The ISO Value in Photography
The ISO value of your camera is one of the three most important camera settings in photography. It can significantly affect the look and feel of your photos. What exactly is the ISO value, and how does it affect your photos? It’s a good thing that you are a photography beginner. A fundamental first step. In this article, I will explain what ISO is and how you can use it effectively to get better images with your camera.
What is the ISO value?
ISO values of your camera
The ISO value is specified at different levels. For most cameras, the lowest ISO value is 100, but there are some that start at 50. Each camera has a varied ISO range (sometimes called ISO sensitivity) that you can use. The value you set then doubles, resulting in a series with the sequence:
- ISO 100 (low), 200, 400, 800, 1600, 3200, 6400 (high)
In simple terms, the ISO value affects the light sensitivity of your image sensor (the full explanation is a bit more complex). The higher the ISO value, the more sensitive the image sensor becomes. At higher values, less light needs to fall on the sensor, and you still get a correctly exposed image. The opposite is, of course, true for low ISO values. As a result, the ISO value can be beneficial when shooting in a dark environment. You can also be more flexible in adjusting various other settings, such as shutter speed and aperture.
The meaning of these numbers is straightforward: if you double the ISO, the brightness of the image doubles. An image with the ISO 400 is, therefore, under otherwise identical conditions, twice as bright as an image with the ISO 200. But at some point, this is over. In the picture opposite, you can see how much the image changes when you increase the ISO from 200 to 1600.
Are high ISO values better?
The reverse is the case. An increase in ISO always has consequences. A photo with a high ISO value contains a strong grain, which is called “image noise”. An image with excessive noise may not be usable. Lightening an image by increasing the ISO setting is, therefore, always a compromise. If possible, you should always try to slow down the shutter speed or open the aperture further first to adjust the brightness and get better results. Unfortunately, this is not possible in some situations. For example, when an object becomes blurred due to longer exposure times. More about this later.
ISO definition in photography
The abbreviation “ISO” stands for “International Organization for Standardization”. However, the ISO of the camera does not directly refer to this organization, which creates various standards in technology and research. Before the ISO value, there were two other standards: ASA and DIN. In 1974, these were merged into the ISO standard. Although the ISO standard originally only defined film speed, it was later adopted by manufacturers of digital cameras to maintain similar levels of brightness to film. This standard has since been used in both photography and videography. Have I aroused your interest in the history of photography or videography?
Which ISO value to use when
Many photographers basically know what the ISO is. However, they are often not sure of which ISO value to choose when taking pictures. In practice, there is a reason why a camera allows so many ISO settings: Different situations require different ISO values. Below you will find some scenarios that you might come across. First, a very simple overview of the ISO value table, which you can easily remember.
| Time of Day / Light Type | ISO Range | Recommended ISO Value* |
|---|---|---|
| Bright / normal daylight | Low | 100 – 200 |
| Overcast sky / twilight | 400 – 800 | |
| At night or in dark interiors | High | 1600 – 6400 – High ISO |
*Each camera is different, you should just try it best, it’s the only way to learn.
As a little tip from me: If you’re still unsure, just use the auto mode to see how your camera estimates the ISO value itself.
Auto-ISO
Most cameras have an auto ISO setting, which usually works well in low light environments. The beauty of this setting is that you can enter the maximum ISO value you want to use. The camera will then not exceed this limit. I set my maximum ISO to around ISO 800 or 1600 when I want to limit the noise in a photo. The disadvantage is that the camera will use increasingly slower shutter speeds when it reaches this ISO limit. This, in turn, leads to more motion blur. So in that sense, everything is a compromise, and you should check your pictures on the LCD continuously, not that the big surprise follows at home.
A high ISO is not always inevitable
Even though it is better to use a low ISO, sometimes you can’t avoid increasing the ISO value. In many cases, it is also necessary to do so to take a usable image at all. The simple reason is that you often struggle with motion blur. That means long exposures are not an option; otherwise, everything would be blurred. So you are forced to choose between a sharp photo with high ISO or a blurred photo with low ISO. Take a look at the following picture.
This image was taken at ISO 4000 and is therefore somewhat grainy. But what would the picture have looked like if the photographer had taken it at ISO 100 with the slower shutter speed (for example, 1/50 second)? A photo taken with these settings would have brought a lot of unwanted motion blur. In short, the photographer would have ruined the image.
The Bottom Line
The bottom line is that you should increase the ISO if there is not enough light for the camera to take a sharp, bright photo in another way. When I’m shooting indoors without a tripod and without a flash, I always set the ISO sensitivity to a higher value.
Image noise
As already mentioned before, a photo with a high ISO-value causes a so-called image noise. The higher the ISO value, the more likely it is that the photo appears grainy. This grainy effect is also called brightness or luminance noise that is recognizable from approximately ISO 400. Despite the noise, the picture can still be sharp and correctly exposed – or have the right brightness. Most photographers prefer a somewhat grainy and sharp image rather than a dark and blurred image. Besides, the noise can be reduced later during image processing with a graphics program such as Photoshop, Lightroom, or CaptureOne with filters.
ISO Myths and Misunderstandings
The ISO is the sensitivity of the sensor
This is the most common myth associated with ISO. You can find it everywhere on the Internet and in books. Although it can be helpful to think of ISO as a kind of sensor sensitivity of the camera, in reality, this is not the case. Instead, digital sensors have only one sensitivity, regardless of their ISO value. Correctly, ISO is a factor to tell your camera how bright the output photo should be at a given exposure.
The ISO is part of the exposure
No. The ISO is not part of the exposure. Shutter speed and aperture brighten your photo by allowing more light to reach the sensor depending on the setting. The ISO, on the other hand, does not do this. Instead, it brightens the already taken photo. So ISO is not part of the exposure.
The ISO and brightening in the post-processing are the same
This statement must actually be accurate, according to the previous statement. So it is a smart question – but also here it is merely a misunderstanding. Lightening a photo in post-production can be done in many ways, similar to increasing the ISO value. However, the noise is more visible when brightening in post-processing. The simple difference is that increasing the ISO value in the camera almost always produces better image quality than brightening a photo in post-processing. In other words, it’s better to use ISO 800 if necessary than to brighten an ISO 100 photo to a high degree with photo software.
ISO in Analogue Photography
In analog photography, you don’t have the luxury of setting the ISO light sensitivity directly on the camera. The photographer must know the lighting conditions in advance in order to load the right film with the appropriate sensitivity. In addition, he must also decide whether to use color or black-and-white film. That costs a lot of flexibility. If the weather changes or the lighting conditions change significantly, the film would have to be adjusted and replaced. By the way, what is now called ISO was formerly called DIN (German Institute for Standardization) or ANSI (American Standards Association). The two standards were combined together to form the ISO unit.
Summary
If possible, always shoot with the lowest ISO value your camera allows – the base ISO (50-10).
Then control the exposure with the aperture or shutter speed.
Increase the ISO only if you want to freeze a fast movement and therefore have to set a short exposure time.
