour photo books only):
If your book relies heavily on imagery and there is a specific way you want your images to look, it is also important that you provide your images in CMYK format with a total ink saturation value that does not exceed 240% (e.g. 60% Cyan / 40% Magenta / 40% Yellow / 100% Black), which will help to minimize how much the final printed photo appearance varies from what you see on your screen.
Some variance in appearance between screen and print display is unavoidable. Note how colours in the image on the right in RGB is slightly more vibrant than those in the left-hand image in CMYK.
Above: the difference in appearance between the CMYK (left) and RGB (right) colour models.
We hope this helps you. At Tellwell we are committed to helping you produce a book of outstanding quality. If you have further questions, please email support@tellwell.ca.
Related articles:
Can I include images in my manuscript?
How should I prepare my Manuscript for publication?