Technocrat Tuesday: Noise - Or dottyity dot

Technocrat Tuesday: Noise - Or dottyity dot

Last week, we touched on Noise and what it can do to an image. So what is noise?

In film cameras, silver grains are used to collect a density of darkness of how an image can come out. To allow more light to be captured, bigger grains are used. Hence the term "grainy" is used

For Digital images, the same pretty much occurs. larger clumps on pixels work together to capture more information. The net result is noise.

Noise can be related to ISO speed in digital cameras.

See the strip above mentioning from 100 ISO up to 3200 ISO

As you can see, the strip gets more noisy as you go along.


How do you prevent noise?

Shoot in perfect daylight. Right. That isn't going to happen..

My advice:
If you're buying a camera, check it has ISO adjustment on it (this will allow you to control the amount of noise and light)
If you haven't, experiment with the settings. There's normally and evening/night setting on most digital cameras
Through Experimentation, you'll find some settings you can work with eventually. For example if you take an image at 100 ISO at night... be prepared for the result. Try 400ISO or 800ISO and see what happens. I tend to shoot 800 ISO at night, 100 during the day, and 200 ISO if it gets grey.
Use auto correction where possible - it can bring out the highlights you may have missed.
And remember to set the ISO back to where you normally have it for daytime shots!


If it gets bad, consider using Noise Ninja or Neat Image to reduce the amount of noise in an image. I've had some pretty good recovery shots using this software. It goes without saying make sure you have good backups of everything before experimenting with this sort of product.

So some more examples of noisy images with solutions and other things

Two examples: ones on the left are before: ones on the right after after. Notice the images on the left are very dotty. Using a tool called NeatImage fixed them.