3. Fix-dark or appropriate safelight 4.  Wash-white  light 5.  Dry-white  light In addition to exposure, there are four factors in development that control image density, contrast, and, to  a  limited  degree,  the  uniformity  of  individual densities in a negative. These four factors are the type of developer used, development time, temperature of the developer,  and  agitation  as  follows: Type of developer. One type of developer cannot cover all film exposure/processing situations. For example, film exposed under poor lighting conditions may require a vigorous developer to bring out as much image detail as possible, while film exposed under normal conditions requires a normal working developer. There  are  many  different  developers,  each  provides  a different activity and quality of development. The actual choice of the developer to use depends on the following: the type of film, conditions under which it was exposed, type of negative required, developing time that is best for the method of development to be used, and the manufacturer’s recommendation. Time and temperature. Many factors must be considered if you want to ensure correct development during film processing. Two of these factors are the length of time the film is allowed to develop and the temperature of the developer solution. Both factors can have a significant impact on the quality of the processed film. 10-15 The normal temperature for hand processing most black-and -white film is 68°F (T-Max film with T-Max developer is 75°F). There are several reasons for this standardization. At a temperature of 68°F, the gelatin swells sufficiently to allow adequate penetration of the developing solution without oversoftening to the point where it is easily damaged (which occurs at higher temperatures). Temperatures lower than 68°F slow development  excessively.  Only  when  time  is  of  the utmost  importance  are  accelerated  temperatures  used.  In most instances when high temperatures are used, the film is treated in a hardening bath before processing, or the film is designed specifically for being processed at such temperatures. Since a rise of several degrees in temperature shortens development only a small amount, there is little to be gained by deviating from standard processing   temperatures. As  explained  earlier,  the  activity  of  a  developer increases   as   its   temperature   increases.   Film development carried out for a given time at a given temperature produces both predictable and desired results-assuming, of course, that the film has been exposed properly. When film is developed for a given time at a given temperature, it is called "time and temperature development." When   you   know   the   time   and   temperature relationship for a given film and developer combination, processing in total darkness becomes simple. You simply adjust solutions to the prescribed temperature and  then  process  the  film  for  the  required  time. Assuming proper exposure, time and temperature processing can produce a correctly developed negative without your having to see what is happening in the solution. In  the  time  and  temperature  method  of  film processing, as in any method of film processing, if the film is developed for too short a time or at too low a temperature,  a  weak,  low-contrast  image  results. Underdevelopment can result in insufficient highlight density. On the other hand, if the negative is developed for too long a period or at too high a temperature, the result is a negative having too much density. The developer solution overdevelops the exposed areas and may even develop some of the unexposed silver halides. All solution temperatures (developer, rinse, fix, and wash) should be as close to each other as possible. When there is considerable difference in the temperature of the solutions, excessive graininess may result, or the emulsion may be subject to excessive expansion and contraction that causes it to wrinkle or crack This effect is called reticulation. Since reticulation is not correct- able, it causes the negative to be useless for printing. For correct development, both time and temperature must be accurately controlled. Within limits, time can The temperature of solutions may be adjusted by surrounding them with hot water, cold water, or ice. Never add water or ice directly to a solution because it dilutes the developer to an unknown degree. Ice may be placed in a container and suspended in the solution. An immersion heater may be used in the solution to raise its temperature. be  adjusted  for  a  given  temperature,  or  temperature  can be adjusted for a given time. There is a definite correlation between time and temperature.  When  it  is  impossible  to  maintain  solution temperature at the desired level, time can be shortened or lengthened to compensate. As the temperature increases, developing time must be decreased to provide equivalent development. As the temperature decreases, development  time  must  be  increased.