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 

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. 

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. 

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. 

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 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 

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. 

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 

As is clear from the results shown in Table 19, it can be 

## EXAMPLE 9 

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. 

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. 

The coated amount of the added compound was measured by the same manner as in Example 8. t,1390 

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 photographic characteristics obtained are shown in Table 21. t,1400 

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. 

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 

## EXAMPLE 10 

