Processing

After a photographic emulsion has been exposed, it must be processed for the image to appear and remain stable. Processing means putting the emulsion through a series of chemical baths called developer, stop bath, and fixer. The chemistry and procedures are essentially the same for processing film and paper. The main difference is that film processing must be done in complete darkness to prevent the film from becoming fogged. Print processing can be done under a red-filtered light called a safelight. You should read the instructions supplied with all chemicals before using them.

Step 1 - Developer

Before an exposed emulsion has been processed, there is no noticeable change in its appearance. At this point, the negative is said to contain a "latent image." The developer chemically converts this latent image to the visible silver image that makes up the negative and print. Remember that the longer the emulsion is left in the developer, the more dense these deposits of silver will be. If film is left in the developer for too long, these deposits of silver will become so dense that they will block too much of the light from the enlarger, and the print will be too white and contrasty. This effect is called overdevelopment. If a negative is underdeveloped, areas of the print that should be white will instead be gray, and the print will be dark and muddy. Prints that are under- or overdeveloped will either be too light or too dark, respectively. For this reason, the development stage of the process must be timed carefully. As you will learn from this book, the correct development time for film depends on the contrast of the subject. The standard development time for most photographic paper is from two to four minutes. For more information on developers, refer to Appendices E, G, and J.

Step 2 - Stop Bath

Because the timing of the development stage of the process is so critical, it is important that the emulsion stop developing as soon as the proper density has been reached. Developers must be alkaline to work. Because stop baths are acidic, immersing films or papers in a stop-bath solution will stop the developing process immediately. A 15- to 30-second rinse in fresh stop bath is sufficient.

The fixing bath dissolves the remaining unexposed silver in the emulsion and allows it to be washed away. It is important that the fixing stage of the process be complete because any residues of unexposed silver will eventually stain the film or print and ruin the image. If your fixer is fresh and properly diluted, the minimum time that you should fix your negatives and prints before turning on the white light is two minutes for negatives and one minute for prints. Certain rapid fixers reduce the time required for complete fixing. Be sure that you read the manufacturer's instructions very carefully for proper dilutions and times.

Step 4 - Washing

After your negatives or prints have been processed, they must be thoroughly washed in clean water to remove any traces of fixer from the emulsion. The use of a hypo clearing agent will greatly reduce the amount of washing time necessary to do a good job. Once again, carefully follow the manufacturer's instructions. Improperly washed negatives and prints will become stained.

Step 5 - Drying

Many photographers take drying for granted, but it's easy to ruin a good negative or print at this point. A wet emulsion is very soft and can be scratched or attract dust if you aren't careful.

Even more serious are the uneven densities that can form in negatives because of drops of water drying on the surface of your film. To avoid this you should always use a wetting agent in your final rinse to prevent spotting. This isn't necessary when drying prints. Be sure to dry your negatives and prints in a clean, dust-free area.

Efficient processing is essential for getting good results in your photography. There is nothing more frustrating than spoiling a good negative by being sloppy or careless. Particular attention should be paid to the following points:

1. Cleanliness. Many unnecessary negative and print defects are caused by not washing your hands, tanks, trays, and reels carefully. Traces of fixer or developer on your fingers can easily leave stains on your prints that can't be removed. Keep in mind that even a soiled towel or a contaminated light switch can transfer chemicals to your hands if you aren't careful.The first time you discover a thumbprint etched into your favorite negative, you will appreciate the importance of being careful and clean.

2. Agitation. Agitation means causing your photo-chemistry to circulate and flow around the film or paper by keeping the development tank or printing tray in motion for a given amount of time during each stage of the process. This is necessary for the development and fixing of the emulsion to be even and complete. Film agitation is usually done by inverting and rotating the tank in a continuous and rhythmic twisting motion. The proper film agitation motion is infinitely easier to demonstrate than describe. One manual recommends that you use a "quasi-spiral torus motion." I would suggest that you find a friendly camera salesperson or photographer and ask him or her to show you how it's done. You might want to check the salesperson's negatives and prints to see whether he has trouble with development streaks or air bubbles.

Correct agitation is especially important during the development stage of the process. If the motion you use fails to circulate the developer evenly around your film, your negative will have areas of uneven density that will show in your prints. Jerky or consistently violent agitation movements can create bubbles in the developer that can stick to your film and cause spots. To dislodge any of these bubbles, you should rap your tank against a hard surface after each agitation. Perhaps the most important thing to remember about agitation is that the longer and more aggressively you agitate, the faster your film will develop. For this reason, it is important that you establish a definite plan for your agitation and follow it religiously. This is especially important during the development and fixing stages of the process. A typical agitation plan would be:

• For developments from 3 to 4 minutes — Agitate continuously.

• For developments from 4 to 15 minutes — Agitate for 30 seconds, rest for 30 seconds, then agitate for 5 seconds of every 30 seconds thereafter.

• For developments longer than 15 minutes — Agitate continuously for 1 minute, rest for the next minute, then agitate for 30 seconds of every 2 minutes thereafter.

3. Temperature. It is very important that you adjust the temperature of the processing solutions before you begin using them. The cooler photo-chemicals become, the less efficient they are. Conversely, the warmer your chemicals are, the faster they will work. Most photo-chemicals are formulated to work at 68 degrees. If for some reason you have to use your chemistry at a higher or lower temperature, consult a time and temperature conversion chart for the correct development time at a given temperature. These are usually provided with your developer.

It is also very important that the temperature of all your chemicals is the same. This includes the water you use to wash your negatives and prints. A more than 1- or 2-degree variation in the temperature of your chemicals can seriously damage the quality of your negatives.

4. Dilution. Carefully follow the manufacturer's mixing instructions for all your photochemistry. Inconsistent dilution of your chemistry will make it impossible for you to control or standardize your processing results. Developer or fixing solutions that are either too dilute or too concentrated will drastically affect the amount of time it takes to produce the best results. The rule is: The more concentrated the developer and fixer, the faster they will work. Of course, the reverse is also true. The more dilute the photo-chemistry, the longer your processing time will be. For more information about dilutions, refer to Appendix J.

As you can see, agitation, temperature, and dilution are processing variables that must be carefully controlled to give your photographic work the consistency you need. When you become more experienced, you will discover that there are advantages to modifying all these controls, but in the initial stages, it's a good idea to consider development time the only variable that you can reliably control.

Film Processing

Step 1:	Development	3 to 30 minutes
Step 2:	Stop bath	30 seconds
Step 3:	Fixer	5 minutes (check instructions)
Step 4:	Rinse	2 minutes
Step 5:	Hypo clear	3 minutes
Step 6:	Final wash	15 minutes
Step 7:	Wetting agent	1 minute
Step 8:	Dry

Note: The exact development times for film will vary greatly according to a number of factors, including the film you are using, the developer and dilution, and most important, the contrast of the scene being photographed. This subject is covered thoroughly in Chapter 6.

Note: The exact development times for film will vary greatly according to a number of factors, including the film you are using, the developer and dilution, and most important, the contrast of the scene being photographed. This subject is covered thoroughly in Chapter 6.

Print Processing

Step 1:	Development	2 to 4 minutes
Step 2:	Stop bath	30 seconds
Step 3:	Fixer	5 minutes
Step 4:	Wash	2 minutes
Step 5:	Hypo clear	2 minutes
Step 6:	Final wash	1 hour (archival)
Step 7:	Dry

By altering the size and composition of the silver grains in the emulsion, films can be made more or less sensitive to light. The more sensitive an emulsion is, the less light it takes to produce a given density. Very sensitive films are said to be faster than films that are less sensitive because they allow you to use a faster shutter speed in a given lighting situation. Films of various speeds are assigned numbers by the American Standards Association. These are called ASA numbers. The important thing to remember about ASA numbers is that the higher the film's ASA number, the faster the film. Thus a film rated ASA 400 is more sensitive to light than a film rated ASA 125. Faster films tend to be more grainy than slower films, but they're an advantage when you're shooting in low-light situations.

You will learn much more about ASA and its effect on exposure and development in the main body of this book, but the essential concept is as simple as that. See Appendix N.

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