SpeedSix.LensFlare (Discreet Lenz Raptor)

PURPOSE

Lens flares and lens spots before the eyes. This effect simulates some of the effects seen when a very bright light source is in or near the field of view of a camera. These effects are caused by some of the incoming light not being directed to a point on the image but rather being reflected around the internal optical and mechanical components of the camera system. This light finally contributes to the image in the form of "beams" radiating out from the light source, rings and disks caused by geometrical elements of the camera (some circular, some polygonal - e.g. the iris diaphragm) and an unfocussed "glow" which partially washes out the image dependent on distance from the light source location (and quite possibly over the whole of the image). The "un-imaged light" that causes these effects is frequently dispersed in wavelength to create many unexpected colours across the spectrum.

INPUT CLIPS

1: Input Clip : A clip over which lens flares are to appear.
2: Light : A clip that can optionally modulate the light source colour. As the light source position moves over this clip, the colour under the light source can be multiplied by the light source colour. If the the Light Clip Fraction control is set to 1.0 all the light source colour will come from this clip. Otherwise it will be a blend of the light source colour and the light clip colour.
3: Obscure : A clip that can optionally modulate the light source brightness. As the light source position moves over this clip, the fraction of the light source area covered by white in this clip is evaluated and used to control the light brightness. If the whole of the light source area is covered by white areas of this clip, the brightness is zero. If none of the light source area is so covered, the brightness is as set by the light brightness control. Clip values other than white will be partially transparent as evaluated by their luminance.
4: Track : A clip that can optionally be used as the input to the (optional) light position tracking function. The light position tracker is a simple tracker which may benefit from having a simple input clip - e.g. a blob indicating where the light source is. If this clip is not used, the Input Clip is used as the light position tracker input. Please see the Tracking Notes section below for additional guidance.

Pre-built flare. Sets all controls to get a particular sort of flare look. The presets are all designed using a black background. If you use them over another colour try using the Light Brightness and Contrast controls on page one to balance the result to suit. See the Built-in Preset Effects section to see pictures showing what these look like.

LightPos (Position Default: 0.27,0.64)
Light source position.

LightBright (Number Min: 0.00, Max: 5.00, Default: 0.50)
Brightness of the light source. This may be modified by the area of the light source (determined from its radius set by the LightRad control) that is obscured by solid objects in the Obscure Clip.

LightCol (Colour Box Default: R: 65535, G: 65535, B: 65535, A: 65535)
Colour of the light. This may be changed by a LightClip if desired (you will also need to set LightClipFrac to something more than 0.0).

LightClipFrac (Number Min: 0.0, Max: 1.0, Default: 0.0)
Fraction of the light colour contributed by the light clip.

Contrast (Number Min: 0.01, Max: 10.0, Default: 1.0)
Contrast of the flare components

Warm (List Box Options: Blast | Burst | Smoothy | Dawn | Golden | RedDwarf | Hot | RainbowStar | Pretty, Default: Blast)

Pre-built flare. Sets all controls to get a particular sort of flare look. The presets are all designed using a black background. If you use them over another colour try using the Light Brightness and Contrast controls on page one to balance the result to suit. See the Built-in Preset Effects section to see pictures showing what these look like.

Use Obscure (Checkbox Default: Off)
Use the Obscure Clip to control the light brightness. The fraction of the light source area (determined via the light source radius LightRad) obscured by the Obscure Clip is determined and used to scale the light brightness. The Obscure Clip is treated as a matte, with full white being fully obscuring and black being transparent. If Directional Obscure is turned on, the Obscure Clip is used in a slightly different way. In that case, the light brightness depends on the angle around the light. The brightness is inversely proportional to how much white in the Obscure Clip lies along the angle within the light radius. This directional brightness variation affects only the Flare beams. No other element is affected.

DirObscure (Checkbox Default: Off)
Use the Obscure Clip to control the light brightness as a function of angle around the light. This directional brightness will only affect the flare beam elements and only if ObscureOn is selected.

LightRad (Number Min: 0.001, Max: 1.000, Default: 0.1)
Radius of light source itself. Used to determine obscuration in conjunction with the Obscure Clip. It has no effect if the Obscure Clip is not being used.

Dither (Number Min: 0.00, Max: 100.00, Default: 0.0)
Add a dither to break up any visible mach banding.

FBackFill (Checkbox Default: On)
Softens the zone of the flares.

GBackFill (Checkbox Default: Off)
Softens the zone of the flares.

More (List Box Options: Halogen | Sharp | Graphic | SmallWhite | SearchLight | CamCorder | 105Prime | Hi8 | SpotLight, Default: Halogen)

Pre-built flare. Sets all controls to get a particular sort of flare look. The presets are all designed using a black background. If you use them over another colour try using the Light Brightness and Contrast controls on page one to balance the result to suit. See the Built-in Preset Effects section to see pictures showing what these look like.

Tracking (Checkbox Default: Off)
Turn on to use the built-in tracking facility.

Track Light (Checkbox Default: Off)
Use the built-in tracking facility to attempt to track the light source position. The tracker will use the Input Clip for its calculations by default. You can choose to use the Track Clip instead by turning on the Use Track Clip checkbox. The tracking template is always centered on the current light source position when a tracking template "snapshot" is taken. This happens when you press the Set Track Template button and also whenever tracking is turned on, or the template radius is changed or the input image resolution changes. Please see the Tracking Notes section below for additional guidance.

UseTrackClip (Checkbox Default: Off)
If selected, use the Track Clip as input to the light source position tracker, instead of the Input Clip. Please see the Tracking Notes section below for additional guidance.

TrackTemplateR (Number Min: 0.001, Max: 0.100, Default: 0.01)
Size of the tracking template region. This is the length of the sides of a "square" area. This area is used to take a tracking template "snapshot" from either the Input Clip or the Tracking Clip. The conditions under which a "snapshot" is taken are explained in the description of the TrackLightPos control. The "snapshot" is always taken at the current light position.

TrackSearchS (Number Min: 0.001, Max: 0.200, Default: 0.05)
Size of the tracking search region. This is the length of the sides of a "square" area inside which the tracker will look for the best match with the tracking template "snapshot" (either in the Input Clip or the Tracking Clip according to the selected tracking image source). The position of the best match inside this region is estimated with sub-pixel resolution and used to update the current light source position when tracking is turned on. Please see the Tracking Notes section below for additional guidance.

SetTrackTemplate (Pushbutton)
Set the light source position tracker template. A "snapshot" is taken of the Input Clip or the Track Clip (according to the UseTrackClip control), centered on the current light position. This "snapshot" is then used to search for any movement of the light source in subsequent frames. Changing the template size, the clip to try to track, turning tracking off and then on again, or changing the resolution of the images being processed will also result in a new template "snapshot" being automatically taken. Please see the Tracking Notes section below for additional guidance.

TurnOffAll (Checkbox Default: Off)
Turn off any active flares, glows, rings and secondaries to speed up the tracking. Once the track has been set up turn off to re-activate your flares etc. All the controls relating to the effects will disappear so you MUST turn this control off again to get them back!

Flare CONTROL PAGE

Flare (Checkbox Default: On)
Turn on the primary flare element. The primary flare element has many beams radiating from the light source position. These beams fade off with distance from the light source. They have a colour (usually white) which is multiplied by the light source colour. That colour can optionally be blended with a rainbow (or spectrum). The rainbow colours pass through red to violet with distance from the light source. The initial colour and the number of times we pass through the rainbow over the maximum beam length can be controlled.

Beams (Number Min: 1, Max: 1000, Default: 30)
Number of beams radiating from the light source center. The flare is made up of one or more such beams. These beams are created at random angles around a circle. This angular distribution is set by FlareSeed random number seed control.
If the FlareSeed is set to the special value of 0, then the distribution of beams is not random. In that case, the beams are uniformly distributed around the circle. E.g. with six beams would each would have 60 degrees between them.

FlareColour (Colour Box Default: R: 16176, G: 14128, B: 65535, A: 65535)
Base colour of the beams. Spectral colour may be added on top of this - i.e. a colour selected from a rainbow, the colour selected being dependent on distance from the light source position. The amount of spectral colour added in is controlled by the SpectralFrac control. The final colour of a beam at any point is the combination of the base and spectral colour multiplied by the light source colour.

Bright (Number Min: 0.00, Max: 5.00, Default: 0.4)
Varies the relative brightness of the flare element. The beam brightness is the light source brightness multiplied by this flare brightness.

Rotation (Number Min: 0.0, Max: 360.0, Default: 0.0)
Rotation of the beams about the light source center.

FlareDistort (Number Min: 1.00, Max: 5.00, Default: 1.00)
Radial distortion for the flare element. This can be used the make the flare beams lie within a vertically squashed circle (an ellipse!). At 1.0, the flare beams will be un-distorted (lie within a circle).

Scale (Number Min: 0.01, Max: 5.00, Default: 1.00)
Overall size scaling factor for the flare element. All the beams are scaled up and down by this factor (about the light source position).

MinRadius (Number Min: 0.002, Max: 5.000, Default: 0.41)
Minimum beam radius. Beams will be created that are at least this long (measured from the light source center). If FlareSeed is 0, the beams will all be this long.

MinWidth (Number Min: 0.002, Max: 0.500, Default: 0.010)
Minimum beam width. This is the narrowest beam that will be created. If FlareSeed is 0, the beams will all be this wide.

StartWidth (Number Min: 0.10, Max: 5.00, Default: 0.4)
Beam starting point width scale. The beams width at the light source position is the width the beam was created at, multiplied by this scale factor. The width of the beam can change over its length from this width to the end width - the product of the beams creation width and the end point width scale.

SpecialBright (Number Min: 1.0, Max: 20.0, Default: 2.0)
Any special dominant beams in the flare (you can choose no dominant beam, vertical dominant, horizontal dominant or both vertical and horizontal) will be this much brighter than any other beam in the flare.

SpecialLength (Number Min: 1.0, Max: 10.0, Default: 2.0)
Any special dominant beams in the flare (you can choose no dominant beam, vertical dominant, horizontal dominant or both vertical and horizontal) will be this much longer than any other beam in the flare.

SpecialWidth (Number Min: 1.0, Max: 10.0, Default: 2.0)
Any special dominant beams in the flare (you can choose no dominant beam, vertical dominant, horizontal dominant or both vertical and horizontal) will be this much wider than any other beam in the flare.

FlareHarmonics (Number Min: 0, Max: 3, Default: 0)
If the Flare beam distribution is not random, insert this many extra sets of beams between the Nbeams main beams. The first extra set will be half the length of the main beams; the second one quarter the length and the third one-eighth.

MaxRadius (Number Min: 0.002, Max: 5.000, Default: 0.94)
Maximum beam radius. This is the longest beam length that will be created.

MaxWidth (Number Min: 0.002, Max: 0.500, Default: 0.050)
Maximum beam width. This is the widest beam that will be created.

EndWidth (Number Min: 0.10, Max: 5.00, Default: 0.50)
Beam end point width scale. The beams width at its end is the width the beam was created at multiplied by this scale factor. The width of the beam can change over its length from the starting width to this end width.

SpectralFrac (Number Min: 0.00, Max: 1.00, Default: 0.00)
Contribution of a colour from a rainbow (or spectrum) to the flare colour. This colour changes with distance from the light source center at a rate controlled by SpectralCycles. When added to the flare base colour, it determines the flare colour, which is then multiplied by the light source colour to form the final colour. At 0.0 there is no contribution from a rainbow and the flare colour is the base flare colour.

SpectralCycles (Number Min: 0.10, Max: 10.00, Default: 1.00)
Number of cycles of a spectrum that will take place over the MaxRadius length from the light source center. The higher this number, the more quickly the rainbow colour will change with distance out from the light source.

SpectralPhase (Number Min: 0.00, Max: 1.00, Default: 0.00)
Starting point (i.e. colour) for the spectrum at the light source position.

FlareSeed (Number Min: 0, Max: 7483648, Default: 12345)
Random number seed that determines the angular distribution of the beams. Changing this number will create a new set of beams with a different angular distribution.
The value 0 is special - it indiactes that there is to be no randomness in the beam distribution. If there are 6 beams, they will be positioned equally spaced around a circle at intervals of 60 degrees.

BeamDom (List Box Options: None | Horizontal | Vertical | Both, Default: Horizontal)

Dominant beam direction. This can guarantee that a horizontal or vertical beam (or both) is created regardless of the rest of the angular beam distribution. This beam with be as long and wide as is allowed and will be drawn at maximum brightness.

SymmetricBeams (Checkbox Default: On)
Make all beams symmetrical about the light source center. If off, beams start from the light source position. If on, beams have their middle at the light source position.

Glow Ring CONTROL PAGE

GlowBall (Checkbox Default: Off)
Turn on the primary "glow ball" element. This is a ball shaped glow centered on the light source. You can control its radius and how quickly it fades away. The colour (usually white) can be set, and this is multiplied by the light source colour to find the "glow ball" colour. This colour can be blended with a rainbow (or spectrum) the colour of which varies with distance from the light source, as described for the primary flare element.

GlowRadius (Number Min: 0.000, Max: 5.000, Default: 0.150)
Radius of the glow ball (center is the light source position).

GlowFadeOff (Number Min: 0.000, Max: 5.000, Default: 0.200)
Length (from the light source center) over which the glow ball fades to zero intensity.

GlowBright (Number Min: 0.00, Max: 5.00, Default: 1.0)
Varies the relative brightness of the glow element. The glow brightness is the light source brightness multiplied by this glow brightness.

GlowColour (Colour Box Default: R: 16176, G: 14128, B: 65535, A: 65535)
Colour of the glow. This colour is multiplied by the light source colour to find the final glow colour.

GlowProfile (List Box Options: Linear | Hermite | Cosine | Tight | Halo, Default: Cosine)

Mathematical function used to control how the glow fades across its FadeOff width. The glow intensity falls off to zero over its FadeOff width with a "shape" controlled by this setting.

GlowDistort (Number Min: 1.00, Max: 5.00, Default: 1.00)
Radial distortion for the glowball element. This can be used the make the glow lie within a vertically squashed circle (an ellipse!). At 1.0, the flare beams will be un-distorted (lie within a circle).

Ring (Checkbox Default: Off)
This element is a single ring surrounding the light source position. You can control its radius and how thick it is. You can also control whether it starts abruptly and dies away over its width, builds up over its width and stops abruptly, or is symmetrical in the way it builds up and fades away. You can give the ring its own colour (often white), which is multiplied by the light source colour and optionally blended with a rainbow as described above for the "beam" and "glow ball" elements. The colour selected from the rainbow at any point depends on position within the width of the ring.

RingRadius (Number Min: 0.000, Max: 5.000, Default: 0.500)
Radius of the ring (center is the light source position).

RingFadeOff (Number Min: 0.000, Max: 5.000, Default: 0.80)
Length (measured from the ring radius, inside, outside or on both sides of the ring radius, depending on ring type) over which the ring fades to zero intensity.

RingBright (Number Min: 0.00, Max: 5.00, Default: 1.0)
Varies the relative brightness of the ring element. The ring brightness is the light source brightness multiplied by this ring brightness.

RingColour (Colour Box Default: R: 65535, G: 65535, B: 65535, A: 65535)
Colour of the ring. This colour is multiplied by the light source colour to find the final ring colour.

RingDistort (Number Min: 0.10, Max: 5.00, Default: 2.00)
Radial distortion for the ring element. This can be used the make the ring a prolate or oblate ellipse for values less than 1.0 and greater than 1.0. At 1.0, the ring will be circular. This can also be used with polygonal settings - in which case the results are "interesting"!

Rotation (Number Min: 0.0, Max: 360.0, Default: 0.0)
Rotation of the ring about its center.

RingType (List Box Options: OutRing | InRing | SymRing, Default: SymRing)

Shape of the ring element. An OutRing starts abruptly RingRadius distance from the light source center and its intensity falls to zero after RingFadeOff distance beyond RingRadius. An InRing starts RingFadeOff distance inside the RingRadius and end abruptly at RingRadius. A SymRing builds up to maximum intensity at RingRadius, beginning from zero at RingFadeOff distance inside the RingRadius and returning to zero at RingFadeOff distance outside RingRadius.

RingSides (Number Min: 0, Max: 50, Default: 0)
Number of straight sides for the ring element. Any number less than 3 will give a circle. Three will give a triangle, 4 a square, and so on. Commonly seen polygonal shapes in real camera lens flares are pentagons and hexagons (although I've sometimes seen triangles on camcorders).

RingSpectralFrac (Number Min: 0.00, Max: 1.00, Default: 1.00)
Contribution of a colour from a rainbow (or spectrum) to the ring colour. This colour changes with distance from the light source center at a rate controlled by SpectralCycles. When added to the ring base colour, it determines the ring colour, which is then multiplied by the light source colour to form the final colour. At 0.0 there is no contribution from a rainbow and the ring colour is the base ring colour.

RingSpectralCycles (Number Min: 0.10, Max: 10.00, Default: 1.00)
Number of cycles of a spectrum that will take place over the FadeOff. The higher this number, the more quickly the rainbow colour will change with distance out across the FadeOff region.

RingSpectralPhase (Number Min: 0.00, Max: 1.00, Default: 0.88)
Colour the spectrum will have at the RingRadius.

RingProfile (List Box Options: Linear | Hermite | Cosine, Default: Hermite)

Mathematical function used to control how the ring fades across its FadeOff width. The ring has maximum intensity at its RingRadius and falls off to zero over its FadeOff width with a "shape" controlled by this setting.

RingPos (Number Min: 0.00, Max: 1.00, Default: 0.00)
Set the position of the Ring element along the Secondary elements line. Typically, the Ring will be wanted centered on the light source, but this lets you move it if desired.

FringeSeed (Number Min: 1, Max: 7483648, Default: 12345)
Random number seed that determines the appearence of any ring fringeing. Changing this number will create a new set of fringes with a different angular distribution.

FringeFreq (Number Min: 1.00, Max: 10.00, Default: 1.00)
Controls the maximum detail in the ring fringeing effect.

FringeAmp (Number Min: 0.00, Max: 1.00, Default: 1.00)
Controls how deeply the ring intensity is modulated by the fringeing effect.

Secondaries CONTROL PAGE

Secondaries (Checkbox Default: Off)
Secondary elements are "spots" or "rings" strung out along a "secondary element line". This line satrts at the light source position and passes through the center of the image. The number of elements can be controlled. The position of the elements along the line is random and is determined by setting a random number seed specific to secondary elements. The colour of the elements is a controllable blend of the light colour, a base colour for all secondary elements, and a random colour variation, the hue range of which can be controlled.

Spots (Number Min: 0, Max: 300, Default: 30)
Number of secondary elements (spots and rings). This number of elements will be created with their parameters randomly varied between limits set by the secondary element controls (on this page). The distribution of parameters is controlled by the SpotSeed random number seed.

SpotSides (Number Min: 0, Max: 50, Default: 0)
Number of straight sides for the spots and rings. All the secondary elements will have the same number of sides.

Bright (Number Min: 0.00, Max: 5.00, Default: 1.00)
Varies the relative brightness of the spot elements. The spot brightness is the light source brightness multiplied by this spot brightness.

Scale (Number Min: 0.01, Max: 5.00, Default: 1.00)
Overall size scaling factor for the spot elements. All the spots are scaled up and down by this factor (about their center positions).

Rotation (Number Min: 0.0, Max: 360.0, Default: 0.0)
Rotation of the spots about their centers.

SpotDistort (Number Min: 0.10, Max: 5.00, Default: 1.00)
Radial distortion for the spot elements. This can be used the make the spots prolate or oblate ellipses for values less than 1.0 and greater than 1.0. At 1.0, the spots will be circular. This can also be used with polygonal settings - in which case the results are "interesting"!

SpotMinRadius (Number Min: 0.001, Max: 5.000, Default: 0.0020)
Minimum spot radius. Spots will be created that have at least this radius.

SpotMinFade (Number Min: 0.0001, Max: 5.000, Default: 0.005)
Minimum spot fadeoff distance. Spots will be created that have at least this fadeoff distance.

SpotHueVar (Number Min: 0.00, Max: 1.00, Default: 0.50)
This controls how much variation there will be in spot colour about the chosen spot base colour. The colour of a spot is the spot base colour, randomly shifted along the spectrum by up to this much of the full spectrum length, multiplied by the light source colour.

SpotColour (Colour Box Default: R: 16176, G: 14128, B: 65535, A: 65535)
Colour of the spots. This colour is first perturbed to an extent controlled by the Spot Hue Variance, then multiplied by the light source colour to find the final spot colour.

LineLength (Number Min: 0.000, Max: 10.000, Default: 2.000)
Length of the line along which "secondary elements" will appear. Secondary elements are "spots" or "rings" strung out along this line. The number of elements can be controlled. The position of the elements along the line is random and is determined by setting a random number seed specific to secondary elements. The colour of the elements is a controllable blend of the light colour, a base colour for all secondary elements, and a random colour variation.

SpotSeed (Number Min: 1, Max: 7483648, Default: 12345)
Random number seed that determines the distribution of the spots along the secondary element line (which starts at the light source and passes through the center of the image. Changing this number will create a new set of spots with a different distribution along that line.

SpotsBothSides (Checkbox Default: Off)
Make spots appear along the continutaion of the secondary element line through the light source on the side away from the image center. This seems to be seen only rarely in real camera flares - but it does happen sometimes. Please note that turning this on will change the positions of spots (relative to when it was off).

SpotMaxRadius (Number Min: 0.001, Max: 5.000, Default: 0.050)
Maximum spot radius. This is the biggest radius spot that will be created.

SpotMaxFade (Number Min: 0.0001, Max: 5.000, Default: 0.010)
Maximum spot fadeoff distance. This is the biggest fadeoff spot that will be created.

SpotBrightVar (Number Min: 0.00, Max: 1.00, Default: 0.50)
This controls how much variation there will be in spot brightness from full brightness. If this is 0.0, all spots will be maximally bright. If this is 1.0, spot brightness will vary from maximally bright to zero brightness (invisible).

SpotDiskProb (Number Min: 0.00, Max: 1.00, Default: 1.00)
This controls the relative likelyhood of creating a Disk (filled circular or polygonal) secondary element, as opposed to a ring of some kind. The probabilities specified for each type of disk or ring are summed, and the chance of choosing a Disk when the secondary elements are created is the SpotDiskProb divided by that sum. The actual size of this number therefore isn't important. What matters how big or small it is compared to the other element probability specifications (SpotOutRingProb, SpotInRingProb and SpotSymRingProb).

SpotOutRingProb (Number Min: 0.00, Max: 1.00, Default: 0.00)
This controls the relative likelyhood of creating an OutRing secondary element, as opposed to a disk or some other kind of ring. The probabilities specified for each type of disk or ring are summed, and the chance of choosing an OutRing when the secondary elements are created is the SpotOutRingProb divided by that sum. The actual size of this number therefore isn't important. What matters how big or small it is compared to the other element probability specifications (SpotDiskProb, SpotInRingProb and SpotSymRingProb).

SpotInRingProb (Number Min: 0.00, Max: 1.00, Default: 0.00)
This controls the relative likelyhood of creating an InRing secondary element, as opposed to a disk or some other kind of ring. The probabilities specified for each type of disk or ring are summed, and the chance of choosing an InRing when the secondary elements are created is the SpotInRingProb divided by that sum. The actual size of this number therefore isn't important. What matters how big or small it is compared to the other element probability specifications (SpotDiskProb, SpotOutRingProb and SpotSymRingProb).

SpotSymRingProb (Number Min: 0.00, Max: 1.00, Default: 1.00)
This controls the relative likelyhood of creating an SymRing secondary element, as opposed to a disk or some other kind of ring. The probabilities specified for each type of disk or ring are summed, and the chance of choosing an SymRing when the secondary elements are created is the SpotSymRingProb divided by that sum. The actual size of this number therefore isn't important. What matters how big or small it is compared to the other element probability specifications (SpotDiskProb, SpotOutRingProb and SpotInRingProb).

Tracking Notes

Tracking can be used to have the light source position (LightPos) follow some feature in your input clip. Sometimes, you may want to follow something in another clip (track clip) for reasons discussed below.

Setting up to track something in your input clip or in an auxiliary tracking clip is easy if a few simple principles are followed.

When should you use a tracking clip?
The tracker built in to LensFlare is fairly simple (although it is sub-pixel accurate) and if there isn't a feature at the desired light source position in the input clip that looks easy to track, you may want to generate an auxiliary tracking clip from the input clip that may be more "trackable".

For reliable tracking, you generally want something with decent contrast and something that looks more or less like a corner or a cross. However, repetitive patterns (e.g. chicken wire fences) might give problems. The tracker works in monochrome, so contrast needs to be assessed with that in mind.

Apart from increasing contrast, another application for an auxiliary tracking clip is to add an offset. The built-in tracker does not have an "offset tracking" capability. If there is a suitable object for tracking that follows the desired light source position, but is not at that position, you could take the input clip and shift it with some host platform function so that the trackable feature is positioned where you want the light source, using the shifted input clip as the track clip.

Recommended steps to set up and use the tracker

Here is a recommended procedure.

Turn off Track Light if it is on.
Turn off all the lens flare effects - Flare, GlowBall, Ring, Secondaries.
Position the LightPos so the center as shown on the overlay is over the feature you want to track.As explained above, this must also be the light source position, as the tracker has no offset facility. One way of simulating an offset facility is to shift the input clip so a trackable feature lies at the light source position, and use that shifted clip as the Track Clip. If you do this, turn on the UseTrackClip control.
Turn on Track Light. This records what is under the light location as a tracking template which the tracker will subsequently attempt to find every time a frame is processed.
Adjust the TrackTemplateRadius using the purple box overlay to enclose the feature you intend to track. This will update the tracking template as you make adjustments.
Adjust the TrackSearchSide using the green box overlay to cover the region in which the feature being tracked will move from one frame to the next. This needs to be big enough to accomodate the motion of the feature, but ideally not much bigger - the bigger it is, the slower the tracker will run.
Allow animation or key framing on the LightPos control using the host system method of doing this.
Play through the clip. Hopefully, the tracker will follow the feature of interest, creating an animation path for the LightPos control.
Turn off Track Light.
Return to the first frame of the clip.
Turn on your desired lens flare effects.
Play through or render the clip. The LightPos will follow the animation path generated during tracking.

If the tracker loses track at some frame, stop the play through. Then:

Turn off Track Light.
Move to the frame where the track was lost.
Move the light position manually to the correct location.
Turn on Track Light
Modify TrackTemplateRadius and TrackSearchSide to values you think appropriate.
Start to play through again.

Built-in Preset Effects

To help you get started, many built in presets are supplied in LensFlare. You can choose one of these from any of the three list controls: Cool, Warm and More Presets. You can then adjust the controls from the starting point given by the preset to get the result you want.
Here are pictures of each of the presets:

Cool