Exposure Latitude

Exposure latitude is how much a certain film can withstand the overexposure and/or underexposure condition and still be able to produce acceptable image quality with normal processing.


A few parameters for film's exposure latitude

  • Film's type

  • Inherent design

  • Speed

  • Subject brightness ratio

  • The method or specific chemistry used in processing could all be important determinants.

Here are some guidelines with respect to film latitude:

  1. Slow films generally exhibit narrower exposure latitude than do medium or high speed emulsions.

  2. Black-and-white and color negative material offer significantly more latitude than do transparency films.

  3. Negative materials show much more overexposure latitude than on the underexposure side. For some negative films, this can amount to two or three times as much overexposure latitude.

  4. Transparency films are much more tolerant of underexposure than of overexposure. They exhibit at least twice as much latitude on the underexposure side. Even so, transparency films have the least exposure latitude of any film type.

  5. Exposure latitude is greatest when film is used to photograph subjects under low-contrast lighting. It follows that as subject contrast increases, exposure latitude decreases.

  6. Exposure latitude is controversial because:
    a. There is no objectively correct exposure.
    b. What appears to be a well-exposed frame to one observer is over- or underexposed to another.
    c. Published exposure latitude figures are judgments and represent consensus at best.

  7. Exposure latitude is up to 50 percent greater when shooting under even, diffused light (as on an overcast day) than under bright, direct sunlight or non-diffused electronic flash.

  8. A majority of experienced photographers indicate the best starting point for exposure is to rate the film at its manufacturer's recommended ISO. Numerous published tests confirm this judgment. The ratings were arrived at by taking an average of ISOs used by the panel of expert photographers working with the author on the preparation of this volume. While many felt the rated ISO was optimum, especially in low-contrast light, numerous films were rated at ISOs other than their designated speed.

  9. It is of interest to note that almost all panel members used personal EIs (Exposure Indices) different from manufacturer recommendations when using slide film and were more likely to accept nominal speed ratings for print film. This is probably due to the wide exposure latitude inherent in print film as compared to slide material.

  10. In practice, applying corrections to established ISO numbers sets a personal exposure index most suitable for your own equipment, applications, and taste. Even though stated ISOs are used by many photographers, they should not represent an absolute value.

More about film photography

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