My heart nearly broke when I checked the resolution of a photo in a client’s family history/memoir I was preparing for upload to CreateSpace.com for printing copies for family members. When I copied the document photo and pasted it into IrfanView (my favorite free photo editor for low-end needs), I saw that the resolution was only 72 dpi (dots or pixels per inch). That’s a small fraction of the pixel density CreateSpace requires. This was the case with nearly all the several dozen photos in the book.
I had the gut-wrenching task of explaining to my client that she had a choice: I could resample the existing images to trick CreateSpace into believing they were 300 dpi . . . or she could rescan them.
How I wished that she, like the majority of people scanning old family photos, knew all along about scanning at a minimum resolution of 300 dpi. Here’s why it matters:
CreateSpace will sound an alarm when it analyzes an uploaded document and finds even one image of less than 300 dpi. For good reason. Lo-res images will look even worse in print than they do onscreen when zoomed above 100%. Ignore that warning at your own risk.
The left photo above is scanned at original size at 72 dpi. The image on the right is exactly the same picture, scanned at 300 dpi. Notice the crisp, clear detail in the high-res version compared to the blurry approximation on the left. That’s the sort of result you can expect with any image printed at 72 dpi.
My client wanted her volume to be top quality in every respect, so she opted to rescan as many photos as she still had available. For the rest, we stuck with small sizes and I resampled the existing photos as 300 dpi to stabilize them for printing. That turned off the CreateSpace alarms, but nothing could recreate lost detail. Still, those photos add value to the story and they are better than nothing.
Many of us scanned hundreds of pictures fifteen or twenty years ago when scanner technology was new and file size a concern. A 3” x 4.75” photo scanned at 300 dpi produces a file larger than the 1.44 megabyte capacity of the 3.5” floppy disks we used back then. We scanned at 72, or perhaps 96 dpi. I have a few hundred files like that myself, with the originals clear across the country, as many of hers are now. Those low-res files will work fine for eBooks and online viewing, but they are not print-worthy.
The tips below will help you get the best possible results for your publishing projects. If you decide to have someone else do layout for you, getting the photos right before you hand over the file will keep costs down and save you lots of aggravation.
Resolution – the number of dots or pixels per inch. At 72 dpi, a square inch of image will have 72 pixels horizontally x 72 pixels vertically for a total of 5184pixels. At 300 dpi, that will be 300 x 300 for a total of 90,000, allowing for more than 17 times as much detail.
Resample – this word carries a touch of magic. If you change the resolution of an image, software uses samples from the image to calculate how to best condense or expand information to cover the desired amount of space. Increasing resolution spreads existing information thinner and is unable to add more detail.
Tips for preparing photos for publication
Scan at 300 dpi and 100% resolution – or higher. If you have a photo that’s 2” x 3”, scan it at 600 dpi or higher to give you a high quality image printable at larger sizes so you can enlarge it enough to let people see detail. 600 dpi will allow you to double the size of the original in print. 900 lets you print up to three times larger. Most old film photos lack the crisp resolution needed to successfully enlarge more than that.
Resample and enhance. If you aren’t able to rescan those old images, resample them to 300 dpi turn off the alarm.
Size in Microsoft Word to fit space on the page, then copy the image and paste into IrfanView or another editor to check resolution. Resample to 300 dpi at the precise size of the image in your manuscript. Replace the “temp” image with the resized one.
This matters because Word does a poor job of resampling, and images resized within the document generally look terrible when printed. This is partly due to changing the resolution as you resize in Word. Resizing is a nuisance, but worth the effort. I’ve tried not doing it and the results were not pretty.
Crop images with a photo editor. You can do this in Word, and it might be okay, if you start with a 300 dpi image and don’t change anything else about its size. Check the quality of the image in your proof copy of the finished book. For best results, crop in IrfanView, Photoshop Elements, or something similar and check to make sure the final image is 300 dpi.
Use an image editor to convert color images to grayscale if you plan to print in black and white. You can print from color or use Word’s image editing function to do this, but it’s not your best choice.
I’ll do another post soon on using your scanner interface. For now, scan big and pose questions in comments.
Write now: take a break from writing and scan a photo or two. Insert it in Word and play around with sizing. Download IrfanView and practice resampling. Tip: Resizing is on the Image menu. Ctrl+R will get take you right there. Have fun!