Raw Photography: Mastering Iso Sensitivity

When shooting in RAW, the ISO setting is important because it determines how the camera treats the footage to give you a preview. The ISO setting essentially says where the midtones are and affects how you expose the image and balance shadows and highlights. While the ISO setting does not affect the quality of the image, it does impact the preview and how the image is processed.

ISO settings can be changed in post-processing

The ISO setting on your camera is a measure of its sensitivity to light. The ISO setting can be changed in post-processing, but it is important to understand the implications of doing so.

When shooting in RAW, the ISO setting affects the amount of light that reaches the camera sensor. A higher ISO setting will result in a brighter image, while a lower ISO setting will result in a darker image. However, increasing the ISO can also introduce noise into the image, resulting in a grainy or "chunky" appearance. Therefore, it is generally recommended to keep the ISO setting as low as possible to achieve the desired exposure.

That being said, there may be times when you need to increase the ISO setting to achieve a specific shutter speed or freeze motion in your photo. For example, when photographing the Milky Way, you will need to use a fast shutter speed to capture the stars without motion blur. In this case, you may need to increase the ISO setting to achieve the desired shutter speed, even if it means introducing some noise into the image.

It is important to note that not all cameras handle ISO adjustments in the same way. Some cameras, like those from Nikon and Fuji, are considered "ISO-less" or "ISO invariant," meaning that you can adjust the ISO setting in post-processing without any significant loss in image quality. Other cameras, like those from Canon, are not ISO-less, and you may notice a difference in image quality when adjusting the ISO setting after the fact.

When shooting in RAW, it is generally recommended to use the lowest ISO setting that allows you to achieve the desired shutter speed and exposure. This will give you the cleanest image possible, with minimal noise. However, there may be times when you need to increase the ISO setting to capture the photo you want. In these cases, it is helpful to understand the capabilities and limitations of your specific camera model to determine how much you can adjust the ISO setting in post-processing without sacrificing image quality.

Overall, while it is possible to change the ISO setting in post-processing, it is important to understand the impact of doing so on your final image. By carefully considering the lighting conditions, subject matter, and capabilities of your camera, you can make informed decisions about ISO adjustments to achieve the best possible results.

ISO affects your metering

Firstly, ISO is one of the three pillars of photography, along with shutter speed and aperture. Therefore, it has a major effect on your images.

Secondly, ISO is like a mapping that tells your camera how bright the output photo should be, given a particular input exposure. This means that if you are locked at ISO 100 in Aperture-Priority mode, you might end up with a bad shutter speed. Even in manual mode, the meter will guide you incorrectly.

Thirdly, ISO can help you capture images in darker environments, or be more flexible about your aperture and shutter speed settings. For example, if you are photographing birds in flight, you will need a fast shutter speed to freeze their movement. If you set your ISO to 100, you will need a shutter speed of 1/250th of a second to capture a bright photo. At that setting, there would be a lot of unwanted motion blur in the picture. By raising your ISO, you can increase your shutter speed and capture a sharp, bright photo.

Finally, ISO is not part of the exposure. Shutter speed and aperture brighten your photo by physically capturing more light. ISO doesn't do that; instead, it essentially brightens the photo you already captured.

ISO-less cameras

In other words, an ISO-less camera will produce the same results in terms of image quality if you underexpose your photograph and then raise the exposure in post-processing as if you had exposed it correctly (in-camera) in the first place. This is because an ISO-less camera will allow you to increase exposure in post-processing without compromising quality.

Some examples of ISO-less cameras include:

• Sony A7RII
• Fuji XT1
• Nikon D810
• Nikon D750
• Nikon D7100
• Nikon D5500
• Pentax K5
• Olympus OMD-EM1
• Olympus OMD-EM5 II
• Sony A7S
• Sony Nex 7

It is important to note that no cameras are perfectly ISO invariant starting from base ISO. However, some are quite close, and many cameras become ISO invariant starting at a high enough ISO value.

ISO affects your RAW files

ISO, or International Organization for Standardization, is a setting on your camera that amplifies the data that your camera records. It is one of the three pillars of photography, the other two being aperture and shutter speed.

The ISO setting on your camera increases the analog signal before it is digitised, which is a source of noise. This means that the higher the ISO, the more noise will be visible in your image.

However, the impact of ISO on your RAW files depends on the camera you are using. Some cameras are "ISO-less" or "ISO invariant", where the ISO setting does not affect the RAW data. This includes modern Nikon and Fuji cameras. Canon cameras, on the other hand, are not ISO-less, and changing the ISO will affect the RAW data. Brands like Sony and Olympus fall somewhere in the middle, with a slight difference visible between ISO settings.

Even if you are using a camera that is ISO-less, the ISO setting will still impact your RAW files in a few ways:

• ISO affects your metering. If you are locked at ISO 100 in Aperture-Priority mode, you might end up with very slow shutter speeds.
• Using a low ISO will result in completely useless photos on your camera screen, even though you can brighten them in post-processing.
• ISO will affect your RAW files if you use a value so high that it blows out your highlights.

Tips for shooting in RAW

When shooting in RAW, it is generally recommended to use the lowest ISO possible while still getting a good exposure. This will help you avoid noise and maintain the best image quality.

Additionally, if you are shooting in low-light conditions and need to use a higher ISO, it is better to use a higher ISO and get a correctly exposed image rather than underexposing and trying to brighten it in post-processing. This is because underexposed images will have less data in the bright parts of the histogram, resulting in noisier images.

In conclusion, while the impact of ISO on your RAW files depends on your camera, it is still important to understand how ISO works and how it can affect your images. By using the appropriate ISO setting for your camera and lighting conditions, you can ensure that you capture the best quality images possible.

Long exposure noise reduction

This setting is available on most DSLRs and mirrorless cameras, and can be turned on or off as needed. However, it is important to note that using this setting will double the time required to take a photo, as the camera is unusable while the dark frame is being taken. Therefore, it is recommended to only use this setting when you can afford to double your exposure time, such as during a moonless night with unchanging conditions.

Frequently asked questions