Images on your monitor typically have lots of bright light shining through them. That can make your images seem brighter than they really are. When your book is printed, those images might look darker than expected.
Luckily, there's an easy way to check and adjust the brightness of your images. You can use an image editing program such as Photoshop, iPhoto, Photos, Preview, or whatever you have available. Look for a feature in those programs called levels or the histogram.
This photo might look OK on screen, especially if your monitor brightness is turned up high...
...but when I use the Levels tool in Photoshop (below) I can see it's actually pretty dark. There's very little pure white in the image. Those "white" rabbits would actually look a bit grey in the printed book if printed as-is.
How do I know this? See the graph below that looks like a mountain range? That's the histogram.
The left side of the histogram shows the levels of black. The right side shows the amount of white.
Most images should have a full range, meaning the histogram should go all the way across. But here it doesn't go all the way to the right because there's very little white in the image.
You can adjust the black or white levels in the image using the arrows below the histogram.
The left arrow adjusts the black levels while the right arrow adjusts the white levels, making whites, well, whiter. (The middle arrow adjusts the midtones, which we'll ignore for now).
To increase the amount of white (and brighten the white areas) slide the right arrow left. There's no exact formula as to how much (every image is different) but aiming for the right edge of the histogram, or just a bit past it, is a good start.
Below, notice where the right arrow is now, and how the rabbit is no longer grey. This rabbit would look white in print.
Don't overdo it, though. If you brighten an image too much, things may look washed out on screen and you'll lose detail. Below, I've dragged the right arrow too far the left. The image is now washed out.
With this simple tool and some (moderate) adjustments you can get better results in your printed book.
A few final reminders
- Note that every image is different and your results may vary.
- Ultimately you, the author, are responsible for the content of your book, including the brightness of your images.
- You should always order and review a single, Blurb-printed copy before you place a larger order or when working on an important project, in case you need to make revisions later).
Have questions about your printed book? Please contact customer support.