Operation of ADC and MEtImage Adapt

The goal of ADC is to automatically and transparently reduce Memory Out errors caused by raster graphics pages. MEt extends this goal to reducing all Memory Out errors and eliminating Print Overrun errors.

During the printing of a page, if available printer memory becomes low, all HP LaserJet 4, 5, and 6 family printers and the HP Color LaserJet printer have the ability to automatically compress any already-stored raster graphics data using a variety of compression techniques. This allows the printing of many raster graphics pages which would have caused a Memory Out error on previous HP LaserJet printers having the same amount of memory.

With ADC or MEt, PCL 5 printers can typically print a full page of raster graphics in base memory without a memory out. This is especially true for line art and typical business graphics. Other types of graphics such as scanned photographs (especially if a technique called error-diffusion is used), cannot always be printed as easily by ADC or MEt as can line art graphics. Fortunately, another internal printer feature, Image Adapt, can be called upon to make the page fit in memory.

Image Adapt is only used as a last resort for compressing raster graphics data and as such will rarely be seen. It reduces a raster graphic image to one-fourth its original size by trading off some of the image’s fine detail. This loss of fine detail is often not noticeable.

Image Adapt can be disabled on some of the HP LaserJet 4, 5, and 6 family printers if required, but the technique varies. On the HP LaserJet 4, 4M and 4Si the user will have to add more memory to effectively remove the need for Image Adapt. Image Adapt can be disabled on some of the other HP LaserJet 4, 5, and 6 family printers by using a PJL command (refer to the respective printer user manuals for further information—the Color LaserJet printer does not utilize Image Adapt). If Image Adapt is turned off, more pages will cause Memory Out errors.

5-2 Memory Usage