Parliament reflections on the pavement

Low Light Photography – Noise and Dynamic Range

If you have read my earlier post on low light photography techniques (of course you have), you will have seen a few useful tips about appropriate equipment and techniques. In my next series of posts I want us to consider some elements that can make or break low light photos.

Low light photography, by its very nature, involves longer shutter speeds.

This opens the doors of creativity and presents you with many varied options to experiment with your creative side. Longer shutter speeds bring a couple of potential problems to beware of.

Before I encourage you to unleash the creative genius within, I thought it prudent to look at these issues that, if not understood or catered for, may well thwart your attempts.

Longer shutter speeds bring a couple of potential problems to beware of

So Before we look at some of the creative avenues, lets take a closer look at the potential problems.

Noise Sources.

Noise, if not accounted for, can be a big problem with low light and long exposure photography. Primarily, noise is generally more noticeable in darker areas of your photos

Noise is like grain in the old film days. For those of us who remember film, the higher the film speed the more prevalent grain was in the finished image.

Noise is introduced from two main sources in digital cameras.

The first noise source affecting your photos come from the ISO level or setting.

Some people naturally tend towards setting a higher ISO when light levels drop to keep shutter speeds up. Resist this temptation as it can potentially ruin your creative efforts. Use your tripod if possible.

Image noise example

ISO noise manifests itself as random coloured artifacts – click to see enlarged image

Without getting too technical, higher ISO’s introduce noise into your images as a result of increasing your camera sensors sensitivity.

The cameras sensor is an electronic device and has many millions of receptors that are all electrically charged.

Increasing the ISO increases the sensors sensitivity to incoming light. Unfortunately, the cameras sensor also becomes more sensitive to extraneous electronic ‘noise’ generated by electrically charging all those receptors.

Noise, if not accounted for, can be a big problem with low light and long exposure photography

The second potential source of noise is from the long exposure itself. Normally this isn’t an issue because we usually shoot with shutter speeds in the hundredths or thousandths of a second range. With such short exposures the effects of sensor noise isn’t as easily detectable in images.

With longer exposures however, this natural electrical activity or interference has more chance of being detected and registered.

Don’t get me wrong, there is a place for grain and noise in some elements of photography, but it isn’t always desirable.

To get the best out of your images, and minimise the risk of noise, keep the ISO down to a minimum.

In any case, make sure your camera is set to RAW format. This will give you a better chance of cleaning up any unavoidable noise in post processing. RAW vs jpeg is an ongoing source of debate and I’m happy to write a blog post if anyone wants to delve into that particular topic.

Dynamic Range

The second potential new problem is unbalanced light levels or sometimes called dynamic range.

By dynamic range I mean the differentiation between the brightest and darkest portions of your scene. If the scene has a mixture of very bright and dark elements it could be outside of your sensors operating range.

If this occurs the darkest areas could be totally black and the brightest totally burnt out white.

bright element in night shot too dark

Exposure for the brightest element leaves everything else too dark

bright element in night image overpowers viewer

Longer exposure for other elements means the streetlight overpowers everything else

There are several techniques to try to minimise the effects of unbalanced light levels.

As you can see – neither photo is particularly pleasing.  You could reposition yourself to make sure the bright light is not included in the frame. This would reduce the lit elements to a more manageable level.

Always look out for relatively evenly lit scenes, or if impossible, compose your photo to exclude any extremely bright and dark areas.

Parliament reflections on the pavement

More evenly balanced scene

One technique to consider is bracketing your exposures. Bracketing exposures means taking several images at different exposures.

For example, set camera exposure to f16 for 15 secs, another at 25 secs and a third at 35 secs. One of the exposures may provide an acceptable balance for you. If not, recompose to remove the troublesome dark or light element.

That’s it for technique and potential pitfalls for low light photography, next time I will look at elements that can make your low light images stand out from the crowd.

As usual, thanks for reading this far – I hope you have found something of use. Feel free to leave me your views below

Cheers Gary


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