27  5,460,919  28  EXAMPLE  10  EXAMPLE  9  As is clear from the  results shown in Table  21, according  to the  image-forming process  of this invention, even  when  the silver bromide  emulsion is used, the  high sensitivity and  high contrast occur  as in Test No. 36 and  good images can  be obtained.  Furthermore,  in Test No. 37 wherein  the amino  compound is added  to the developer and  Test No. 38 wherein  the compound having  an acidic  dissociation constant  pKa of  lower than 11 is added  to the film,  high-contrast images  can  be stably and more  rapidly formed over  a wide  developing  time. Moreover, in  Test Nos. 39 to 43  wherein after image- wise exposing, the  film containing the  compound having  a  negative reduction  potential and the compound  having an  acidic dissociation  constant pKa of lower  than 11 was  As is clear from the  results shown in Table  19, it can be  In Table 19, the relative  sensitivity is the relative  value of  the reciprocal of  the exposure time  giving density 3.0  excluding fog to each  sample with the sensitivity  of the film  sample developed with  Developer 31 for  5 minutes at 30°  C.  being defined as 100.  The gamma is the mean  slope between  densities 0.5 and 3.0  excluding fog, and  the fog is the density  at the unexposed area.  t,1370  The photographic  characteristics obtained  are shown in  Table 19. As the photographic  performance  in Table 19, the  developing time necessary  for giving the maximum  density  3.0 to each sample  is shown by a 15  second unit and the  photographic performance  at the case is shown.  Also, the  value when the developing  time is 5 minutes is  shown.  As the same as in  Example 9, the values  when the  developing time required  to give density 3.0  excluding fog  from the initiation  of the  development  was shown by a 15  second unit and the  values at the developing  time of 5  minutes. The relative  sensitivity was the relative  value of the  reciprocal of the exposure  amount giving density  3.0 exclud› ing fog with the sensitivity  of Film No. 59 of this  invention  in Test No. 37 developed  with Developer 29  for 2 minutes  at 30°  C. being defined as  100.  The photographic  characteristics obtained  are shown in  Table 21.  t,1400  After exposing the film  sample thus prepared  to a tungsten  lamp of 2666°  K.  using an LB-200  filter through a step  wedge having a step  difference of 0.15  for 5 seconds, the  sample was developed  with each of Developers  31 to 35  formed by adding each  of the compounds shown  in Table 18  below to Developer  18 in Example 7 containing  Metol as an  arninophenol developing  agent and ascorbic  acid (1-1) as the  reductone, stopped,  fixed, washed, and  dried. In the devel› oping condition, the  developing time was  changed from 30  seconds to 5 minutes  at 30°  C. wherein the change  of the  photographic characteristics  with the change of  the devel› oping time were determined.  t,1360  Each of Film Samples  59 to 65 was exposed  as in  Example 2, developed  with each of Developers  18 and 29 in  Example 7 and Developers  31 to 35 in Example  9 for a time  of from 30 seconds  to 5 minutes at 30°  C.  stopped fixed  washed, and dried.  The coated amount  of the added compound  was measured  by the same manner  as in Example 8.  t,1390  Before and after coating  the protective layer,  the coating  amount of the protective  layer was measured  and the addi› tion amount of  5-sulfosalicylic  acid per mo! of the  coated  silver amount was  calculated.  After adding 8x10- 3  mo! of  6-hydroxy-4-methyl-1,3,3a,  7-tetraazaindene  and 8x10- 3  mol of the pyridinium  salt  derivative (N-22:  reduction potential  -1.15 volt) to the  chemically ripened  silver chlorobromide  emulsion obtained  as in Example 2, the  emufsion was coated  on  polyethylene  terephthalate base  at a silver coverage  of 40 mg/dm 2 •  On the  emulsion layer was  coated a gelatin protective  layer con› taining 83 mmols of  5-sulfosalicylic  acid (pKa: 2.5, 12.0  in  water of 25° C.)  per mo! of silver  halide together with  formaldehyde  and  methylolurea  as hardening agents.  By  simultaneously adding  an aqueous silver nitrate  solu› tion and an aqueous  potassium bromide  solution containing  3.0x10- 7  mo! of sodium  hexabromorhodate(III)  per mo! of  silver to an aqueous  gelatin solution kept  at 60°  C. while  keeping pAg at 7.0  over a period of 60  minutes, a mono› dispersed silver bromide  emulsion containing  the cubic  crystal silver halide  grains having a mean  grain size of 0.22  µm  was prepared. After  removing soluble salts  by an ordi- nary method, 25x10- $^{5 }$mo! of sodium thiosulfate  per mo! of  silver halide was added  to the emulsion and  the emulsion  was subjected to chemical  ripening for 70 minutes  at 60°  C.  After adding 12xl0- $^{3 }$mo! of  6-hydroxy-4-methyl-1,3,3a,  7- tetraazaindene  and 8x10- $^{3 }$mo! of the pyridinium  derivative  (N-28: reduction potential  -0.80 volt) per mo!  of silver  bromide to the foregoing  silver bromide emulsion,  the  emulsion was coated  on a  polyethylene terephthalate  base at  a silver coverage of  40 mg/dm 2 •  On the emulsion layer  was  coated a gelatin layer  containing each of  the compounds  having an acidic dissociation  constant pKa of lower  than 11  for use in this invention  shown in Table 20  together with  formaldehyde  and  dimethylolurea  as hardening agents  fol- lowed by drying to  provide Film Samples  59 to 65.  As described above,  it can be seen that  by using the film  containing the compound  having a negative reduction  poten- tial and the compound  having an acidic dissociation  constant  pKa of lower than  11, images can be  formed under more  preferred practical  developing conditions.  As is clear from the  results shown in Table  17, in the case  of developing Film  Sample Nos. 47 to  58 containing the  compound having  a negative reduction  potential and the  compound having  an acidic  dissociation constant  pKa of  lower than 11 with  Developer 18, super  high-contrast  images having a gamma  of 15 or higher are  obtained with a  more rapid developing  time and also the good  super high› contrast images are  stably obtained with  wider developing  times.  In Table 17, the relative  sensitivity is the relative  value of  the reciprocal of the  exposure amount  giving density 3.0  excluding fog to each  sample with the sensitivity  of the  sample of Film Sample  No. 56 developed  for 1 minute and  45 seconds at 30°  C. being defined as  100. The gamma is  shown by the mean  slope between densities  0.5 and 3.0  excluding fog, the  fog is the density at  the unexposed area,  and Dmax is the maximum  density of the film  excluding fog.  t,1340  seen that according  to the  image-forming process  of the  present invention  of developing the  silver halide photo› graphic material of  this invention containing  the compound  having a negative  reduction potential  and the compound  having an acidic dissociation  constant pKa of lower  than 11  with the developer  containing the aminophenol  derivative  developing agent,  the reductone, and  the amino compound  for use in this invention,  good super high-contrast  images  are formed more preferably,  more rapidly and  stably for  developing time between  one minute to 5 minutes  at 30°  C. 