<Return to the Table of Contents>

Resizing Controls


This section documents interface elements that control image size and quality. If you have questions about other, more general interface topics, please consult the User Interface Overview.

Most of the resizing controls in Blow Up behave like the Image Size dialog in Photoshop. If you are familiar with that then you can skip to the new controls: Duplicate Image, Sharpen Amount, and Add Grain.

When Blow Up starts, the Pixel Dimensions and Document Size sections are set to the current image size. The rest of the controls are set to the values from the last time you used Blow Up.

You can control the new size of the image through Pixel Dimensions or Document Size. Changing one will automatically update the other.

Pixel Dimensions

Pixel Dimensions are usually used for images destined for the Web or digital display. The top border of the Pixel Dimensions section displays the amount of memory needed to hold the original and new image. If you notice that the new memory size is gigantic, then check your Resolution to make sure it is reasonable.

Document Size

For images destined for print, the most intuitive way to specify their size is in the Document Size section. This section uses real world units like inches and centimeters. Resolution is important for print quality. High quality printing typically requires 300 pixels/inch. Images viewed from a large distance may be okay with much lower resolution.

Constrain Proportions

Selecting Constrain Proportions ensures that your image is resized regularly, that changing height proportionally changes width and vice versa. You should leave this on in almost all cases.

Duplicate Image Before Resizing

If this checkbox is on then a copy of your image will be resized, leaving your original image untouched. Otherwise your image will be resized in place.

Sharpen Amount

Enlargement always softens edges to some extent. Increasing the Sharpen Amount slider restores much of the sharpness of strong edges. This is accomplished by compressing the distance over which an edge transition occurs. The result is very different from traditional unsharp masking. Unsharp masking often creates distracting halos and sparkles. The sharpening of Blow Up does not have these problems and, as a result, is more subtle. It can, however, make your image overly smooth. So use only as much as is necessary.

In this image, sharpen values of 100, 35, and 0 were applied. Notice that the spots and edges of the butterfly wings appear more clearly defined in the upper panels where sharpening took place.

The sharpening of Blow Up is only designed to counteract softening caused by enlargement. If your original image is blurry, the plug-in will not be able to fix that. In that case you should use other sharpening techniques, such as unsharp masking, before enlarging with Blow Up.

Add Grain

Extreme enlargement and sharpening can result in an overly smooth image that looks like plastic. Adding some artificial film grain can provide a surprisingly realistic illusion of detail. Usually you only need to consider adding grain when your image is being enlarged over 200%. As with any effect, you should make it so subtle that most viewers will not know you did anything. Start by increasing Add Grain until you can see the grain. Then back the effect off until you can barely tell the grain is there.

This image looks a bit plastic when enlarged ten times original size. To give the illusion of detail, grain was added to the lower panel.

The film grain used in Blow Up is a simplified version of the film grain in our Exposure product. The grain is monochromatic (only affecting luminance, not hue or saturation). Grain size grows as the enlargement factor grows. If you enlarge 500% or more, then you can see the lumpy fractal nature of the grains. If you need more control over the look of the grain, turn off grain in Blow Up and apply it using Exposure.


<Return to the Table of Contents>