ISO Plays a Powerful Role in Portrait Photography

With portrait photography, ISO is an important setting that is commonly adjusted to make sure you end up with a great photo. Camera ISO controls how sensitive our camera image sensor is to light. A lower ISO means that the image sensor has a low sensitivity to light. If we set a lower ISO and the image sensor is less sensitive to light, then it will allow less light to be captured, but with high level of detail. If we increase the ISO then the image sensor becomes more sensitive to light. As the image sensor has an increased sensitivity to light, it allows more light in, but at the cost of having less granular detail. We can almost think of it like this. If the image sensor is more sensitive to light, it will allow more light in, but it is agitated by the light because it’s really sensitive to the light. The image sensor allows more light in as its sensitivity is increased, however, the image quality is reduced. The image quality is reduced because as the ISO goes up, there will be more noise in the photo. The lower ISO means less noise and more detail. When shooting portrait photography, it is important to understand how ISO affects your final product.

This may sound a lot harsher than it really is. Professional cameras today have really good image sensors and are capable of create awesome results in portrait photography. The amount of degradation between an ISO of 100 and an ISO of 1600 is very little and often unnoticeable. So why do we use ISO and what does it do for us in portrait photography? We control ISO so that we can control how much light is captured by the image sensor. The lower the ISO, the darker the image. The higher the ISO, the brighter the image.

In my personal opinion, ISO is always the last adjustment that we make. This means that in my experiences with portrait photography, I’ve always adjusted my aperture or shutter speed first. Once I have determined the correct and appropriate shutter speed for my photo, I then determine what aperture I need to use. After my shutter speed and aperture have been decided upon for my portrait photography session, then I make a decision on where the ISO needs to be. This is my own personal preference and others may have a different opinion on the order for which they choose to make adjustments.

ISO Objectives with Portrait Photography

When determining what ISO to use in portrait photography, we have two objectives to consider when making this decision. We need to first determine how much light do we need in the photo. Because in my experiences with portrait photography I would have already adjusted my shutter speed and aperture. My only focus here will be how bright the image needs to be. If after making my shutter speed and aperture adjustments my image is still slightly darker than I would like then I would increase my ISO to make the image brighter. If my shutter speed and aperture have left the image bright, then I may decrease my ISO. Many people will often strive to use the lowest ISO setting possible. This setting is often right around 100. My personal preference is to use an ISO somewhere between 400 and 1600. If I feel like I might need to go beyond 1600, I’ll make certain that further adjustments to the aperture and shutter speed aren’t possible first.

If there is ever a situation where we absolutely have to increase ISO to a number that is very high such as 3200 or 5000, then our image quality will suffer from noise. However, in some scenarios if blasting the image with noise means that we still got the perfect photograph in our portrait photography session instead of missing it entirely, then who cares right? I would rather know that I captured the moment than to stress on the fact that I missed it entirely. This is what sets regular portrait photography apart from exceptional portrait photography. When our images do experience noise due to high ISO, this isn’t the end of the world. Adobe Lightroom and Photoshop both offer amazing noise reduction tools that can reduce the amount of noise shown in a photograph dramatically. With a little bit of practice and experimentation we can get a good idea of how much is too much and when to back off.

More Portrait Photography Tips

Once we have made the correct adjustments to our ISO, there a couple of other adjustments that we can make to our camera to help make sure our image comes out the best. Learn more about aperture control in portrait photography with this article here. If you would like to learn more about shutter speed then check out this article we wrote explaining how shutter speed works. We also have a portrait photography article that explains how to make adjustments to all three using the same method I use when I’m out in the field taking photographs.

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