Know more about noise

You all know that one of the things you need to deal with when shooting photos, is noise, writes Jon Adams & Andrew James. The term noise is a strange one really since you can’t hear a photograph –  so why is this the phrase used to describe something that looks like speckling and can soften the overall clarity of your image?

Any electronic equipment that records stills, videos, or audio, is fighting to provide you with as perfect a picture or sound as possible. A lot of the time we don’t even think about it because the gear you’re using is seamlessly translating the signal it receives – light or sound waves – into crisp images or pure audio files.

But if you start making the task more difficult by reducing the level of the light or sound you want to capture, you’ll soon run into the attacker in this war – noise. You will all have come across it, and as we stated, it looks like grain that potentially spoils the sharpness and general appearance of your images.

If it makes it easier to think of it in audio terms, then it sounds like hum or hiss. The important thing to remember is that this noise isn’t part of the signal you’re trying to shoot or record; it is simply electronic interference generated by the recording device. The simple fact is, cameras, microphones and digital recorders are full of electronic components. When everything is working hard, it just can’t run silently.

If the signal you’re recording is good – in other words it’s strongly illuminated or loud, then the noise is overpowered so it’s invisible or inaudible. But if the signal is weak, then when you boost the sensor’s sensitivity by increasing ISO, the noise also gets boosted to the same degree, and it becomes visible, potentially to the point where you throw your arms in the air because the detail in your photo is ugly and you feel its visual appeal has been reduced.

Above: The ugly speckled appearance of noise on a shadow area of an image.

A major factor in camera noise control is sensor size. The larger sensors in full-frame cameras have bigger photosites than their smaller counterparts (assuming the same pixel-count). It’s a simple fact that bigger photosites boast greater light-gathering ability, so you get more signal and less noise. This is partially why certain cameras handle the noise generated at higher ISOs better – their larger sensors are just better at collecting the available light.

The good news is, that ALL relatively new DSLRs and mirrorless cameras are better at dealing with noise than the early models that appeared in the first decade or so of the digital camera revolution. Back in those days, heading above ISO 400 was considered risky and only to be attempted by the brave or the foolhardy. But it remains a fact that some cameras (or rather sensors) are better at noise control than others.

Above: Sometimes you have no choice other than to shoot at a higher ISO to get a shutter speed you can work with. In the case of this osprey shot – it’s ISO 3200. The full-frame sensor in the 1DX (original not more recent models), was able to handle the noise issue very well, although it’s been helped by how the image was shot. There is no noise-reduction processing in this image. 

How much noise control matters to you depends on several things. Firstly, what you shoot. If you mainly shoot landscapes from a tripod, it’s unlikely you will worry too much about it. Secondly, we all have a different view of the aesthetics of noise. For those who love zooming in and staring at the pixels, noise is perhaps a bigger issue that it needs to be. Stare at anything close-up for long enough and you’ll find fault! Thirdly, if you are quite happy to ‘process out’ some of the noise in Photoshop, Lightroom, or with plugs-in like Topaz DeNoise, then again, perhaps you can live with a camera where higher ISO means lots more noise. And fourthly, if you are really sensible, you’ll think that actually noise is really more of a worry to the photographer than the viewer.

What we are saying is, the amount of noise that’s acceptable in a picture is subjective. A good idea is to find YOUR camera’s ISO ‘ceiling’ based on your kind of photography and your aesthetic sensibilities. Next time you’re out shooting a typical scene or subject, after capturing the pic at the default ISO you’d normally use, take a brace of shots at increasingly higher ISOs. You might have to stop down the aperture to keep the exposure within range, but run it as high as conditions will allow so you have an ISO comparison set.

When you’re back at your computer, load them up and find out the highest ISO setting that still gives an acceptable level of detail and colour to YOUR eyes. Whatever that number is – that’s your ISO ceiling – so don’t be afraid to use it when the need arises! You also, shouldn’t be afraid to go over that ceiling too if you HAVE to. It’s always been the Foto-Buzz mantra that a ‘noisier’ photo is better than one blurred by camera shake, simply because you didn’t want to push ISO up.

Over the years, we cannot recall any occasion when an image has been rejected by a magazine because it’s too noisy! Partially, it’s important to remember that when printed, noise is far less obvious than when you zoomed in at 200% in Lightroom, but it’s also a fact that when shooting at high ISOs we’ve taken care to do some simple things to reduce its impact.

Above: This image is zoomed into 200% in Lightroom and there is some noise visible – especially in the shadow areas. But at this magnification you are always going to find something to worry about!

What you do to reduce noise
1 Never underexpose an image when shooting at a high ISO, and then think you can pull detail out of the shadows. You might, but it will often cause even uglier artefacts on the image. Use your histogram to ensure you are ‘shooting to the right’ or as we prefer to call it, simply using the dynamic range available. It’s much better to darken your image in post-processing.

Above: Underexposing a high ISO image and then trying rectify your mistake is only going to end in tears.

Above: Exposing to the right as much as you can, while remaining within the Histogram, will allow you to process your image with the chance of noise degrading image quality hugely reduced. This photo, shot at ISO 6400 has had no image-processing to reduce noise. It’s simply the flat raw outputted as a JPEG. See any noise?

2 Only shoot using as high an ISO as you need. In other words, don’t shoot at ISO 6400 when 3200 will give you an acceptable exposure. This is a good reason not to always rely on Auto ISO, or if you do, limit it to that ISO ‘ceiling’ you have now worked out.

3 Learn some good noise-reduction techniques in the software you’ve used. We’ve covered some of these before and here are some links if you need reminders:

Photoshop Plug-in: Removing Noise with DeNoise Ai & Photoshop

As we see sensors continue to improve, noise will continue to be less of an issue, but whether technology will advance enough to eradicate it completely is another matter. Digital noise, isn’t the scourge it once was and with a little bit of thought and technique, you can keep a check on its impact and keep it at bay.

Published in Camera Skills
  1. Pardon….thought I heard something 😜

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