Lane Press’s technical documentation specifies that “CMYK and grayscale images should have an effective resolution of 300dpi.” Although we refer to this industry-wide benchmark as a standard for successful image reproduction, achieving it is not always possible. For example: You have a supplied image to work with and a designated space in your layout to place it. If you are required to resize the image to make it fit this space, achieving 300dpi may not be possible. Here is a primer on image resolution, including some general guidance for working with images in less-than-ideal situations.

 

Let's start by defining the term "Effective Resolution." This refers to image resolution subsequent to scaling. The action of scaling images up or down in size when you place them in a layout has an effect on the quality of the image. Specifically, it alters the resolution for printing purposes in inverse proportion to the amount it is scaled. For example, scaling a 300dpi image up to 200% decreases the effective resolution to 150dpi. When you take an optimized image and make it larger, the quality degrades.

Here's the formula for calculating effective resolution:

Actual Resolution / scale (percentage x .01) = effective resolution

The recommended image resolution for a publication printing at a line screen of 150lpi (the standard line screen for most magazines) should be 300dpi. This will give you the best possible quality reproduction. Below this benchmark, image quality starts to degrade on a slow curve. Having said that, the casual reader is not likely to discern the difference in quality with some types of images until the resolution drops below 225. The variables that affect the point at which this degradation occurs include overall quality of the image (sharpness of detail, graininess), subject matter (close-up vs. landscape), the presence of sharply contrasting color edges, and the presence of rasterized type.

 

How can you determine whether an image with less-than-ideal resolution will print well?  Consider the type of image and your intended usage. For example, an image that is a grayscale or a duotone, or one with a background image that is screened back (not opaque), will typically produce well at a lower resolution. This is especially true for landscapes and other distance shots, which are relatively forgiving. Resolution is more critical for grayscale and duotone images of nearby objects or portrait close-ups, which have crisp detail. For these types of images, you want to make sure you have achieved a full 300dpi resolution in order to ensure the best reproduction in print.

 

If you are having trouble optimizing an image and would like help determining whether an image will reproduce well in print, please contact your Customer Service Representative, who will direct you to the most appropriate technical resource.