Silver halide emulsion, method of preparing the same, and silver halide color photographic photosensitive material and image-forming method using the emulsion

A method of preparing a composition for use in image formation, the method comprising the steps of:

• (a) preparing a silver halide emulsion including silver chloride of at least 90 mol % by content;
• (b) adding an oxidatively dimerized form of a mesoionic compound comprising a thiolate structure to the emulsion, the oxidatively dimerized form of a mesoionic compound having a thiolate structure represented by the following formula:
• wherein in the formula, f represents a sulfur atom, e represents a carbon atom, and a, b, c, and d are each an unsubstituted or substituted atom constituting an aromatic 5-membered heterocycle having a positive charge and each independently represents a C—R group, an N—R′ group, an oxygen atom, or a sulfur atom, where R and R′ each independently represents a hydrogen atom or a substituent;
• and
• (c) carrying out gold sensitization,
• wherein step (b) and step (c) may be carried out simultaneously or in inverse order.