The ISO setting is the odd one out in the exposure triangle and in some ways the most outdated and less important setting. In the future, I think it will be replaced by a gain dial or some other way to better suit the needs of a photographer.

‘generally, the more expensive professional cameras produce less noise at higher ISO levels.’ – AP magazine

With this in mind – this blog hopes to explain what ISO means to a photographer and how to best use the dial on your camera to get the best images you can.

Film Cameras & Digital Cameras.

Iso is the only setting linked to the Exposure Triangle that changed during the move from film cameras to digital cameras.

Or to be more relevant, the ISO dial is the most effected dial on a camera during the move from analog to digital. When digital sensors replaced rolls of film, nothing else really changed regarding how cameras work. We still have aperture settings, shutter speed settings & different focal lengths to work with. In the past, we would have to change the film to increase the sensitivity, but now we have a dial.

Above: An example of an image with grain/noise

The higher the number, the more boosted the digital signal is from the sensor. Boosting the signal, just like with audio speaker or microphone – increases static or noise – in other words, increasing the sensitivity will increase the static just as much as the signal we are trying to capture. This is visually apparent as a loss of quaily in an image.

Back in the film days – the fastest film commonly available was 3200 for B&W or 1600 for a colour image. Most photographers using digital cameras today are happy to shoot up into the higher settings with no problem. It is very hard to compare film to digital. But, from my own experience, we are way past the argument that film is better in terms of quality of image when looking for detail using like for like lighting settings. This is not to say which is better – in the right hand’s film cameras can give awesome results going up against the most recent cameras today.

With the advancing technology moving forward, working with higher ISO’s has become less or a worry. When I first started shooting I would do everything in my power to avoid going above ISO 800 due to a total lack of image quality. The above image shows a cut away from two images – one at 200 ISO and the other boosted to 12800 iso in Camera.

Interesting – I tried a quick experiment. Knowing that the ISO adjustment is just boosting the signal/sensitivity of the sensor. I took two images. One at the base (iso 200 on the X-Pro2) and one at 12800. The image at iso 200 was dark, as expected, but then I boosted the full amount Adobe Lightroom give. This is what we mean by ‘post-produced’ as we are appliing effects after the camera stage.  Both images captured in RAW.

Above: ISO 12800
Below: ISO 200 – adjusted in Adobe Lightroom to match exposure

Below: the same image photographed at ISO 200.

From this very quick test, it seems very clear that the technology and processing in camera is having a better final outcome than just adjusting the RAW files after. It seems like getting your ISO right in camera is going to give you a better and cleaner final image if you are working the camera, not just using post-processing tools to rescue files.

What does Noise look like?

Shooting the lowest possible ISO is the way to go. We can make adjustments using the exposure sliders after we can take the images in post-processing but with less quality than using the camera ISO dial. Digitally boosting the images will increase the amount of ‘noise’ in the image, but that is a trade-off for having a faster shutter speed or aperture setting that we wish to use.

From AP magazine – 20 tips n using ISO.

The Shutter Speed dial, Aperture Speed dial, and ISO dial are used together to balance out the settings for an image/exposure.

ISO is the only setting that does not artistically control any part of an image. It only adjusts how sensitive the sensor is, letting us have more freedom to use different shutter speeds and aperture settings. However, from personal experience, I have found that as the noise increases, the colour becomes less saturated and texture becomes softer.  The unedited image below was produced at 2000 iso. Normally using flash I would never use an ISO rating this high. Due to the amount of noise, the image seems a little soft with the hair and skin looking waxy.

This image of Roseanne was taken using the same lighting style but at a much lower (ISO 200). It’s clear to see the difference. Look at the sharpness in the hairlines with how well the camera copes with the skin texture.

Is ISO linked to Dynamic Range?

Shooting your LOWEST ISO is always my main thought while setting up the camera. Getting this right is the very best way to get the most out of your camera.  This sunset (below) was photographed at ISO 50 on a Hasselblad 500C. Shooting the lowest ISO will give you the best flat out the start, and as you increase the ISO you will see colours change, become less vivid and less contrast. It is said that the range its- self is not linked but, you do seem to get a different range of colours. What do you think? Try your own tests. Remember the ISO values are not constant across brands, cameras or any listed spec sheet.

Shooting this image at iso 50, I was getting the best the camera could do in terms of sharpness, colour, contrast and all-out performance.

When to Use Low ISO

I might be wrong, but I would say always use the lowest ISO you can. This sometimes might be quite high as you should always give priority to your shutter speed and aperture settings as they control what your image is going to look like. Using Tripods and adding lighting are always going to be preferable to shooting higher ISO’s if I can.

If you are planning on doing any sort of post-production, shooting the lowest ISO becomes even more critical. Retouching becomes harder the less you have to work in the first instance.

  • Landscape
  • Beauty
  • Advertising
  • Commercial
  • Wide Range of colours
  • Vivid Colour
  • Smooth Tones

What ISO Should You Use?

The lowest you can without having to introduce motion blur with your shutter settings.

Auto ISO – Good or Bad?

In many cameras, you can use an Auto ISO setting. The Fujifilm cameras have a range of settings you can pick from to limit the range of auto settings that the camera will use.

When is an image to ‘noisy’ & When to Use High ISO

I have and do use my full range of given ISO’s in the camera, then sometimes boost them, even more, using tools like Photoshop or Lightroom.
Images like this one (below: Bowling for Soup) taken at 1600 are very common these days but would of been very risky even a few years ago.

Super high ISO shots are great for when you have fast moving subjects in a very low light area. With this image of Patent Pending, they are moving about quickly in a very dark red light. Boosting the ISO and using a fast lens was the only way to be able to have a fast enough shutter speed to avoid motion blur.  This image is taken at 12800 iso but had nose reduction applied in lightroom.

Sometimes shooting high ISO’s can be used to create an effect – such as with this image of Ryan, Rob & Micky. We are using all the elements of distortion and degradation given using higher iso to provide the look in the image.  ISO 2500.   

In short, we all have to set our own levels of the image we are looking to create, however, I would say that using the lowest ISO you can is always the best idea – unless you are trying to use the higher ISO to capture the noisy gain, like in the image above.

The short version…..

ISO is linked to both Shutter Speed and Aperture – using this equation.

  • H=E x T
  • (H) Exposure = irradiance x time

Irradiance (E)

  • Amount of light falling on a unit area of a sensor per second (measured in lumins)
  • Controlled by the Aperture

Exposure Time (T)

  • in Seconds
  • Controlled by the Shutter

ISO only comes in to play when the result of this equation ( you set the aperture and shutter speed ) hits the sensor.

Fun Facts via Wikipieda.

  • The ASA and DIN film speed standards have been combined into the ISO standards since 1974.
  • The ISO standard ISO 12232:2006 gives digital still camera manufacturers a choice of five different techniques for determining the exposure index rating at each sensitivity setting provided by a particular camera model.
  • Digital cameras have far surpassed film in terms of sensitivity to light, with ISO equivalent speeds of up to 4,560,000 (Canon’s ME20F) with the Nikon D5 having an ISO of 3280000.
  • Some high-speed black-and-white films, such as Ilford Delta 3200 and Kodak T-MAX P3200, are marketed with film speeds in excess of their true ISO speed as determined using the ISO testing method. For example, the Ilford product is actually an ISO 1000 film, according to its data sheet. The manufacturers do not indicate that the 3200 number is an ISO rating on their packaging. Kodak and Fuji also marketed E6 films designed for pushing (hence the “P” prefix), such as Ektachrome P800/1600 and Fujichrome P1600, both with a base speed of ISO 400.


This blog is part of the EXPOSURE TRIANGLE blogs.

Find the links to the other two by clicking the images.

Extra reading – Marc Levoys lectures are very intense, but if you are looking for a more technical explanation of how photography works and the maths & equations behind it check out this link for a full comprehensive set of lectures.