What is Depth of Field in Film Photography?
Depth of field is one of many basic film photography tips to heighten the look of a photograph. In short, it is the distance between the foreground and background of the subject that appears to be in focus. There are two types of depth of field – shallow and great. Shallow depth of field involves one point of focus with the foreground and/or background blurred. Conversely, great (maximum) depth of field puts nearly everything in focus. Change in depth of field is not an immediate transition between sharp to unsharp. Instead, there is a gradual transition of sharpness to fuzziness to totally out of focus areas.
How to Control Depth of Field
with Basic Photography Tips
Depth of field is controlled, mostly, by the aperture settings of a film camera lens. It can also change depending on the focal distance of the subject to your camera. With aperture settings, the larger the aperture opening (smaller f-stop numbers) and closer the focal distance, the shallower the depth of field will result. On the other hand, small aperture openings (larger f-stop numbers) and farther focal distances will equate to a greater depth of field.
Great Depth of Field and Diffraction
While any guide to photography will point out that the smallest aperture should be used any time the photographer wishes to have the greatest depth of field, this will pose two problems. The immediate problem is that you will likely need to use a tripod as the shutter speed will be long. The second issue is what is known as diffraction. Diffraction is an optical effect that will cause some softening effects that will offset any gain in sharpness due to the smaller aperture. This effect is usually negligible, particularly for standard 35mm single lens reflex (SLR) cameras that most will use for beginner photography. However, it should be noted to help you limit and avoid any softening due to diffraction.
Diffraction happens as the small aperture brings in light rays. These light rays normally pass through a film camera lens parallel to each other. But when smaller apertures are used the light rays will begin to veer and interfere with one another. This unbalance of light rays will cause a softening look to your photographs. Again, diffraction occurs to some extent at all levels of film photography but is only noticeable as the size of the aperture significantly decreases.
Photography Tips for Testing Depth of Field with Film Cameras
Much like the rest of film photography, you will not know for sure how your image looks until it is developed and processed. However, many newer 35mm film cameras and lenses have a feature called depth of field preview. After setting your aperture you can press a button on your camera body to preview the depth of field through your viewfinder. This is a great built-in photography guide for those who are learning, and you may want to consider purchasing a camera and lens that support this previewing. Please note, however, that depth of field preview has some flaws. When you set your aperture to a smaller opening, less light is allowed through the camera lens and the image will appear dark through the viewfinder. In some instances, your viewfinder will be too dark to even view the preview. Please note your image will not turn out this dark if you correctly set the shutter speed for proper exposure.
If you do not have a depth of field preview setting for your camera it would be best to take multiple photographs of the same scene using different apertures so that you can see for yourself which aperture will yield which amount of sharpness.