Ricoh MPC7501
Troubleshooting. Correcting the Halo Effect
Images printed with the GW controller may show a "halo" effect when printing in 2-bit mode (1800x600dpi) and in 4-bit mode (9600x600dpi).
Problem
- This problem is most visible when text is overlaid onto halftone areas in 2-bit mode or 4-bit mode. The greater the difference in image density between text and halftone areas, the more noticeable the halo effect.
- This problem is also evident when the mode is changed to 2-bit mode. (The default dithering pattern for 2-bit mode is designed to improve gradation, but this can also make the halo effect more visible.)
- This problem is a product limitation for this model, as announced in the SLG (User/Sales/Service Remarks #12).
Solutio
The following solution is only effective when using the GW controller. There are two ways to reduce the halo effect:
- Print out the image using 1-bit mode (600x600dpi) instead, or
- Change the dither pattern used in 2-bit mode (1800x600dpi). As mentioned above, the default dither pattern for 2-bit mode is provided to improve gradation. However, there is one more dither pattern (“Low halo effect dither”) that can be selected to reduce the halo effect.
Procedure: To Change the Dither Pattern for 2-Bit Mode
Do the following procedure manually to change the dither pattern used in 2-bit mode to “Low halo effect dither”.
- Confirm that the Printer/Scanner firmware is Ver1.00.1 (D3765902A) or newer.
- Execute SP5801-008 (Memory Clear Printer Application). When you execute this SP, the following will be reset to factory settings:
• The gamma curve adjusted at the last Printer ACC execution.
• All Group SP1000 settings in Printer SP mode, which includes SP1104 (Gamma Adjustment) and SP1106 (Toner Limit). - When you see the “Completed. You have to reboot.” message, turn the machine on.
- Open Printer SP1001-002 (Bit Switch – Bit Switch 2 Settings).
- Touch the “6” key, and then the [#] key on the operation panel. The LCD display will change:
Before (default): 00000000 (0) [00H]
After (Low Halo Effect Dither): 01000000 (0) [40H] - Exit Printer SP mode, and then turn the main power switch OFF and ON.
- Execute Printer ACC using Test Pattern 2 (1800X600dpi).
Now, when the user selects 2-bit mode (1800x600dpi) in the printer driver, the Low Halo Effect
Dither function will be applied automatically.
Procedure: To Restore the Default
To change the dither pattern for 2-bit mode back to the default pattern, do this procedure.
- Execute SP5801-008 (Memory Clear Printer Application).
- Cycle the machine off/on.