ISO (International Organization for Standardization) is a standardization system that defines the sensitivity of film and digital camera sensors to light. In the film era, ISO was referred to as ASA (American Standards Association) and DIN (Deutsches Institut für Normung).
The sensitivity was denoted by film speed, where lower numbers indicated lower sensitivity (less sensitive to light) and higher numbers indicated higher sensitivity (more sensitive to light). With the transition to digital cameras, the same ISO terminology and scale were retained to provide consistency and familiarity to photographers.
The American Standards Association (ASA) was a former organization that played a significant role in the standardization of film speed for photographic film in the United States. Established in 1931, ASA developed the ASA film speed rating system, which indicated the film’s sensitivity to light.
The ASA scale typically ranged from ASA 25 to ASA 1600, with higher values indicating higher sensitivity to light. ASA collaborated with other standardization bodies to ensure consistency in film speed ratings internationally. In 1966, the ASA merged with the United States of America Standards Institute (USASI) to form the American National Standards Institute (ANSI), which continues to be involved in setting various standards, including those related to photography and imaging.
The change from ASA to ISO in the context of film speed ratings occurred in the early 1980s. In 1974, the ASA and the DIN collaborated to develop a joint standard for film speed ratings, using ASA and DIN film speed values together. This resulted in the ISO system we know today, which was first published in 1980 as ISO 5800:1980.
The adoption of the ISO standard allowed for global harmonization of film speed ratings, simplifying the process for photographers and ensuring consistent and comparable results across different countries and regions. Since then, the ISO film speed rating system has been widely used in both film and digital photography to indicate the sensitivity of camera sensors or film to light. ISO settings determine how sensitive the camera sensor is to light.
While ISO influences how much light the sensor can capture, it does not directly control the amount of light entering the camera like the aperture and shutter speed do. Instead, ISO affects the amplification of the captured light signal, resulting in brighter or darker images. The primary reason ISO is not considered part of the exposure is that changing the ISO does not impact the amount of light reaching the sensor; it alters the sensor’s sensitivity to that light. Therefore, understanding ISO and its implications is vital for achieving well-exposed images, especially in challenging lighting conditions.
Higher ISO values make the sensor more sensitive, allowing you to capture images in low-light conditions, but they may introduce more digital noise (graininess) into the image.
Lower ISO values make the sensor less sensitive, resulting in cleaner images with less noise but requiring more light to achieve a well-exposed shot. ISO values typically range from 100 (or lower) to 3200 and beyond on modern cameras. The standard ISO values are usually: 100, 200, 400, 800, 1600, 3200, and so on, with each value doubling the sensitivity of the previous one.
Low ISO (e.g., ISO 100-400)
- Use low ISO in bright lighting conditions with plenty of available light.
- Ideal for capturing landscapes and scenes in daylight.
- Provides the best image quality with minimal noise.
Medium ISO (e.g., ISO 800-1600)
- Use medium ISO in moderate lighting conditions or when you need to balance exposure and image quality.
- Suitable for indoor photography or overcast outdoor conditions.
High ISO (e.g., ISO 3200 and above)
- Use high ISO in low-light situations or when you need to freeze fast-moving subjects without using a flash.
- Useful for night photography, concerts, and indoor sports events. Example: Capturing fast-action shots of a basketball game in a poorly lit gym using ISO 3200.
ISO is one of the three exposure settings, along with aperture and shutter speed. When adjusting ISO, consider how it affects exposure and image quality, and balance it with the other settings to achieve your desired outcome. High ISO + Wide Aperture (low f-stop): Suitable for low-light situations but may result in shallow depth of field. Low ISO + Narrow Aperture (high f-stop): Suitable for well-lit scenes and landscapes, providing a larger depth of field.
Different photography situations along with suggested ISO, shutter speed, and aperture settings
- Landscape Photography (Daylight):
- ISO: 100
- Shutter Speed: 1/125 to 1/250 sec (to freeze any slight movement)
- Aperture: f/8 to f/16 (for a larger depth of field)
- Portrait Photography (Outdoors):
- ISO: 100-400 (depending on lighting conditions)
- Shutter Speed: 1/125 to 1/250 sec (to capture subjects without motion blur)
- Aperture: f/2.8 to f/5.6 (for a pleasing background blur and subject separation)
- Night Photography (Cityscape/Urban):
- ISO: 800 to 3200 (to capture the low-light environment)
- Shutter Speed: 1/30 to 15 sec (for city lights and light trails)
- Aperture: f/4 to f/8 (to balance sharpness and light gathering)
- Action/Sports Photography (Outdoors):
- ISO: 400 to 800 (adjust higher for lower light conditions)
- Shutter Speed: 1/500 to 1/2000 sec (to freeze fast-moving subjects)
- Aperture: f/4 to f/5.6 (for a wider aperture and faster shutter speed)
- Indoor Photography (Low Light):
- ISO: 800 to 3200 (depending on available light)
- Shutter Speed: 1/60 to 1/125 sec (to avoid camera shake)
- Aperture: f/2.8 to f/4 (for better light gathering)
- Macro Photography:
- ISO: 100 to 400 (adjust based on lighting conditions)
- Shutter Speed: 1/60 to 1/250 sec (to prevent blur from camera shake)
- Aperture: f/11 to f/16 (for a deeper depth of field)
- Wildlife Photography (Telephoto Lens):
- ISO: 400 to 800 (adjust based on lighting and subject movement)
- Shutter Speed: 1/500 to 1/1000 sec (to freeze fast-moving animals)
- Aperture: f/5.6 to f/8 (to maintain sharpness)
- Silhouette Photography (Sunset/Sunrise):
- ISO: 100 to 200
- Shutter Speed: 1/500 to 1/1000 sec (to capture the bright sky)
- Aperture: f/16 to f/22 (for a well-defined silhouette)
Remember that these settings are just starting points and can be adjusted according to the specific conditions, creative intent, and the effect you want to achieve in your photographs. Photography is an art, and experimentation is encouraged to find the best settings for your unique situations. Note: The actual settings may vary depending on the available light, camera model, lens, and other factors.
Always consider the specific conditions and make adjustments as necessary. [Note: The above settings are based on typical scenarios and should be adjusted according to specific shooting conditions and creative vision. Remember that these settings are just starting points and can be adjusted according to the specific conditions, creative intent, and the effect you want to achieve in your photographs.
Photography is an art, and experimentation is encouraged to find the best settings for your unique situations. Note: The actual settings may vary depending on the available light, camera model, lens, and other factors. Always consider the specific conditions and make adjustments as necessary. [Note: The above settings are based on typical scenarios and should be adjusted according to specific shooting conditions and creative vision.]
- “Basic Camera Settings” (Last updated: May 23, 2022) https://photographycourse.net/the-basic-camera-settings/
- Understanding ISO Sensitivity in Digital Photography” by Photography Life: https://photographylife.com/what-is-iso-in-photography
- “The Complete Guide to Understanding and Using ISO in Photography” by PetaPixel: https://petapixel.com/2017/07/31/complete-guide-understanding-using-iso-photography/
- “ISO Settings in Digital Photography” by Digital Photography School: https://digital-photography-school.com/iso-settings-in-digital-photography/
- Wikipedia (accessed July 23, 2023) https://en.wikipedia.org/wiki/International_Organization_for_Standardization