How to make the most of high ISOs
October 12, 2018
1. Avoiding the shakes
As a travel or location photographer, you have to make the most of the light conditions that you encounter, and can often find yourself shooting in gloomy interiors. There are many places where using a tripod is not allowed or not practical, or you might not even have taken one on your travels. If you increase the ISO, your camera will need less light to achieve a correct exposure and you can therefore use a correspondingly faster shutter speed, so you can handhold without camera shake in these low-light situations.
2. It’s not just about the shakes
Increasing the ISO is not just about avoiding camera shake: it is a creative tool, allowing you to use the shutter speed or aperture that you want, and you should get into the habit of adjusting it in the same way that you might adjust the shutter speed or aperture. Increasing the ISO by two stops might make the difference between a lacklustre 1/500sec and a motion-freezing 1/2,000sec. It can also be used to give you a couple of extra stops of aperture – significantly increasing the depth of field.
3. Be reasonable about what you can achieve
If you have an older camera, or a compact or bridge camera with a smaller sensor, then you probably won’t have very good high ISO performance. You will also struggle to compete with expensive professional cameras that will cost many thousands of pounds. Bear this in mind, and don’t be too critical of your pictures just because of noise. This will be generally less of an issue in your pictures than obvious camera shake. Don’t be too self-critical. You might be able to zoom your images to 100% on a large computer monitor and see every blemish, but unless you print massive sized images, or crop to a tiny portion of the frame, it is very unlikely that anyone else will ever see the images at such large magnifications.
4. Avoid Auto ISO
Many photographers avoid using Auto ISO. If the shutter speed drops below a certain preset, the camera will increase the ISO to compensate. It won’t help you to increase depth of field, or to force a super-fast shutter speed, though. It will also work against you if you try to quickly select a slow shutter speed for panning. Switch this function off and regain control over your camera settings.
5. Understanding the numbers
ISO is essentially the same scale as the old film ASA sensitivity scale – although unlike film, the superior ISO performance of modern digital cameras means that the numbers can be huge! Each doubling or halving of the ISO scale represents a doubling or halving of the amount of light needed to correctly expose the picture – which is defined in exposure terms as a stop. This increment is the same as a doubling or halving of the shutter speed, and each whole increment of aperture. This means that if you increase the ISO by two stops, you can correspondingly increase the shutter speed or aperture by the same amount.
As the scale involves doubling of numbers it only takes ten stops to get to six figures, but the difference between ISO 56,200 and ISO 112,400 is the same as the difference between ISO 100 and ISO 200.
6. Versatility of digital
Digital photography offers incredible versatility. Not only can you increase the ISO sensitivity to levels that were totally impossible with film, you can usually do so in increments of 1/3 stop and on a shot-by-shot basis, depending on the subject and the lighting conditions. You don’t have to make massive changes to the ISO: sometimes just increasing it by a stop can be enough to make a difference.
7. Avoid underexposure
Your camera only has one, native ISO. If you select a higher sensitivity then the camera will underexpose by the commensurate amount, and compensate for this in the camera software. Whenever you underexpose and lighten in processing – whether in-camera by using a higher ISO or by messing up the exposure and lightening in post-processing – then you will get noise on the image. If you underexpose at a higher ISO then the combined effect of the noise is magnified!
8. Use noise reduction
You can reduce high ISO noise with software noise reduction. There are some bespoke products such as Topaz Denoise or Nik Dfine, or you can simply use the noise reduction in Adobe Lightroom. Drag the Color slider to reduce the random colour pixels of chroma noise, and the Luminance slider to reduce the grainy, grey speckling of luminance noise. Zoom to 100% to assess the results. In both cases, the Detail slider controls how small details are preserved. If you apply much Luminance noise reduction, then you will have to increase the Sharpening slightly in order to compensate for the overall softening of the image.
9. Drawbacks of high ISO
Most people are familiar with high ISO noise: the grey, grainy speckling of luminance noise, and the random colour pixels of chroma noise; however, if you shoot at higher ISOs you will also have a lower dynamic range. This is the ability of the camera to handle contrast. A diminished dynamic range can mean that shadow details might be lost, or highlights blown in very contrasty conditions. While you shouldn’t worry about increasing the ISO, you should always try to shoot with the lowest ISO possible for the best-quality results.
10. Improve your technique
Avoiding camera shake is not just about using a high ISO to increase the shutter speed: if you improve your technique then you can keep the camera still at a lower setting. Use noise reduction on the lens or camera body if you can, brace yourself against something like a wall or pillar, and squeeze the shutter release gently. Last, take a few shots in quick succession: essentially bracketing against camera shake.
11. Use auto assist for focus
In low-light levels your camera can struggle to focus. Many have a focus assist light to help, to ensure your shots are sharp. This will often only work if the camera is set to a single, rather than continuous, focus mode.
12. Avoid imaginary numbers
Camera manufacturers often exaggerate the higher numbers, and if you try to achieve these numbers there is a good chance that you might crash and burn. Many cameras have an extended range on top of the numbered ISO settings. These are often unusable in anything but images that will be reproduced very small indeed. My rule of thumb is that I never use the extended range of ISOs and try not to exceed a stop lower than the highest numbered ISO.
13. Bracket for noise
If you are not sure about what maximum ISO you can use, take the same shot at a couple of different ISO settings, then select the one at the lowest ISO that works – whether that means the one without camera shake or the one with the adequate depth of field. This means that you will have the best-quality shot, with the lowest amount of noise possible.
14. Increase ISO with flash
It is often said that you should avoid higher ISOs when using flash, but an increase in the ISO will, in effect, make your flash more powerful: enabling it to light up subjects that are further away or allowing you to use a smaller aperture. If you combine the slow sync flash setting with a higher ISO, then the ambient light in the image can be balanced with the flash.
15. Pack a prime
Sometimes the light levels will be so low that even when using your highest ISO you still won’t be able to select a fast enough shutter speed. In these instances, use a fast prime lens. A 50mm f/1.4 lens will allow two stops more light into the lens than even a fast professional zoom lens with an aperture of f/2.8. This could make the difference between a usable shutter speed of 1/15sec and an unusable 1/60sec.
16. Use a wideangle lens
A telephoto lens doesn’t just magnify the image size – it magnifies camera shake. If you are shooting an interior in low light, a wideangle lens will show less camera shake at a given shutter speed. It will also display a greater depth of field at a given aperture than a telephoto lens. This enables you to take pictures without having to use such a high ISO that the image quality is degraded.
17. Beware of shadows
Your pictures will show more noise in the shadow areas than in lighter parts of the picture. If there is necessary detail in shadow areas, then you should try not to use such a high ISO as when you are shooting lighter-toned subjects.
18. Avoid subject blur
Even if you are capable at handholding your camera at slow shutter speeds you might still get blur from a moving subject. Sometimes this can be a welcome creative effect; other times it can ruin your pictures. Even when you’re shooting an indoor portrait, a move of a head can still blur the picture at very slow shutter speeds. Select a shutter speed a couple of stops faster than your slowest handholding speed to prevent this blur: increasing the ISO will allow you to do this.
19. Test your limits
The maximum usable ISO will depend on your camera, the subject matter and the tolerance to (camera) noise. The only way to assess it is to take a range of shots of the same subject at different ISO settings and then view the results on a computer. Work out where your personal limits are: the ISOs that you can comfortably use, your highest usable setting in normal conditions, and the maximum ISO that you would use at a pinch, if you have to. When you are editing your pictures, overlay the metadata so you can see what the camera settings were. This will let you assess your highest usable ISO, and see what shutter speeds will give you camera shake and subject blur.
20. Shoot raw
If you shoot in the JPEG format, then the camera will apply preselected noise-reduction settings. If you shoot using the raw format, these settings will be applied to the JPEG preview of the image, and you can adjust the noise-reduction settings retrospectively. This allows you to walk that fine line between not enough noise reduction, and too much, which can make the image appear soft.