It is possible to develop color negatives in black and white, although it may require some fiddling and it will certainly require some special contrast filters to compensate for the differences between the negatives. There are numerous advantages to developing color negatives as black and white prints, and the images you produce can be quite stunning if you are willing to take the time to experiment with filters and exposure levels.
Color film has several layers, each of which is sensitized to a different color. When the film is developed, the exposure is fixed, creating a negative. When the negative is exposed to color-sensitive paper and developed in color developing chemicals, it will result in a color print. If you develop color negatives using a black and white technique, the color information will be retained, but the print will be in rich shades of black, gray, and white. This monochrome print can have an almost unearthly feel if it is developed well, and it is fun to experiment with color negatives in a black and white darkroom.
To develop color negatives as black and white photos, you will need access to a darkroom along with an enlarger and trays of photographing chemicals. You will also need black and white enlarging paper, and a set of filters. Filters are thin slips of colored gel that can be interposed between the negative and the developing paper, changing the look of the exposure. Many stores sell packs of contrast filters, often labeled with Wratten Numbers, a standardized system used to describe them.
You can try making a straight black and white print from a color negative, but the contrast usually looks very strange. As a result, you need to explore the wide world of filters. Start with a light yellow one, and play around from there; many people recommend starting out with a four filter. You will use a lot of photo paper in this process; what you're looking for is the perfect filter, exposure, and focus. Take your time and don't let yourself rush through your work.
To develop color negatives in black and white, load the negative into the enlarger and focus it as you would normally. Try making a test strip without a filter first, so that you have a basis for comparison. To make a test strip, cut a strip of photo paper and place it under the enlarger. Use a piece of heavy cardboard to cover most of the test strip, and turn the enlarger on. Every two seconds, move the cardboard further back, until you have a range of exposures. Develop the test strip, take it outside, and look at the exposure. Your first test strip will probably not look very good, but after several strips using filters, you will find the perfect filter and exposure to use.
Once you develop a whole piece of enlarging printer, using the parameters on your test strip, you may notice areas of the photograph that need touchups such as dodging and burning. Over-exposed areas should be “dodged,” meaning that you obstruct the light source with a dodging tool while the paper is exposed to reduce the amount of exposure in the relevant area. Burning involves correcting underexposure with a targeted longer exposure, typically by using heavy cardboard or metal with a small hole in it which lets light through to the area of interest.
The process of turning color negatives into black and white prints can be trying and frustrating, but the results are often very interesting. An ideal print combines the stark, clean look of black and white prints with the visually lush contents of color prints, and you can even tone the resulting print with sepia or another color for added impact.