Understanding the Focus Stacking Parameters

array(4) {
  ["_edit_last"]=>
  array(1) {
    [0]=>
    string(1) "3"
  }
  ["_edit_lock"]=>
  array(1) {
    [0]=>
    string(12) "1406638422:4"
  }
  ["cptr_related"]=>
  array(1) {
    [0]=>
    string(6) "a:0:{}"
  }
  ["dropdown_menu"]=>
  array(1) {
    [0]=>
    string(1) "5"
  }
}

For Helicon Focus, we tried to include as few parameters as possible. In most cases, you can just use the default values and get good results. But for complex situations, you may need to fine tune the parameters.

Calculation Methods

You can choose between three algorithms for focus stacking: methods A, B, and C. Which method will work the best depends on the image, the number of images in the stack, and whether the images were shot in random or consecutive order. While we have some recommendations regarding which method to choose, there is no strict rule as to which method will work better in any particular case. So we suggest you try all three of them.

	Method A	Method B	Method C
The image has a simple surface with no sudden changes in surface level.
The image has many crossing lines and changes in surface level.
There is glare in the image.
The stack is large (> 100 images).
The images were NOT shot in consecutive order (i.e., they were not shot from front to back or vice versa).
Preserving colors and contrast is a priority.

Here's a brief explaination of each method:

• Method A computes the weight for each pixel based on its contrast, after which all the pixels from all the source images are averaged according to their weights.
• Method B finds the source image where the sharpest pixel is located and creates a "depth map" from this information. This method requires that the images be shot in consecutive order from front to back or vice versa.
• Method C uses a pyramid approach to image representation. It gives good results in complex cases (intersecting objects, edges, deep stacks) but increases contrast and glare.

The Radius Parameter

Radius is the most important parameter for processing. We mostly advise you to try different values. Start from the default value and then set it to its minimum and see what happens. Next try to increase the value to get rid of any noise or artifacts, particularly halos along the edges.

If your image has fine details and thin lines, as most images do, a low radius level (3-5) will probably yield the best results, although you will probably get more noise and a halo effect. So you'll need to try to find a balance.

Method B, Radius = 1	Method B, Radius = 22

Increasing radius can help get rid of or minimize halo. In general, if you have a halo effect, try increasing the radius until doing so helps to minimize halo. At that point, stop increasing the radius, so as to preserve as much detail as possible.

Method B, Radius = 2	Method B, Radius = 22

All images are different and there is no strict rule about which radius will work better.

Here's an explanation of how the algorithms use the radius parameter. The radius parameter defines the number of pixels around each pixel that are used to calculate its contrast. The focus-stacking algorithms take each pixel and calculate whether or not it's sharp, after which the software combines the sharp pixels, assuming that the greater contrast a pixel has, the sharper it is.

The Smoothing Parameter

All focus-stacking algorithms find and combine the sharp areas. Smoothing defines how the sharp areas are combined. Low smoothing produces a sharper image, but the transition areas may have some artifacts. High smoothing will result in a slightly blurry image without any visible transition areas.

Start with the default smoothing. Then if you want more detail, decrease the smoothing value; if you get too much noise and too many artifacts, set a higher value.

Alignment Parameters

If your camera (or subject) moves between shots, you may need to increase the values for the alignment parameters. These define how much the program is "allowed" to adjust vertical and horizontal positioning, angle of rotation and magnification of images in the stack.

To change the alignment parameters, go to the Main Menu, open the "Preferences" dialogue (Main menu → Edit → Preferences...) and switch to the "Auto adjustments" tab.