What is film speed?
Film speed is a measure of a photographic film’s sensitivity to light. It is expressed as an ISO number and determines the film’s ability to capture an image in low light conditions. The higher the ISO number, the more sensitive the film is to light, allowing for faster shutter speeds and lower light conditions. Lower ISO numbers indicate less sensitivity and are typically used in bright light conditions. Film speed is an important factor to consider when selecting a film and determining the exposure settings for your camera.
What are the different film speed standards?
There are several film speed standards that are commonly used in photography:
- ISO (International Organization for Standardization): The ISO standard is widely used and is the most common system for expressing film speed.
- ASA (American Standards Association): The ASA standard was used in the United States until the ISO standard became widely adopted.
- DIN (Deutsches Institut für Normung): The DIN standard is used in Europe, particularly in Germany.
- GOST (aka ГОСТ): This was the Soviet Union’s standard in use from 1951 until the Union’s collapse in the early 1990s.
- BS (British Standard): The BS standard was used in the United Kingdom and is similar to the ISO standard.
Today, the ISO standard is the most widely used and recognized film speed standard in the world. Film speed is expressed as an ISO number (e.g. ISO 100, ISO 400, etc.), and the higher the number, the more sensitive the film is to light.
Film speed vs. Digital Sensor ISO
Film speed and digital sensor ISO are two measures of a camera’s sensitivity to light, but there are some key differences between the two.
- Film speed: Film speed refers to the sensitivity of a photographic film to light and is rated using an ISO number (e.g. ISO 100, ISO 400, etc.). A lower ISO number indicates a lower sensitivity to light and is used in bright light conditions, while a higher ISO number indicates a higher sensitivity to light and is used in low light conditions.
- Digital sensor ISO: Digital sensor ISO refers to the sensitivity of a digital camera’s sensor to light and is also rated using an ISO number. The ISO setting on a digital camera allows the camera to adjust its sensitivity to light, just as film speed does. A digital sensor ISO setting of 100 is considered low, while a setting of 800 or higher is considered high.
In general, the ISO values for film and digital cameras are similar, but the way the ISO is adjusted and the resulting image quality can be different. Digital sensors can often handle higher ISO values than film, and the increase in noise (graininess) is often more gradual with a digital sensor. On the other hand, film has a unique look and character that is often preferred by some photographers, and the grain structure of film can add a desired texture to images.
Slow vs. Fast film
Slow film and fast film refer to the film speed of a photographic film, and the differences between the two types of film are primarily related to the film’s sensitivity to light.
Slow film (typically ISO 100 or lower) is less sensitive to light, and is used in bright light conditions. Slow film allows for finer grain, better color saturation, and less noise (graininess) in images.
Fast film (typically ISO 400 or higher) is more sensitive to light, and is used in low light conditions. Fast film allows for faster shutter speeds and lower light conditions, but at the cost of increased noise and a grainier image.
In summary, slow film is best used in bright light conditions and produces high quality images with fine detail and accurate color representation, while fast film is best used in low light conditions and sacrifices some image quality for the ability to capture images in less light.
Low ISO film (typically ISO 100 or lower) is used for bright light conditions and allows for finer grain, better color saturation, and less noise (graininess) in images. Some common scenarios where low ISO film is used include:
- Outdoor photography in bright light: Low ISO film is ideal for outdoor photography in bright sunlight, as it allows for accurate color representation and fine detail in the image.
- Studio photography: Low ISO film is often used in studio photography where the lighting is controlled and bright.
- Landscape photography: Low ISO film is well-suited for landscape photography, as it can capture the fine detail and rich colors of landscapes and nature.
- Portrait photography: Low ISO film can be used for portrait photography to achieve a natural skin tone and accurate color representation in clothing and backgrounds.
In general, low ISO film is used in situations where there is enough light to produce a well-exposed image without a high ISO setting. This allows for better image quality, with less noise and more accurate color representation.
Fast film refers to a type of photographic film with a high sensitivity to light. It is typically rated with an ISO number of 400 or higher and is used in low light conditions, where there is not enough light to produce a well-exposed image with a lower ISO setting.
Fast film allows for faster shutter speeds and lower light conditions, which is useful in a variety of situations, such as:
- Indoor photography: Fast film is often used in indoor photography where the lighting is low and flash is not allowed.
- Sports and action photography: Fast film is well-suited for sports and action photography, as it allows for fast shutter speeds and low light conditions to capture fast-moving subjects.
- Concert photography: Fast film is often used in concert photography to capture images in low light conditions.
- Street photography: Fast film can be used for street photography to capture images in low light conditions without using a flash.
However, fast film also has some limitations. One of the major disadvantages is that it produces a grainier image than slow film, and the image may be less sharp and have reduced color saturation.
Film speed vs. Exposure Index (EI)
Film speed and exposure index (EI) are similar concepts in photography, but they are not exactly the same.
Film speed refers to the sensitivity of the film to light, and is expressed as an ISO number (e.g. ISO 100, ISO 400, etc.). It is determined by the emulsion and manufacturing process of the film and is a characteristic of the film itself.
Exposure index (EI) is a chosen ISO setting used by the photographer to rate the film in the camera. It refers to the ISO setting that the photographer chooses to use when exposing the film, regardless of the film’s actual ISO speed. The EI can be higher or lower than the film’s true ISO speed, depending on the photographer’s preference and the lighting conditions.
In summary, film speed refers to the inherent sensitivity of the film to light, while exposure index refers to the ISO setting used by the photographer when exposing the film.
Film speed and processing
Push and pull processing are two techniques used to alter the processing of photographic film to change its sensitivity to light.
- Push processing: Push processing is a technique where the film is intentionally over-developed, increasing its effective ISO rating. This allows the film to be used in low light conditions, or to freeze fast-moving action, with a faster shutter speed. However, push processing also increases the amount of grain (noise) in the image, and reduces the overall image quality.
- Pull processing: Pull processing is a technique where the film is intentionally under-developed, decreasing its effective ISO rating. This is used in bright light conditions to reduce the amount of grain (noise) in the image, and to achieve a finer grain, better color saturation, and less noise.
Push and pull processing are typically used by experienced photographers who want to fine-tune the exposure of their film and achieve a specific look in their images. These techniques can also be used to overcome limitations of a particular type of film or to adapt to changing lighting conditions.
Film speed and reciprocity
Reciprocity refers to the relationship between the amount of light and the exposure time, with some films having deviations from the standard linear relationship at long exposure times. This deviation is known as reciprocity failure, and it can lead to over- or under-exposure, a change in color balance, and other image quality issues. Photographers must compensate for this by adjusting their exposure time or aperture, or using special film-specific reciprocity correction formulas.