6. Resampling
– This control allows you to enlarge the images by interpolation to achieve
sub-pixel quality alignment. This will however reduce processing speed greatly. In the
processing page the images can be down sampled to their original size.
The resampling options are:
Bell – simple smoothing filter
B-Spline – no sharp transitions, but it can cause blurring
Lanczos – can cause "ringing" effect
Mitchell – no sharp transitions, often a good compromise between
"ringing" and "blurring"
During stacking and alignment every image is enlarged by the resample-factor.
7. Tracking Options
– When this option is set, the program will try to track the object
when it moves around. Steadily moving objects can be easily followed, unless they move
too fast. The largest movement between images the program is able to adjust directly
problems is about half the size (in pixels) of the alignment-box. When you enable the
predict option, the program will be able to trace faster moving objects as long as they
move in a constant direction. When the object moves in a more random fashion do NOT
use the predict option, instead increase the FFT-size to keep the feature easier in view. If
the misalign warning is set you will be notified when the program thinks it looses track of
the alignment feature, then you will be asked to realign the image.
If the object you want to register moves over the image-space like you can see in the above
example you will need to set the “track object” option. Track object will try to keep track of
the object by using the information of the previous shift. If the object slightly moved to the left
we expect it to be at least shifted to this position in the next frame also. If the object moves
in a steady fashion this feature will keep track of the necessary alignment. But for steady
moving or fast moving objects the “predict” track might also be helpful, With this feature the
program makes an expectation of the objects position based on the last shifts. If the object
moves fast or in a random way over the image the user is advised to use a larger FFT box.
8. Auto-optimization
– This setting is associated with three controls in the optimizing
options panel (#15). During optimization the pixel-by-pixel difference between the
image and the reference image is measured and minimized. Setting the "Optimize until"
thumbwheel (%) will make the optimization run until the difference between successive
runs is less than this value.
19
