Saturday, October 23, 2010

Quick Digital Imaging Tip 25/101: Reduce Noise for Cleaner and Also Softer Images

This is tip #25 of 101 digital imaging tips I plan to post here over the next few months. Stay tuned.

Today's tip: Reduce noise for cleaner and also softer images.

As the ISO increases, so does the amount of noise in a digital image – especially at high ISO settings, and extra especially in low light situations. Long exposures also add to noise in a digital file.

Also, low-end digital SLRs have more noise at high ISO settings than high-end digital SLRs. In addition, compact digital cameras have more noise than digital SLRs when set to the same ISO – due to the smaller size of the sensor.

Reducing noise is easy. One method is to use the in-camera noise reduction feature, but that slows down the shooting rate. A more popular method is to use a noise reduction program or plug-in.

For this HDR image, taken before 6 AM in very low light in a Buddhist temple in Cambodia, I had my 5D Mark II set at ISO 1000. As good as the camera is at delivering low-noise images, the resulting file did have a bit of noise – due to the very low light and relatively long exposure (several seconds).

As an aside, this image looks very soft because there was no direct light – only very soft, diffused, low light. The light level was so low, in fact, that I had to use the LCD illumination button on my camera to check my settings. In this image, the mood and feeling is most important.

I first created this HDR image with Photomatix, and then enhanced it in Topaz Adjust. In Topaz Adjust, I used the Noise reducing feature in that plug-in. It worked quite well at cleaning up the image.

When you reduce noise, you also reduce the sharpness of an image. Check out the image below.
For this image, taken in Bodie State Historical Park in California, I reduced the noise (again using the Noise feature in Topaz Adjust) to the point where the detail in the image was lost – creating a painterly-type image. Try this effect. You may like it.

For info on Topaz Adjust, which also offer Topaz DeNoise, click here. You can save a bundle by ordering a bundle :-)

For info in Photomatix, click here.

Explore the light,

P.S. A note on noise: My dad used to say: If a picture is so boring that you notice the grain, it's a boring picture.


CGarison said...

As I was processing some HDR work this past weekend, I noticed that Topaz Adjust was creating a "blockish" looking noise effect in the images that was distorting the look I was trying to achieve. I mean, who wants square clouds?

In the end, I pulled the look I wanted by re-importing the image into Lightroom and removing the noise there. I like the softer image as it does look much more artistic when printed in large format, but there is still a part of me that yearns for sharpness.

Rick Sammon said...

CG - Where you working on a shiny screen laptop? I have seen the effect you mentioned there....