Image resolution – actual and effective
Great image resolution – actual and effective.
Great image resolution is what everyone wants. But, what is the difference between actual and effective?
Effective resolution is sometimes puzzling to self-publishers and designers. Book printing requires resolution at 300 ppi or larger, and the photograph or image needs to be at the size it will be when printing in the book. This is where effective resolution comes into play.
- Actual resolution is the resolution of a photograph or image at 100%.
- Effective resolution is the resolution after the image is enlarged or reduced. The effective resolution is what counts.
Images for the Web
| Resolution: | 72 to 96 ppi |
| Color mode: | RGB |
| Format: | JPG or PNG |
Images for Book Printing
Book printing uses a resolution of 300 ppi or larger in a JPG or TIF format. They must be at the dimensions they will be when printed in the book, or larger.
| Resolution: | 300 ppi |
| Color mode: | CMYK or other Pantone libraries. |
| Example: | Pantone + Color Bridge Coated for coated stock. |
| Example: | Pantone + Color Bridge Uncoated for uncoated stock. |
| Example: | CMYK if you are picking a color out of a photograph with the eyedropper tool. |
| Format: | JPG or TIF |
EXAMPLE OF ADJUSTING FOR EFFECTIVE RESOLUTION
Let’s suppose that all your photos are 72 ppi, but they are a whopping 32 inches wide. This is where a little bit of math comes in, or just place the image in InDesign. Go to Links and highlight an image.
Watch the Effective Resolution increase as you reduce the image to the page width, or smaller.
There is no substitution for the original scan or a high-resolution photo. A low-res image may look sharp on your monitor, because everything looks good on a monitor that only needs 72 ppi. However, this low-resolution image will not print well. It will be pixelated.
