For designing digital files intended for offset printing, it’s essential that all of the images and photographs in your files are of high resolution, ensuring you a high quality print-job.
Probably you have seen printed brochures or other printed marketing material that contain blurry or blocky images? This always provides a bad presentation and most likely is caused by embedding low resolution images. The information below covers the specific topic of resolution for print design and how to avoid problems.
Definition of (Image) Resolution
There are different types of resolution: Print resolution (e.g. image resolution) and monitor resolution (e.g. display resolution) are two different environments. In this article we’re concentrating on the topic of image resolutions (print design), we’ll begin with throwing in the definition of resolution:
Resolution is the term used to describe the number of dots used to display an image .
The rich tones, colour and detail achieved in printed brochures are derived from high resolution photography and graphics. Higher resolutions mean that more pixels are used to create the image, resulting in a crisper, cleaner image. It’s really that simple.
What means D.P.I. and why is it so important?
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. If you are working with website files then they require a much lower resolution than an advertisment, catalog or a brochure.
In general graphics for web and online photos are normally created at 72dpi (dots per inch). This low resolution is just great for web design, cause the images look sharp on a computer screen and the digital file sizes (.jpg, .png or .gif) are very small which helps web pages to upload much faster.
However, when you are designing graphics for commercial printing purposes, your rasterized images (TIFF, .jpg, etc.) should be at least 300 dpi. These files can be rather large in file size.
One of the most common mistakes is embedding web graphics or online photos in your digital files intended for offset printing. As a result, printing will look blurry if a 72dpi image is used as compared to using a 300dpi high resolution image.
How and where can I get high resolution images?
There are some great and well-known resources for acquiring high resolution images online: istockphoto.com and vanbeekimages.com are just a few websites where you can purchase high resolution images. However, there are plenty more royalty free photo websites online which you can search for.
If you already have photos on paper, you could scan these photos and then import them into your Image Editing Program. This also is a perfectly acceptable method of obtaining high resolution images, just be certain 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.
Many graphic designers use images from a digital (pocket) camera or SLR-camera to embed in graphic digital files. 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.
If in doubt what the real resolution is of your picture, open the picture in Adobe Photoshop (or another professional Image Editing Program). SLR Cameras in the range of 10 MB are capable of printing out a high resolution image at 21 by 29,7 cm (A4 paper-size).
Note: save all photos in CMYK mode, not RGB mode when possible. Images saved in RGB mode may not print properly.
If Resizing isn’t the answer, what is ..?
Almost all Image Editing Programs allow you to resize an image, but it’s important to understand why simply resizing a low resolution image will not produce a true high resolution image. Since images are based upon the number of pixels they contain, resizing will not create new pixels, it will only make each pixel larger by stretching it.
There is also a very special technique for squeezing pixels into an image, but only use this technique for Extreme Large Format Printing (i.e., billboard) situations. When you increase the resolution the computer simply adds in more pixels by averaging out the information in the image. This only makes the file size larger but does not add in any more detail. The technical term is called either upsampling or interpolation.
Does this mean all photos of low-quality (96 dpi or less) are unsuitable for print? Not at all. You can increase the resolution of the image without messing with the number of pixels. Here’s how:
- In Adobe Photoshop, choose Image>Image Size.
- At the bottom of the dialog, uncheck Resample Image. This all-powerful magic option locks the number of pixels contained in the image, thereby locking the quality. Now enter 300 into the Resolution field.
The image is now 300 dpi and the physical size has decreased (4 times as small as the original size/dimension), the pixel information stayed the same. The exact same number of pixels as in the original image; they’re just packed more tightly together. Furthermore, notice how the file size didn’t change at all?
Admittedly, this could be quite confusing because the onscreen image didn’t change, .. pure magic? The truth is only revealed by the Image Size dialog. But it’s best to work with high-resolution originals, obtained like mentioned earlier.
The design process requires careful monitoring of specifications like colour control, ink application, registration, imposition, finishing etc. These are just a few of the areas of print design which need to be viewed in context with the overall job. High resolution printer’s proofs are still the best indication of colour integrity, and this is why it is vital for the designer to work closely with the printer to match the client’s expectations with the final printed piece as closely as possible.
 – resource: about.com
 – TIFF (TIF) files are excellent for any kind of photo or image because they maintain quality. Note: Save them with LZW compression and resolution 300dpi, which minimizes file size but does not degrade image quality (NO visible effect on the printed product).
 – Resampling or interpolation is the name for the process which figures out how best to subtract (or add) pixels when the number of pixels in the image is changed.
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That’s all folks, I hope this article has helped to clear up whatever resolution confusion you might have had. What is your experience with resolution for print design, please let me know. The comment-section is all yours ..!