The Keys to Minimising Noise in Your Photographs

By Light Stalking on 5 Sep 2010 in Guides, Post Production, Shooting[ 10 Comments ]

One of the largest problems many folks have with digital photography is the amount of noise that ends up in the final image. Noise basically presents itself as graininess or speckles, usually most recognizable across larger areas of uniform colour such as sky. While sometimes it is a desirable effect such as in some of the photos below, often you will want to minimise it. The bad news is that there is no perfect solution to noise problems, but the good news is that there are things you can do to reduce, and in many cases, eliminate noise in your photographs.

Photo by Stuck in Customs

What Causes Noise?

Truly knowing how to reduce or eliminate noise is better served by knowing what causes it. In photography there are several causes of noise.

The first scenario is that image sensor heat can increase enough to stimulate electrons (“Thermal Noise”). These superfluous electrons then get mixed in with the “true” photoelectrons that are the real target of our image sensor. The analog signal (which is converted to pixels by the sensor) is therefore contaminated before it even gets to that point.

In some situations the above scenario can cause each of the photosites on an image sensor to generate superfluous signals which can then contaminate the neighboring photosites. On smaller image sensors which cram more photosites into a smaller area, this effect can be magnified.

Another common cause of noise is shooting at higher ISO settings. As these settings basically magnify the light signal, they also magnify other unwanted signals such as background interference (eg. heat sources). When you are photographing an area of low light, the background signals can be strong enough to compete with the signals from the limited light of the area you are shooting.

Photo by GoldSardine

What Can a Photographer Do About Noise?

As with anything, photography presents us with a series of compromises when it comes to solving the problem of noise. Here are some of the more obvious things you can do to reduce noise in your images.

Shoot At a Low ISO – It’s a simple one, but if the situation will allow it, then turn down the ISO. Reducing the sensitivity of the sensor reduces the chance that it will pick up unwanted interference.

Reduce Shutter Speed – This simply reduces the chance that unwanted signals will get mixed in with the ones you really want to capture. Again, it’s really only a solution if the shooting conditions allow for you to reduce shutter speed.

Utilise the In-Camera Noise Reduction Feature – Most DSLRs come with an in-camera noise reduction feature. In many cases this does a fine job of reducing noise during image processing. The downsides to this are that the processing time of the image is often increased (sometimes by many seconds) and there can also be loss of finer detail in the shot.

Don’t be Afraid to Use Post Processing – There are several pieces of dedicated software available to digital photographers with the sole purpose of reducing noise in your images. Many people recommend noise reduction software as an integral part of any photographer’s arsenal. You can also utilise noise reduction techniques in other software such as Photoshop, GIMP or Lightroom. Some tutorials you might be interested in include:

Keep Your Camera Cool – This one is often overlooked, but many people report that simply keeping your camera cool (or at least out of hot storage areas) immediately before a shoot can have a significant impact on improving noise in photos. The idea here is to minimise electrons that are stimulated by heat on your sensor therefor reducing contamination in the signal.

Photo by Centrifuga Teatrante

Noise is simply one of those challenges that photography throws at us from time to time that make it challenging to get that perfect shot. With a little forethought it’s easy enough to account for it and continue the chase!

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10 Comments

+1 Chris Gin:

A couple of things:

1) In-Camera Noise Reduction Feature. This doesn’t help with regular noise as such, it only helps with ‘hot spots’ that are caused by the overheated pixels on the sensor. These are very easy to clone out so I think it’s better to leave this feature disabled.

2) A major cause of noise is underexposure. This can happen when trying to reduce the exposure to avoid blown highlights as the shadows then end up underexposed and noisy. Or simply the whole photo was underexposed for some reason. ‘Exposing to the right’, where you push the histogram as far right as possible without clipping highlights, helps minimize noise but means the image may look too bright on the LCD.

September 5, 2010 at 9:32 pmReply
Anthony:

great!

September 5, 2010 at 10:56 pmReply
Anthony:

http://abayarong.files.wordpress.com/2010/09/smile.jpg?w=950&h=570

September 5, 2010 at 10:59 pmReply
David:

I think the in-camera noise reduction feature is useless for people photography as it takes way too long for my taste. It’s okay for landscapes and whatnot where you have more time.

September 6, 2010 at 7:45 amReply
Peter:

Of course, it is not the case that we always WANT to reduce noise. There are plenty of situations where it adds a nice touch to the photo.

September 6, 2010 at 6:41 pmReply
Trevor Rideout:

Hey Chris… You beat me to it.

Exposing to the right is far better than underexposing your shot. Not only for reducing noise, but also because there is more information retained in the file on the right hand side of the histogram. In post, it is much easier to bring an exposure back down a stop. If you clip the blacks, you won’t get them back

September 9, 2010 at 4:23 pmReply
Jay mcintyre:

Lightroom 3 all the way! Best noise reduction I’ve used.

September 9, 2010 at 5:39 pmReply
rich:

In-camera reduction as well as reducing noise via PS PP, while helpful to a degree, both suppress sharpness and clarity, a critical loss for prints. Best if possible to use a lower ISO, wider aperture, slower shutter and a tripod. Then too realize that depending upon the camera you are using, the sensor may not be capable of properly capturing enough light, or the lens may not have enough glass; e.g., an 17-40 F4 will not unless pushed by the techniques listed, do as good a job as a 50 F1.2 and even then the faster glass will always do a better job, especially when the image is cropped. Problem is the cost.

Nice article LS.

October 31, 2010 at 6:29 amReply
May Tove:

Shooting in RAW will give more room for getting details back that seems burned out when the tecnique “overexposing” is used (together with lowest ISO)

For Nikon “Raw” (NEF-files), the best program to handle this, is their (Nikon’s) own program Capture NX2. (Also the best program for noise reduction and sharpening).

I also want to thank for all the good articles in here.

July 13, 2011 at 1:51 amReply
cmrazon:

nice article….

October 12, 2011 at 5:04 amReply