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There are higher chances of overexposure when shooting real estate exterior photos in broad daylight or underexposure when shooting interior photos in poor-lit situations. With the following exposure compensation vs. ISO guide, you will know which settings to adjust to get the right exposure.
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Both the exposure compensation and ISO are camera settings that help to increase the exposure and brighten a subject or reduce the exposure and darken a subject depending on the contrast and lighting conditions.
Exposure Compensation (EC) is a camera setting that helps to override the shutter speed, ISO, or aperture settings to allow more light to reach the camera sensor and brighten a photo or reduce the amount of light reaching the camera sensor to darken the photo.
Keeping in mind that the camera light meter is standardized on 18% gray, which is the middle gray, and works by determining the light reflected by the subject, it can get the wrong exposure when shooting in extremely backlit conditions or extremely high contrast situations.
The EC solves this problem by compensating for the exposure when the camera light meter gets the exposure wrong. Usually, cameras come with an EC button that allows you to manually increase or reduce the exposure when shooting.
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Generally, the camera ISO setting controls the amplification of the resulting voltage or digital signal. Keeping in mind that the camera sensor is an electronic device, it has electronic signal interference in its operation.
Since the sensor amplifies the light signal just like how the sound amplifier’s gain control amplifies sound, the amplification of the light signal goes hand in hand with the amplification of the interferences, causing a digital noise when using higher ISO settings.
Keeping in mind that ISO controls the amplification of the light signal reaching the camera sensor while the EC helps to rectify the exposure when the camera light meter evaluates the lighting condition of a scene wrongly and gets the wrong exposure, the two settings have the following exposure control similarities and differences.
Although the EC and ISO operate differently, the following similarities make both of them capable of increasing or decreasing the brightness of an image.
Even if both the EC and ISO can brighten or darken an image, the two settings have the following operation differences and effects on the resulting image.
Most modern cameras allow you to control the members of the exposure triangle automatically, semi-automatically, or manually. Keeping in mind that the members of the exposure triangle are shutter speed, aperture, and ISO, it means ISO can be automatically or semi-automatically controlled.
On the other hand, since the EC is not a member of the exposure triangle, it can control the members of the exposure triangle. That means the EC can automatically adjust the camera ISO to increase or reduce the exposure, yet ISO can’t control it.
For instance, EC can adjust the ISO and shutter speed when in A/Av mode, aperture, and ISO when in S/Tv mode, or any of the three when in P mode. However, it can’t control anything when in manual mode.
Bokeh refers to the beautiful background blurring when using selective focus techniques. The effect helps to emphasize the main subject, especially when shooting portraits. Generally, you will get this beautiful background blur when using the widest aperture.
However, if you are shooting in bright lighting, the wide aperture can result in overexposure. Usually, reducing the ISO to the base ISO of 100 will help reduce the exposure without affecting the bokeh quality, regardless of the shooting mode.
On the other hand, using the negative EC to reduce the exposure can significantly affect your bokeh quality if you use the camera in automatic or Shutter Priority mode. Typically, it is because the EC will try to reduce the exposure by narrowing the wide open aperture.
Usually, different members of the exposure triangle have their maximum limits, such as the maximum wide aperture, fastest shutter speed, and the highest ISO setting. However, since the EC doesn’t fall in this category, it has a flexible limit.
For instance, if you are using the ISO to reduce the exposure, you will have a limit of the base ISO of 100. Increasing the exposure means you will have a maximum ISO limit depending on the camera model. For instance, the maximum ISO for the Sony A7s is ISO 102400.
On the other hand, EC can increase or reduce the settings of any member, giving it flexibility. For instance, when increasing the exposure, EC can set the maximum ISO, widest aperture, and slowest shutter speed, and vice versa when reducing the exposure.
The major distinguishing factor between exposure compensation and ISO is the image noise. Since the ISO works by amplifying the light signal, a high ISO setting amplifies the electronic interferences, causing digital noise visible on the images as artifacts or graininess. As a result, the image loses details and seems low-quality.
On the other hand, EC is flexible and doesn't necessarily have to adjust the ISO to improve exposure. That means EC can adjust other members of the exposure triangle and increase the image brightness without causing any image noise.
Since the EC doesn't cause image noise and has a flexible limit that can reduce the exposure lower than that of the ISO 100, it might be the best option to use in the following situations.
Keeping in mind that ISO is a member of the exposure triangle, it might be the best setting to brighten or darken photos in the following conditions.
ISO is the best setting to use to increase or reduce the exposure as it can brighten an image without affecting the shutter speed and the aperture settings. Usually, this makes it possible to get the right bokeh quality with a wide open aperture or capture sharp and crisp photos of a moving subject.
However, if you are shooting in trying lighting where the camera light meter can't get the right exposure, the EC is the easiest way to improve the exposure.
If you are shooting in trying lighting conditions, you can adjust the ISO or EC to get the right exposure. With the above exposure compensation vs ISO, you will know when the camera light meter is wrong and use EC and when the scene is poorly-lit and use ISO.
