How to Check Image Size & Resolution



In this video, I’ll show you how to check the size and resolution of your images using Adobe Photoshop. There are many different programs you can use to view your images and most of them will allow you to access the images properties or attributes from the menu bar. If you can't find the size and resolution in one program, try another. If all else fails, you can always send the image to us and we can check it for you. 

First lets briefly review the requirements and then we’ll go into Photoshop to check for them. If you’re submitting images for your book’s cover or interior, they need to have a resolution of no less than 300 ppi or pixels per inch. In addition, images for your interior need to be roughly four by six inches or larger. If they’re for the cover they should be slightly bigger than the cover itself, adding at least an eighth of an inch to the cover’s top, bottom, and outside edge. To demonstrate how size and resolution work together, I have a few examples I’d like to show you. 

First let’s look at this photograph. Let’s say we are interested in placing this image on a page inside a six by nine book. Let’s also say we want this image to fit the width of the page, which would be six inches. In Adobe Photoshop, you can check the size and resolution by going to Image and Image Size. In the window that pops up, we see that the image is six-and-a-half inches wide, which is enough to span the width of the page. Unfortunately, the resolution of the image is only 150 pixels per inch, only half the resolution of what is required for publication.

However, in Adobe Photoshop and some other programs, you are able to change the size or resolution of an image. But, when doing this you need to be very careful that changing one aspect of the image doesn’t negatively affect another aspect. For example, if we change the resolution of this image to 300 ppi you’ll see that the image gets smaller. It is now only three-and-a-quarter inches wide, no longer big enough to span the width of the final page. But there is one other solution when using Photoshop or other image manipulation software. Before changing the resolution, make sure Resample Image is selected, and if you have the option, choose a bicubic setting that helps smooth out enlargement. Now when we change the resolution to 300 ppi the width and height remain the same. This process is called resampling, and while it might get your image to meet the technical requirements of our printer, it is not always a perfect solution. When you resample an image this way, it might look blurry or pixilated. Sometimes, like in this example, the tradeoff is acceptable but other times you will notice the quality of your image degrades so badly that the only remaining option will be to rescan the original photograph or artwork if you have it.

If you have the original hardcopy image, but are not able to rescan it yourself, you might be able to find scanning services at your local office supply store. We also offer our own scanning services. If sending an image for scanning, we recommend making a high quality photocopy for submission so that you don’t take the chance of losing your original image in the mail. See our fee schedule or contact a representative to learn more about our scanning services. 

Let’s look at another photo. Let’s say we want this image to fill an entire page in a five by eight size book. By going to Image and Image Size, we can see that this photo is only two inches wide and just over three inches tall, not nearly big enough to fill a five by eight size page. Its resolution is also very low, only 72 ppi. Incidentally, 72 ppi is the standard resolution for images on the internet. Their low resolution makes them faster to download when you’re surfing the net but it makes them bad candidates for publication, so if you’re pulling images off the Web, you want to be sure to check their resolutions, and that you have legal permission to reproduce them. Let’s see if we can change this image’s properties to meet printer requirements. If we select the resampling button and change the resolution to 300 ppi we can use this image, but it can only be two inches wide. If we tried making it any bigger, it would lose resolution and become blurry, or pixilated. If you zoom in on this image, you can see what this looks like. This is what would happen if we tried to make the image fill a page in a five by eight book. It just isn't possible. The only solution would be to rescan the original photograph at a higher resolution.  

Now let’s look at a couple of images we might want to use on the cover of a book. Let’s say we want to use this photo to fit width-wise across the middle of the front cover, and our book is six by nine inches. The image is six inches wide, almost big enough to fit the width of the cover. Remember that when trying to fill a cover you have to add an eighth of an inch to the top, bottom or outside edge of the cover. In this example, the image wasn’t going to touch the top or the bottom of the cover, but it was going to touch up against the outside edge of the cover. In that case, the image would need to be at least six-and-one-eighth of an inch wide. We also notice that the resolution of the image is only 250 ppi, slightly less than the required 300. It would be best to rescan this image if possible, but if you do not have the original hardcopy image, you might be able to resample the image to meet printer requirements. First select the Resample Image button, then change the resolution to the required 300 ppi and change the width to six-and-an-eighth, or 6.125. Click OK. Next it is a good idea to go to View and Actual Pixels. If you think the image still looks pretty crisp and clear, it is probably safe to use on your cover, but if you notice any loss of quality, it is better to try rescanning the original hardcopy image or finding another image to use. 

Let’s look at one more image. Let’s say this image is an original painting you made to fill your six by nine cover. Remember that in order to fill a cover, we have to add an eighth of an inch of bleed space at the top, bottom and outside edge of the cover. When we look at its properties, we see that it is 300 ppi. The width of the image is six-and-a-half inches, a little more than the minimum of six-and-an-eighth for this example. The height of the image is a little more than seven-and-three-quarters. If we wanted the image to fill the six by nine cover, the height would need to be nine-and-a-quarter inches, including an eighth-inch at the top and an eighth-inch at the bottom for bleed space. This image could fit the width of your cover, but could not fit the height. If you could rescan this image so that the height were nine-and-a-quarter inches, you could then crop the sides of the image until it fit the width of the six by nine book cover. 

When creating original artwork for your cover, it is a good idea to know the dimensions of your book’s final cover before beginning and to keep in mind that the outer eighth-inch at the top, bottom and outside edge will be cropped off at the printer. 

If you have any questions about images, please give us a call at 1-800-AUTHORS, and we’ll be happy to talk with you about them.