maxing out ISO levels: a closer look at camera settings adjustments

maxing out ISO levels: a closer look at camera settings adjustments

Underwater photography presents unique challenges, with low light conditions being one of the most prevalent. To capture vibrant images in these circumstances, photographers often need to make compromises, such as lowering shutter speed and aperture. One such compromise is the careful adjustment of ISO, the standard for light sensitivity in photography, originally defined by the International Standards Organization.

Increasing ISO allows better exposure in low-light underwater environments, but it comes at a cost. Raising the ISO amplifies the sensor's signal, making the image brighter. However, this amplification also increases electronic noise, which appears as grain or speckles in the image. Modern cameras handle high ISO better than older models, but some noise is inevitable at higher ISO values.

Increased ISO generally reduces a camera's dynamic range, the difference between the darkest shadows and brightest highlights that the sensor can capture. As a result, images shot at higher ISO may lose detail in shadow and highlight areas, a problematic scenario underwater where contrast is already compromised by water scattering and absorption.

Due to reduced dynamic range and increased noise at higher ISO, post-processing to recover details in shadows and highlights becomes more difficult. Noise in shadow areas may become pronounced when trying to brighten them, and highlights may clip more easily, limiting adjustment latitude.

Underwater images often suffer from low contrast, color casts, and backscatter. Higher ISO can exacerbate noise and reduce image clarity, making careful use of lighting (strobes) and proper camera settings essential. Balancing ISO with aperture and shutter speed is critical to optimize exposure without overly degrading image quality.

Each camera manufacturer treats ISO slightly differently, leading to a destandardization of the setting. Some camera companies, like Sony and Panasonic, equip their cameras with sensors optimized for two different base ISOs (dual gain ISO). With dual gain ISO cameras, the noise levels will drop at a certain ISO, but this can lead to a situation where noise at a higher ISO is higher than at a lower ISO.

In a recent Canadian dive trip, the author used an ISO of 2500 on a Nikon Z6 to capture colours in both the subject and background. When shooting at high ISOs, it is essential to expose the image properly to collect as much detail as possible. Changes in ISO do not translate to linear changes in the gain, and the precise voltages applied will vary.

Noise can occur at multiple points in the pathway from photon to digital signal, including the analog amplifier and the ADC. A larger sensor can collect more light and produce less noise at higher ISOs, but this is more related to pixel size than sensor size.

In extremely bright lighting conditions, it is recommended to leave the ISO at the base/native ISO for the cleanest, most detailed image. The base or native ISO of a camera is the lowest ISO value that provides the cleanest photo with the least amount of noise and highest level of dynamic range.

In summary, increasing ISO allows better exposure in low-light underwater environments but at the cost of increased noise, reduced dynamic range, and challenges in recovering shadow/highlight details during post-processing. Photographers must carefully balance ISO with other settings and lighting to achieve the best image quality underwater. Modern cameras with advanced sensors mitigate some of these effects but cannot fully eliminate them.

1. To tackle the low light conditions in underwater photography, photographers often adjust ISO, a setting defined by the International Standards Organization, for better exposure.
2. Increasing ISO, though improving exposure, inevitably amplifies the sensor's signal, leading to electronic noise that appears as grain or speckles in the image.
3. Higher ISO generally reduces a camera's dynamic range, compromising the detail in both shadow and highlight areas, a challenge underwater where contrast is already compromised.
4. Post-processing recovery of details in shadows and highlights becomes more difficult with increased noise, especially in underwater images that often have low contrast, color casts, and backscatter.
5. Careful use of lighting (strobes) and proper camera settings, such as balancing ISO with aperture and shutter speed, is essential to optimize exposure without overly degrading image quality.
6. Some camera manufacturers, like Sony and Panasonic, have dual gain ISO, which affects the noise levels, with noise dropping at a certain ISO but potentially becoming higher at higher ISOs.
7. On a recent Canadian dive trip, the ISO of 2500 was used on a Nikon Z6 to capture vibrant colors, emphasizing the importance of exposing images properly to collect as much detail as possible at high ISOs.
8. Noise can occur at multiple points in the pathway from photon to digital signal, and a larger sensor can help reduce noise at higher ISOs, though this is more related to pixel size than sensor size.
9. In all but the brightest lighting conditions, it is recommended to use an ISO lower than the base/native ISO for the cleanest, most detailed image, as the base ISO provides the least amount of noise and highest level of dynamic range.

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