I will start this part differently from the two previous parts, with a disclaimer and a little history. The disclaimer is in regards to the technical aspect of ISO, which I won’t delve into, since this is a basic introduction to ISO, and how to use it creatively as part of your photography, not an attempt at a technical explanation of how ISO works.
A little history. ISO is referring to the “film speed standard”, and is a combination of two older standards known as ASA and DIN. This was a standard for the measurement of the sensitivity of film used in the analog era, or the “film speed”, making it possible for photographers to know how sensitive a roll of film would be, depending on its ISO value, and thus how they should adjust the aperture and the shutter speed, in order to get the desired exposure. The higher the ISO value, the more sensitive the film would be – or the “faster” it would be (meaning that you could speed up the shutter speed), allowing the photographer to ensure they would get the right film for the right situations. For example, in cases where a photographer would have to do a shoot in low light circumstances, he could choose a film with a high ISO value.
However, the higher the ISO value of the film, the more grain would be introduced in the image. The chemical which would make the film more sensitive, would also affect the film with the graining of it, and this would cause the image to be more grainy, the higher the ISO value was.
Since the ISO was a constant value, depending on which ISO the film used, the two main aspects of the exposure were aperture and shutter speed. Granted, many would also consider flash as being a part of this, but we won’t be delving into flash photography here.
The use of ISO for determining the light sensitivity of the film has transferred into the digital realm of cameras as well. However, there are some differences in how it’s applied today in comparison to the film era. Whereas the ISO was determined by the film a photographer would use, today it is part of the controls of the camera, affecting the sensor directly. This means that we can always decide on the light sensitivity of the sensor, choosing to adjust the ISO as we go, according to the changing circumstances.
Another difference is the lack of a genuine standardization of the ISO values, which today are arbitrary, and decided by the camera manufacturers themselves. For example, many have pointed out that Fujifilm cameras have a lower exposure than other camera brands at the same ISO value. That said, all camera brands keep the ISO values relatively similar, since they acknowledge the problems they would cause for themselves if they decided to make their own system to define the light sensitivity, and for the most part there really isn’t that much difference in the sensitivity between the brands.
Where they do differ, is in how well their cameras handle high ISO. Some brands have better control over the high ISO performance and can offer better sensor technology to allow for more clean images in low-light situations. Among the full-frame camera options, Sony and Nikon are doing very well with the Sony A7 mIII and the Nikon Z6 respectively. For the APS-C cameras, Fujifilm does well with their cameras, compared to other APS-C cameras from other brands. However, because full-frame cameras have larger sensors, they will almost always do better than APS-C cameras, and other cameras with smaller sensors.
A third way the analog ISO standards for film differ from digital ISO values is in the grain vs noise of the digital sensors. Whereas grain often can have a pleasing effect, digital noise often can be harsh and very defined. This is caused by the noise being created by the individual pixels in the sensor, which is a square. This means that when a pixel appears as a noise signal, it will typically be shown as its form as a square. Some cameras manage to handle the noise better than others, in the way it’s displayed, making it seem more like film grain.
So there are two effects caused by the ISO. The one is the light sensitivity of the sensor. The higher the ISO, the more sensitive the sensor is to the light hitting it, and the brighter the image is. This means that if you are in a situation with little light, and you don’t want to slow down the shutter speed too much, and you can’t open the aperture more than it already is, you can then choose to raise the ISO. Just note that not all cameras have the same ISO range, typically starting with 100 as the base ISO (though for Fujifilm cameras it’s 160 or 200), being raised by doubling the value, which also makes the sensor double the sensitivity to the light hitting it, and thus making the image twice as bright for each stop of ISO you’re adding. Some cameras can only go to for example 12800, whereas others can go to 204,800 or even more. Just know that even though they can go this high, it might not be a smart idea to go this high, since the noise that will be introduced at these high values can degrade the image.
Shot with ISO 6400
The second effect of high ISO, as we already have mentioned, is the noise introduced in the image. The higher the ISO, the more noise will be introduced, and at some point enough noise can be introduced to make the image unusable, basically ruining the image and making it hard to see what is in the image. However, at lower high ISO values the noise can be used as a creative effect, giving some edge to the image. Maybe you’re taking photos of a ruin or other place which isn’t aesthetically pleasing, and you want to add some grain to give it a more edgy feeling. You can do this by raising the ISO high enough that enough noise will be introduced into the image, and then adjusting the aperture and shutter speed to lower the exposure as required. While we all want clean images in most cases, we might not always want them. The two images I have added as examples are images, where I purposefully added a high ISO value, in order to introduce a lot of noise to give that unclean aspect to them. In the case of the last image, you can see that there’s so much noise, that the image almost falls apart. In this particular case, I didn’t mind it, I liked it that way since it’s less about the actual image, and more about the feeling of it.
And that rounds up our look at how to use the three exposure controls creatively for our photography. Now I would like to hear your thoughts, did this help you? Did you get some ideas as to how you want to use the exposure controls creatively in your photography? Is there something you felt was lacking? Please let me hear from you.