diff --git a/backend/genesys.c b/backend/genesys.c
index 2d80bf025..5a1685d07 100644
--- a/backend/genesys.c
+++ b/backend/genesys.c
@@ -1547,7 +1547,7 @@ sanei_genesys_init_shading_data (Genesys_Device * dev, int pixels_per_line)
   int channels;
   int i;
 
-  if(dev->model->ccd_type==CCD_KVSS080)
+  if(dev->model->ccd_type==CCD_KVSS080 || dev->model->ccd_type==CCD_G4050)
     return SANE_STATUS_GOOD;
 
   DBG (DBG_proc, "sanei_genesys_init_shading_data (pixels_per_line = %d)\n",
@@ -2590,7 +2590,7 @@ genesys_dummy_dark_shading (Genesys_Device * dev)
       skip = 4;
       xend = 68;
     }
-  if(dev->model->ccd_type==CCD_KVSS080)
+  if(dev->model->ccd_type==CCD_G4050 || dev->model->ccd_type==CCD_KVSS080)
     {
       skip = 2;
       xend = dev->sensor.black_pixels;
@@ -3533,6 +3533,7 @@ genesys_send_shading_coefficient (Genesys_Device * dev)
                             target_code);
       break;
     case CCD_KVSS080:
+    case CCD_G4050:
       target_code = 0xe000;
       free(shading_data);
       length=compute_gl843_coefficients (dev,
diff --git a/backend/genesys_devices.c b/backend/genesys_devices.c
index 0cbfab711..2ebf7c68b 100644
--- a/backend/genesys_devices.c
+++ b/backend/genesys_devices.c
@@ -486,11 +486,11 @@ static Genesys_Sensor Sensor[] = {
    NULL, NULL, NULL}
   ,
   {CCD_G4050,
-   600, /* XXX STEF XXX 4800 */
+   1200, /* XXX STEF XXX 4800 */
    48,
    28,
    152,
-   2698*2, /* XXX STEF XXX 42574 */
+   10200, /* XXX STEF XXX 42574 */
    210,
    230,
    /* 08    09    0a    0b */
@@ -1054,8 +1054,8 @@ static Genesys_Model hpg4050_model = {
   GENESYS_GL843,
   NULL,
 
-  { 600, 300, 200, 150, 75, 0},	/* possible x-resolutions */
-  { 600, 300, 200, 150, 75, 0},	/* possible y-resolutions */
+  { 1200, 600, 300, 200, 150, 75, 0},	/* possible x-resolutions */
+  { 1200, 600, 300, 200, 150, 75, 0},	/* possible y-resolutions */
   {16, 8, 0},			/* possible depths in gray mode */
   {16, 8, 0},			/* possible depths in color mode */
 
@@ -1089,9 +1089,10 @@ static Genesys_Model hpg4050_model = {
   DAC_G4050,
   GPO_G4050,
   MOTOR_G4050,
+  GENESYS_FLAG_NO_CALIBRATION |
   GENESYS_FLAG_LAZY_INIT | 	/* Which flags are needed for this scanner? */
   GENESYS_FLAG_SKIP_WARMUP | 
-  GENESYS_FLAG_NO_CALIBRATION |
+  GENESYS_FLAG_OFFSET_CALIBRATION |
   GENESYS_FLAG_CUSTOM_GAMMA,
   GENESYS_HAS_SCAN_SW | GENESYS_HAS_FILE_SW | GENESYS_HAS_COPY_SW,
   280,
diff --git a/backend/genesys_gl843.c b/backend/genesys_gl843.c
index 1f7ca3e91..62b7910d7 100644
--- a/backend/genesys_gl843.c
+++ b/backend/genesys_gl843.c
@@ -524,18 +524,20 @@ gl843_setup_sensor (Genesys_Device * dev, Genesys_Register_Set * regs, int dpi)
 
   /* use x1 cksel when at higher resolutions */
   /* KV-SS080 sensor */
-  if(dpi>dev->sensor.optical_res/2)
+  if (dev->model->ccd_type == CCD_KVSS080)
     {
-      r = sanei_genesys_get_address (regs, 0x18);
-      r->value &= ~REG18_CKSEL;
+      if(dpi>dev->sensor.optical_res/2)
+        {
+          r = sanei_genesys_get_address (regs, 0x18);
+          r->value &= ~REG18_CKSEL;
 
-      sanei_genesys_write_register (dev, 0x78, 0x03);
+          sanei_genesys_write_register (dev, 0x78, 0x03);
+        }
+      else
+        {
+          sanei_genesys_write_register (dev, 0x78, 0x07);
+        }
     }
-  else
-    {
-      sanei_genesys_write_register (dev, 0x78, 0x07);
-    }
-
 
   for (i = 0; i < 9; i++)
     {
@@ -650,9 +652,6 @@ gl843_init_registers (Genesys_Device * dev)
   SETREG (0x71, 0x03);
   SETREG (0x72, 0x04);
   SETREG (0x73, 0x05);
-  SETREG (0x74, 0x00);
-  SETREG (0x75, 0x00);
-  SETREG (0x76, 0x00);
   SETREG (0x7d, 0x00);
   SETREG (0x7f, 0x00);
   SETREG (0x80, 0x00);
@@ -672,24 +671,29 @@ gl843_init_registers (Genesys_Device * dev)
     {
       SETREG (0x03, 0x1d);
       SETREG (0x05, 0x08);
+      SETREG (0x06, 0xd0); /* SCANMOD=110, PWRBIT and no GAIN4 */
       SETREG (0x0a, 0x18);
       SETREG (0x0b, 0x69);
       SETREG (0x5e, 0x6f);
+      SETREG (0x6b, 0xf4);
 
-      SETREG (0x80, 0x00);	/* XXX STEF XXX 5a/50 */
-      SETREG (0xab, 0x40);
       SETREG (0x70, 0x00);
       SETREG (0x71, 0x02);
       SETREG (0x72, 0x00);
       SETREG (0x73, 0x00);
       SETREG (0x7d, 0x90);
-      SETREG (0x7e, 0x01);
+      
+      SETREG (0x80, 0x50);
+      SETREG (0x9d, 0x08);
+      SETREG (0xab, 0x40);
 
       /* XXX STEF XXX TODO move to set for scan */
       SETREG (0x98, 0x03);
       SETREG (0x99, 0x30);
       SETREG (0x9a, 0x01);
       SETREG (0x9b, 0x80);
+      
+      SETREG (0xac, 0x00);
     }
 
   /* fine tune upon device description */
@@ -2147,10 +2151,23 @@ gl843_begin_scan (Genesys_Device * dev, Genesys_Register_Set * reg,
 
   /* set up GPIO for scan */
   /* KV case */
-  RIE (sanei_genesys_write_register (dev, REGA9, 0x00));
-  RIE (sanei_genesys_write_register (dev, REGA6, 0xf6));
-  /* blinking led */
-  RIE(sanei_genesys_write_register(dev,0x7e,0x04)); 
+  if (dev->model->gpo_type == GPO_KVSS080)
+    {
+      RIE (sanei_genesys_write_register (dev, REGA9, 0x00));
+      RIE (sanei_genesys_write_register (dev, REGA6, 0xf6));
+      /* blinking led */
+      RIE(sanei_genesys_write_register(dev,0x7e,0x04)); 
+    }
+  if (dev->model->gpo_type == GPO_G4050)
+    {
+      RIE (sanei_genesys_write_register (dev, REGA6, 0x44));
+      RIE (sanei_genesys_write_register (dev, REGA7, 0xfe));
+      RIE (sanei_genesys_write_register (dev, REGA8, 0x3e));
+      RIE (sanei_genesys_write_register (dev, REGA9, 0x06));
+      /* blinking led */
+      RIE(sanei_genesys_write_register(dev,0x7e,0x01)); 
+    }
+
   
   /* clear scan and feed count */
   RIE (sanei_genesys_write_register (dev, REG0D, REG0D_CLRLNCNT | REG0D_CLRMCNT));
@@ -3498,6 +3515,10 @@ gl843_cold_boot (Genesys_Device * dev)
     }
   else
     {
+      /* CK1MAP */
+      RIE (sanei_genesys_write_register (dev, 0x74, 0x00));
+      RIE (sanei_genesys_write_register (dev, 0x75, 0x00));
+      RIE (sanei_genesys_write_register (dev, 0x76, 0x00));
       /* CK3MAP */
       RIE (sanei_genesys_write_register (dev, 0x77, 0x00));
       RIE (sanei_genesys_write_register (dev, 0x78, 0x07));
diff --git a/backend/genesys_gl843.h b/backend/genesys_gl843.h
index fe67c1484..b27d4a482 100644
--- a/backend/genesys_gl843.h
+++ b/backend/genesys_gl843.h
@@ -327,6 +327,7 @@
 
 #define REGA6   	0xa6
 #define REGA7 		0xa7
+#define REGA8 		0xa8
 #define REGA9 		0xa9
 
 #define SCAN_TABLE 	0 	/* table 1 at 0x4000 */