1. Improper file preparation can lead to costly reprints. The most common problem affecting image quality is insufficient camera settings. Review instructions for your particular camera to determine how to obtain the highest resolution images. Out of focus pictures, with too little pixel resolution and poor lighting do not make great large posters.
Megapixels are used as a selling feature but most consumers complain when memory is quickly consumed or if photos are too large to email. So camera manufacturers typically set a lower default resolution. The result? Images look good small and that is how they should remain. If you plan on printing great looking large images, increase the resolution before taking pictures and utilize the maximum quality setting.
2. The second common problem is related. Many people are now familar with the JPEG image format. It is the default for most digital cameras and offers varying levels of quality. JPEG includes compression achieved by averaging colors. At small sizes, it may not be noticeable. However, when enlarged, banding or halos around edges (called artifacts) are more visible. Special smoothing techniques can be applied to minimize artifacts. However, if any edits are made, do not save the image as JPEG again. This results in more averaging of saved colors with inherent image degradation. Save edited JPEG images as TIFF. If you have JPEG images and are uncertain how to minimize artifacts, files can be submitted in their original form, requesting enhancement by Reactive Imaging.
3. The third common problem degrades output quality. Do not include images intended for the Web on printed posters. Resolution of GIF or JPEG images are usually just 72 ppi and very small. Further they may have considerable compression for fast page display. This means noticeable artifacts are apparent when enlarged.
4. The fourth common problem causes output anomalies even when the PDF appears normal. Page layout programs allow the combination of RGB, CMYK, and spot colors such as Pantone in one document. It is generally best to decide upon one color space - either RBG or CMYK - especially when colors are blended or transparency effects such as drop shadows or multiplied colors are used. When such effects are used in combination with spot Pantone colors, convert them to CMYK without editing the original formula.