ISO makes up one of the three parts of the exposure triangle and is vital to understand when choosing the optimal settings for a photographic exposure. In this article, What You Need To Know About ISO, we look at ISO and using it effectively to achieve the best image quality.
1. What Is ISO?
ISO is one of the elements of the exposure triangle that determines the brightness of an image. However, unlike aperture and shutter speed which have a physical impact on the exposure of a photograph, the ISO works by raising or lowering a camera’s sensitivity to light.
By increasing the ISO setting, an exposure will get brighter. Conversely, lowering a cameras ISO will decrease the brightness of an image. However, increasing this sensitivity will also increase the grain or “digital noise” of an image. Raising the ISO of exposure this way will result impact the overall image quality of a photograph.
ISO stands for International Standardisation of Organisation, the group that first established the standards for light sensitivity to analogue film. Before 1974 there were two film standards named DIN and ASA. These were then combined to create ISO. And although this term formally referred to camera film, camera manufacturers later adopted it to refer to light sensitivity in digital photography.
2. How Is ISO Measured?
ISO levels vary between camera manufacturers and models. However, the standard of these levels remains consistent. The most common ISO levels are:
By raising or lowering the ISO setting, a camera is doubling or halving its sensitivity to light. In this instance, an ISO setting of 800 means a camera is twice as sensitive to light as it would be at 400.
3. The Relationship Between ISO And Image Quality
The ISO used for exposure will have a direct relationship to its image quality. This result is because raising the ISO setting will increase the grain or digital noise in the image. This image noise is unattractive in photography as it drastically reduces the image’s sharpness. Furthermore, the dynamic range will also decrease the higher an ISO becomes.
4. What Is Base ISO?
Base ISO is the lowest possible ISO setting a camera is capable of using. This setting is crucial because it inevitably results in the highest possible quality photographs a camera can produce. Most modern cameras are capable of ISO settings of 100.
Sticking to this base ISO should always be the first consideration when choosing the optimal exposure settings for an image. However, this is not always possible, especially in low light conditions.
5. How To Determine The Best ISO Settings
It is important to note that there are no optimal ISO settings for different scenes. The setting chosen will inevitably depend on the amount of light available for a camera sensor to record and the range of motion you wish to capture in an image.
As a rule, it is always preferable to maintain a camera’s base ISO setting where possible. However, as a scene becomes darker, a higher ISO setting will need to be used. For example, a well-lit daytime scene can be recorded at a low ISO setting while maintaining control over the aperture and shutter speed. On the other hand, shooting something like a night sky will require an ISO of 3200 to 6400.
6. Methods Of Reducing ISO and Digital Noise
When choosing the optimal ISO settings for a photograph, it is best to set the aperture to the requirement first. From here, select the camera’s base ISO option. Next, choose a shutter speed that balances the exposure to an EV rating of 0. If the subject is blurry in this setting, increase the ISO to increase the shutter speed. If the ISO becomes so high that the image quality drops, you can widen the aperture, even if it means losing the desired depth of field in the image.
The most important takeaway from this article is to understand the relationship between ISO and image quality. It should always be your first aim to capture your photographs to the best quality possible. However, as we have discussed, this is not always possible.
When shooting in manual mode, be sure to follow the steps provided above to ensure you capture images with the highest level of detail, sharpness and dynamic range. The sacrifices necessary and the best ISO settings for each scene will become second nature the more you practice. So pick up your camera and spend some time trying to achieve the lowest ISO settings possible for different environments and subjects. Happy shooting!
What You Need To Know About ISO, What You Need To Know About ISO, What You Need To Know About ISO.