User Guide

User Guide Neat Image

20-Nov-03

12. Tips and Tricks

12.1. Preventing banding

In some cases, the banding effect may appear when applying the noise filter to images with faint

brightness gradients. This effect is quite rare for normal images, especially when viewed on a true color

display (it can be more visible on hi-color displays

To avoid banding, try to reduce the noise reduction amount for the high frequency component to 50%.

12.2. Filtration of shadow areas

In some situations, it is preferable to filter only the shadow areas of images leaving bright areas intact.

You can do this with Neat Image by using the noise profile equalizer to limit or stop filtration of bright

image areas.

The noise profile equalizer sliders correspond to particular ranges of brightness (individually for each

color channel) of the RGB color space. The position of each slider changes (fine-tunes) parameters of

the noise profile for the corresponding range of brightness. The lower a slider, the less filtration will

eventually be applied to image elements that belong to the corresponding range of brightness.

Therefore, to filter only shadows you can manually move all the 'bright' sliders down (refer to the

gradients on the bottom of noise profile equalizer). For example, move down all but the three ‘darkest’

sliders in each RGB channel.

Using this method, you can effectively prevent filtration of the bright image areas.

If you use the plug-in version of Neat Image, you can filter shadows/lights only using the selection

capabilities of your image editor. Select an area to be processed (for example, select shadows based on

low brightness values) and invoke Neat Image plug-in to filter this area.

12.3. Partial filtration

Some images contain both noisy and clean areas and it may be preferable to filter only noisy areas. This

can be manually done by combining two images – original and filtered one – in an image editor. For

example, the following steps can be followed if you use the standalone version of Neat Image:

1. Filter the input image in Neat Image (so that noisy areas are cleaned) and save the output image to

a new file;

2. Open this new file in an image editor;

3. Place the filtered image in a new layer on top of the original image;

4. Adjust the transparency of the new layer so that noisy areas look fine;

5. Select and delete the areas of the new layer where filtration is not necessary or excessive (you may

want to use the eraser tool with adjustable transparency and shape).

12.4. Faster processing

You can get better filtration speed if one (or more) of the image components is not processed. To disable

processing of a frequency component set the noise reduction amount and sharpening amount to 0% for this

component. To disable processing of a color channel component set the noise reduction amount to 0% and

disable sharpening of this channel.

The filtration speed is 15-25% higher per image component left out of the filtration process.

This is a common problem of hi-color displays. If the display does not have enough colors then the image can have

some bands of the same colors. Dithering is usually used to mask this problem on such displays. An original image

usually contains some noise, which acts like dithering. When Neat Image removes this noise, the underlying problem

of banding may come up again. A solution is to use a true color display or a better image viewer (in hi-color), which

applies some dithering automatically.