When designing digital files intended for commercial offset printing, it is essential that all of the photographs and images in your in files are high resolution. If you have ever seen printed material that contains blurry or blocky images which often provides a bad presentation, it was likely caused by incorporating low resolution images. Ensuring a high quality printed job is as simple as making sure all photos and images in your digital files are all high resolution. The information below covers the specific differences between the two and how to avoid problems.
D.P.I. or "Dots per Inch" is the measurement used within the printing and graphics design industry to determine how sharp an image is. Web graphics and online photos are normally created at 72dpi (dots per inch). This low resolution is great for the web because the images look excellent on a computer monitor and the file sizes are very small which helps web pages load faster. However, when designing graphics for commercial printing purposes, your images should be 300dpi or better, here's why.
Take a look at the example to the right. Essentially, the difference between 300dpi and 72dpi is found in the amount of pixel information (or dots) for every square inch of the image you are viewing. The more dots/pixels the image contains, the sharper the image will print. As a result, printing will look blurry if a 72dpi image is used as compared to using a 300dpi high res image.
Sure you can. There are a few great resources for obtaining high resolution photos online. Many of our clients and our own graphic designers prefer istockphoto.com and jupiterimages.com. However, there are plenty more royalty free photo websites online which you can search for.
Often, you will require custom images pertaining to your own business or industry and you may have physical photos you would like to first scan then import into your design program. This is a perfectly acceptable method of acquiring high resolution images, just be sure to scan your photos in high resolution to begin with. All scanning software allows you to specify the resolution of image you would like to scan. Selecting 300dpi (or higher) as your scanning resolution will provide you with an excellent quality image for printing purposes.
Importing Images from a Digital Camera:
Many graphic designers use images from a digital camera such as the example catalog image to the right. This organization needed images specific to their facility so a digital camera was the best choice. There is really only one thing you need to know to ensure you are using a high resolution image. The only real difference between a high and low resolution image is the amount of pixels/dots (DPI) that are used to create the image. With this in mind, the high mega pixel camera you have taking the picture, the higher resolution the photos will be. Most cameras that can take photos above 3 mega pixels should be more than adequate to provide you with high resolution images. Keep in mind that you must have your camera set to the highest possible resolution when capturing your images.
All artwork design programs allow you to resize an image you are working on, but it's important to understand why simply resizing a low resolution image will not produce a true high resolution image. When you resize and make a low resolution image larger to meet the commercial printing specifications of 300DPI, all you are really doing is stretching the image. The technical term is called either resampling or interpolation. Since high resolution images are based upon the number of pixels an image contains, resizing will not create new pixels, information of your images and will only make each pixel larger by stretching it. The only way to ensure picture perfect high quality printing of your photos and images is to start with a high resolution image obtainable by the methods mentioned above.