Camera Basics #03 - What is ISO sensitivity? Everything you need to know!
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ISO is one of the core elements of photography. If you understand ISO, you can work much better with the light in many situations and can also use ISO noise as a stylistic device for your photos.
Beginners in particular come up against the sacred values when starting out in photography:
- Aperture
- Shutter speed / Exposure time
- ISO
- Exposure compensation
Dual ISO of the Panasonic Lumix S5iix - ISO 6400 | Terobes ArtsDual ISO of the Panasonic Lumix S5iix - ISO 6400How ISO works in digital cameras
Modern cameras, such as system cameras and SLR cameras, have a sensor on which they capture images, which are now equipped with ever-improving algorithms to reduce ISO noise, because ISO as it once existed in analog photography is no longer the same. You can simply set the ISO in the camera without having to change the film. Nowadays, much higher values can be achieved with very good results. Digital cameras can sometimes go up to an ISO of over 120,000.
Nerd details about digital ISO
In digital photography, the ISO is only a value that is influenced by the software; some sensors can actually be adjusted in an analog/real way. In principle, the ISO in a digital camera is fed from an analog signal into an analog/digital converter, where the signal is then amplified by adjusting the ISO. With new sensors, manufacturers create new methods for reading out the sensor, which voltage gives you better results, i.e. lower noise and higher image quality. This means that sometimes the intermediate steps in the ISO result in more noise than the next higher value.
Analog photography and film speed
In analog photography, you couldn't tell a sensor how sensitive it should be; then as now, this was determined by the film speed, which is why analog films have the ISO specification so that the photographer can work and the film is easier to use in dark situations. You could also say that the ISO was a value for the light meter.
Why is ISO called ISO and not DIN?
ISO stands for International Organization for Standardization. This organization unites national standardization organizations from different countries. However, before ISO became established as a standard, different national abbreviations were used for the sensitivities of films. In the past, for example, you could find information such as "DIN" (German Institute for Standardization) or "ASA" (American Standards Association) on old films.
With the introduction of the international ISO standard, film speeds are now specified uniformly worldwide. This not only facilitates communication between photographers from different countries, but also ensures consistent measurement and comparability of the speeds of different films and cameras.
ISO 2500 in Tokyo at night | Terobes ArtsISO 2500 in Tokyo at night | Terobes ArtsAdvantages and disadvantages of high ISO values
We will now look at the advantages and disadvantages of a high ISO value.
Advantages of a high ISO
- Faster exposure times possible
- less camera shake in shots
- Image noise can be a stylistic device
Disadvantages of a high ISO
- Image noise
- Sharpness decreases
- Colors are distorted (color pixel errors)
Using the right ISO value
In practice, this means that a high ISO value is particularly needed in dark lighting situations or when we want to work with a closed aperture or a very fast shutter speed.
low ISO
high ISOIncreasing the ISO helps to shorten the exposure times.
ISO values for different situations
Below we present a few ISO values that you can use as a guide to help you achieve great results faster.
- ISO 100-200, in bright daylight situations with light cloud cover. At the sea or in the mountains you can use a rather low ISO.
- ISO 400-800, in foggy situations, in shadow or forest situations, but also in well-lit interiors. For example, an ISO of 400 is suitable for taking photos in rooms with lots of window light.
- ISO 800-3200 at twilight or at night when photographing stars. Or when taking street shots in the city at night.
- ISO 800-6400, for interiors such as a registry office or discotheques and depending on the exposure time you choose.
Important information in passing: some cameras are not able to set an ISO value of 100, as these cameras then have a higher base ISO. However, this is not a problem with digital cameras.
ISO noise in video
The ISO is to be understood here more as a gain, as with audio, there is always a background noise, so you can amplify the signal, but if there is not enough light, then noise is lost. What is important is the signal-to-noise ratio, where the signal should be significantly greater than the noise, i.e. there should be enough light, because as soon as the noise is greater than the signal you can no longer use it properly.
By increasing the ISO, the value or ratio is now improved and content in the dark is now more visible, but the noise now also increases over the entire image, as the background noise increases, but this lowers the overall dynamic range, so it is better to film the dark areas with a lower ISO, adjust the aperture or adjust the exposure time. Of course, it would be effective to add another light to fill the room with light.
Dual ISO
Dual ISO essentially combines two different ISO sensitivities on a single image sensor. The pixels are divided into two groups, with each group having a different ISO setting. Typically, this is a low ISO for one group of pixels and a higher ISO for the other.
This method allows cameras to capture a wider range of exposure information when taking photos or videos. The result is improved dynamic range and reduced noise, especially in the shadow areas of the image.
For photographers, dual ISO means that they can achieve better results in situations with extreme lighting conditions, such as strong contrasts between shadows and highlights. The technique makes it possible to better preserve details in both dark and light areas of an image, resulting in more balanced and higher quality shots overall. However, it should be noted that not all cameras have dual ISO capabilities and implementation may vary by manufacturer and model.
Nerd details about dual ISO
The dual ISO works on the principle that two capacitors are installed, which have a different capacity, whereby a smaller and a larger capacitor work. The photon noise does not change, but the readout noise (not dark noise) decreases slightly.
Two small tasks for you:
- Take a series of pictures with a low, medium and very high ISO value. Observe how the exposure changes and zoom into the image so that you can see the differences in quality
- Find out the maximum tolerable ISO value by taking photos in a dark environment with increasing ISO values. Check the photos on the computer and find out when the noise becomes too strong (for you).
Information about this article
This article is a new edition of the old article, so that it meets the requirements of our readers and the technical subtleties and nerdiness that we do not want to withhold from the community.
Thank you for reading this article. If you are interested in other photography basics, then take a look at the other camera basics. Let's continue with the white balance
Camera Basics #04 - What is the white balance?
What is white balance good for? If you've ever stumbled across this setting on your camera but don't know what it does, then this article is for you.
The white balance
