76 Reply by Chas Tennis

(20 replies, posted in General)

Fluorescent Orange Ping Pong Ball Marker Test

A ping pong ball painted fluorescent orange (Tulip Slick Fabric Paint) was attached to the top of a tennis racket using a long, thin machine screw.  Fluorescent paint was chosen on the possibility that some paints might produce brighter markers in select wavelength bands.  An internet search did not yield information on the magnitude of the reflection plus fluorescent emission of these paints. Are any fluorescent paints considerably brighter than white in select wavelength bands?

http://www5.snapfish.com/snapfish/slide … =snapfish/

http://www5.snapfish.com/snapfish/slide … =snapfish/

One serve was recorded from the side against a darker background of trees in shadow. A second serve was recorded with a high camera (~10ft or 3 meters) so that the serve was seen from behind somewhat along the tennis ball’s trajectory. 

In order to see how well the tracker could follow the ping pong ball marker on the racket the Kinovea tracker was applied with no manual corrections.  In addition, in the view from behind the tennis ball was also tracked.  There was a consistent loss of track whenever any object approached a white line on the tennis court. 

These were first tests without optimizing, etc.   

Serve from the side with dark background, slightly underexposed. This setup is very useful for showing a considerable length of the racket path.
http://vimeo.com/25144725

Serve from high & behind.  Only the first serve has tracking.
http://vimeo.com/25414832

These videos cannot be viewed stop action, frame-by-frame on Vimeo.  The videos can be downloaded and viewed in Kinovea and probably other players such as Quicktime, etc.

Details on compression & non-compression as used by Vimeo are described in these FAQ-

http://vimeo.com/help/faq#compression

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77 Reply by Chas Tennis

(8 replies, posted in Bug reports)

joan wrote:

........ Feedback appreciated on wording, grammar, etc.

http://www.kinovea.org/screencaps/0.8.x/savedialog.png

Guidelines
- Forbidden/obscure words: metadata, stream, muxed.   
- option title: as simple as possible while retaining the meaning and not be ambiguous with other options.
- hint text: explain what will be saved and what will be the behavior of the exported file in other players as well as in Kinovea.

Your new wording covers nearly all of my uncertainty and issues.

I have no background in software other than as a user.  Generally I waste a lot of time interpreting some of the computer software terms. 

Unlike the term "drawings", the term "tools" is still causing me to do interpretations.   To me now the term "Tools" refers to some software, probably accessible by an icon, often in a toolbar, that produces something, label, comments, etc. for the video or the other accompanying metadata file(s).  Correct?  Better term would be for the output of the tools.  It is impractical to list all the tool outputs, labels, tracks, etc.   Is there another term or brief phrase more aimed at the end products of using the tools - "tool results", "tool overlays, etc.", "tool outputs" ?   

Do the terms "modifiable" and "editable" as being used here have the same meaning? If so I'd suggest picking one term.  My vote would be for "modifiable".

Suggest keeping the earlier term 'permanently' for the second option as in:

Save video with drawings and tools (or tool results) permanently applied to the images.

Is the term "images" distinct from just the term 'video'?  Suggest using 'video' unless there is a reason for "images".

One wording -

Save video with drawings and other tool results permanently applied for all video players.

Can the Tracker ever be used again after a Permanent Save? - To head off problems for new users. -  It seems that if the changes have been permanently saved with overlays written into the video that the tracker cannot be used properly again.   The tracker would see the overlays, labels, as any other object and often false track these overlays.  I guess that new labels, arrows, lines, angles, etc. could still be added and saved but the tracker use would probably be very limited after the first permanent save.  Does that seem correct?  If true, I'd like to see some warning that the tracker is limited after the first permanent save.

Suggest also putting the permanent save option at the bottom of the list as it seems like the final product while the other options imply ongoing analysis of the video.

As an option for less text maybe a Bullet format or Table format could be used for the important information. ? Columns: Kinovea & Other Video Players.  I have not put much thought into Tables or Bullets, just for consideration.

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78 Reply by Chas Tennis

(4 replies, posted in General)

I summarized some information on motion blur is a recent thread.   

Basic High Speed Video Camera Considerations & Cameras

The main thing for motion blur is the exposure time or shutter speed.   If the shutter speed cannot be manually controlled you probably have to live with whatever motion blur the camera AUTO exposure control produces under given conditions. 

I believe, but do not know, that some camera AUTO controls will adjust exposure by shortening the exposure time/shutter speed.  If you operate the camera in direct sunlight the exposure time/shutter speed may be much faster as adjusted by the camera's AUTO exposure electronics.   I don't know this but read that my Aiptek Action camera works in that way.  ? A characteristic of this would be minimum motion blur for videos in bright direct sunlight and increasing motion blur as light is reduced with a great deal of motion blur for indoor high speed videos. 

I am not familiar with the cameras that you mention. What is the shutter speed?  What settings can you adjust, lens aperture?, ISO?, etc. Do any have manual shutter speed control?   

If you must live with AUTO exposure control try shooting with each of your cameras in direct sunlight. If you can adjust aperture - use maximum aperture (lowest F/#), use highest ISO that you can set. See what the camera AUTO control can do for motion blur in direct sunlight.   Please let us know how you do if you experiment with your cameras.

I don't know your application but if it involves high speed video and you will have future use I would purchase a Casio camera with manual shutter speed control. Used models are F1, F20, F25. The FH 100 may no longer be manufactured (?) but some are still in stock.  I don't know of other high speed video cameras with manual control. I would like to hear of other cameras along with links that clearly state the shutter speed for high speed video operation.

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79 Reply by Chas Tennis

(20 replies, posted in General)

LED Marker Candidates & Throwies!

As far as cheap, self-contained LEDs are concerned it is hard to beat “Throwies”.  These connect directly (without circuitry) to button batteries that are supplied with the LEDs for under $1 each.  Light output for 2 weeks claimed.

“Throwies” - http://www.youtube.com/watch?v=YjTP_T-w … re=related

http://www.instructables.com/id/LED-Throwies/

Colors. LEDs are available in a variety of colors.  These LED emission spectra lend themselves to filtering as an option.
http://www.oksolar.com/led/led_color_chart.htm

For use as marker the best LEDs should probably be very bright.  They should also be ‘diffuse’ emitters – imperfectly diffuse as supplied but tending to emit more into all directions.  The light from ‘diffuse’ emitters is more likely to hit the camera lens than light from non-diffuse beam LEDs.   [Non-diffuse LEDs emit in a cone, for example, of only, say, 10°, severely limiting the use of that type of LED for markers.]

A good choice for marker candidates would be large, 10 mm, ‘super bright’, diffuse LED Throwies.  To try some I have spent some time trying to find this type for testing.   Finally I found some, just $7 for 10 10mm LEDs with batteries. But with minimum order and shipping the final cost exceeded $40, too much for me to test. 

http://www.lilyleds.com/Products/113/LED-Throwies

I did purchase 5, 5mm, non-diffuse, LEDs for under $10, shipped.  (The website is not now coming up.?). The output colors were white, red, blue, green, and amber.  Unfortunately, these were found to emit in a narrow beam of about 8° (hold a paper out in front of the LED to estimate).  While bright, strong sources when pointed at the camera, a slight tilt of the LED causes the beam to miss the camera lens and appear to have little brightness.  There may be some applications where the directional LEDs are better markers than the diffuse LEDS but the LEDs will have to stay pointed at the camera lens.

Video Test Non-Diffuse LEDs. A test of these LEDs, outdoors in overcast skies is shown with description of the test -  http://vimeo.com/25126884   The video can be downloaded.

I have not tested the tracking function of Kinovea for these directional LED sources in the video test.  One issue for tracking small light source markers is the Kinovea tracker's response to 'point' light sources. These LEDs, especially for low resolution high speed video cameras, will probably often just be imaged on just a few elemental detectors of the camera's sensor. 

I may still mount these non-diffuse LEDs in tissue paper diffusers but that will reduce output in some unknown way. 

I’m still looking for the large 10 mm, super bright, diffuse, LED Throwies, 10 for <$20 delivered,  to test next…….

Pending testing, I view LEDs as a good marker option for indoors and possibly workable outdoors in overcast skies. Guessing, LED markers are probably very difficult to use in direct sunlight.

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80 Reply by Chas Tennis

(8 replies, posted in Bug reports)

The important information seems to be:
1) What is saved.
2) What the saved video displays in both Kinovea and other players. Tracks, labels, grids,…etc.
3) Other information retrievable only by Kinovea.  Comments, velocities,……etc.

The screen where the options are presented has plenty of space to add some clarifying text even if incomplete.   

I have not put much thought into this wording and am not qualified to do so. The idea is to use more space to clarify & list what is saved and what can be viewed with K and other viewers. First, use a few words for each option. Second, shorten the information discussed in your reply.  Example -

A. Save unchanged video along with additional information used only by Kinovea.

Other Viewers - original video displayed.
Kinovea - comments, tracks, labels, grids....etc........will be saved (as Metadata) for viewing/use/retrieval? only in Kinovea.

B.  Save with permanent overlays to the video.

Kinovea & Other Viewers - tracks, labels, grids,....., etc., (as now viewed in K?) will be saved permanently and displayed in the video.
Kinovea - comments, ...,etc., will be saved within the same video file (as Metadata).

“Metadata” is defined on the internet so you could use it.  Give short footnote definition? Even I have an idea of what Metadata is now!

It seems to me that if the permanent option B. is used then the overlays are really in the video, overwriting the original video information. Then Kinovea could not be used to do additional tracking operations, etc.  Is that correct?  Option B would be the final save of work done in K for use outside in other viewers. ?

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81 Reply by Chas Tennis

(51 replies, posted in Cameras and hardware)

FH100 Settings. The FH100 can be set to save many settings including ISO.    MENU-REC-MEMORY (last) - ISO   In MEMORY pick what you want to have set when you turn on the camera next time.   Take care with this as, for example, you might not want the 10 sec trigger delay that you use for golf videos set the next time you grab the camera for stills.  I’m still reading the 202 page user's manual and finding good stuff for high speed video settings.

I have not used the high resolution continuous stills operation.  You can save 30 high resolution still frames taken as fast as 40fps.  I'm not sure of the fastest shutter speed and have not tested for the Jello Effect.

Update (2/23/2013) - Burst Mode & Jello Effect Stills Testing-  http://forums.dpreview.com/forums/post/39393614
For stills the Casio FH100 can also do 10 fps using a mechanical leaf shutter (slower than the 40 fps electronic shutter). There is less distortion because the camera uses a mechanical leaf shutter instead of a focal-plane mechanical shutter.

Some first thoughts on high speed imaging for archery:

Internet Search. Searched archery and FH100 or High Speed Video and found lots of Youtube examples.  YT applies video compression and you cannot do stop action frame-by-frame.  I use Vimeo for videos because Vimeo uploads the full video. You still cannot do stop action viewing on the Vimeo site.  But others can download the video for proper stop action frame-by-frame viewing__CORRECTION SEE BELOW

Details on compression & non-compression as used by Vimeo are described in these FAQ-

http://vimeo.com/help/faq#compression.

UPDATE (2/20/2017) -  Youtube Single Frame - use the " . " PERIOD keystroke and the " , " COMMA keystroke.

-------------------------------------------------------------
UPDATE 2/20/2017 - Vimeo has a stop-action single-frame capability viewing on line using the arrow keys.  When watching a Vimeo video on line you can do stop action single frame forward and backwards using the arrow keys.  Hold SHIFT KEY and use the RIGHT & LEFT arrows.

---------------------------------------------------------------------------

I had found another link, now misplaced, to an archery application in England that had very useful information for high speed videoing of archery (an archery club?).

Here’s an interesting discussion. 

http://paleoplanet69529.yuku.com/topic/ … foOcFstXng

General Framing. Frame to cover all the action and maybe a little more, +/- 5% on the sides, top & bottom.  If a video has anything interesting outside the frame that is missed and the event can be repeated, always repeat the event and video it again.  Erase the poorly framed video later.   

Along the Trajectory Viewpoint. Camera views along (parallel to) and on the line of the trajectory's line will show the arrow for some distance.  Use the longest FL lens setting, 240mm, and frame the archer tightly by moving back.  If you use a wide angle FL the arrow image will become too small as it moves away and you will lose it much sooner.  On the other hand, wide angle lens settings probably produce a more attractive video of the archer. 

Along the Trajectory Viewpoint for Incoming Arrows - Not for the Faint-of-Heart or Careless. You can also shoot just to the side of or even at expendable mirrors for videos of incoming arrows – perhaps for the first time.  But the camera has to be very well protected including from arrows ricocheting from the mirror. As a last protection the camera should view through a Lucite protective window (1/2”) and probably be in a heavy protective box.  The smaller the mirror the closer the camera must be…………..

Backgrounds. To see arrows pick your backgrounds carefully.  Woods in shadow are convenient backgrounds as I just found for tennis serves.  Black targets that contrast with the arrows, etc.

Daylight Illumination. For overcast I can shoot at 1/10,000s and ISO 3200 where 1/10,000s is very adequate for tennis strokes.  But in direct sunlight 1/40,000s should work also for larger apertures.  1/40,000s will catch the arrows with less motion blur as calculated earlier. 

LED Markers. I did some tests recently for markers using LEDs that are available very cheaply - “Throwies”.  The ones I tested had directional beams (light emitted into an 8°cone) and therefore I did not think they were suitable for markers for most athletic motions.  For your arrows they might be ideal.  You might attach one to your arrow pointing back and see what you get.  I don't think one of these coin-sized LED/Battery assemblies can be a safety problem but consider with due care.

Arrow velocity.  Velocity equals distance travel divided by the time between frames.  If known, use the arrow length in the video as a convenient scale.  Be aware of motion blur errors which can easily be made negligible.

Arrow Impacts. Use the frame rate and motion blur calculations in this thread along with arrow velocity to calculate whether you can expect interesting results.  Use 1,000fps and a very tight coverage of say, the popular apple target. Protect the camera from stray arrows and if necessary view through a window to protect the camera from splatter and don’t mount the apple on something that could deflect the arrow toward the camera. 

Jello Effect. Because of the very high velocity of the bow motion be aware of the Jello Effect discussed in this thread.   The top and bottom of the bow will be mirror images.  If not, suspect the Jello Effect.  Test for by rotating the camera 90 & 180 degrees and repeating the videos.

Attractive vs. Analytical Videos.  I have no opinion on this issue but I have read that minimizing motion blur might make display videos less attractive.  That is, some motion blur should be present for the most attractive display videos.   When your objective is for more attractive display videos, as opposed to frame-by-frame analysis, experiment with shutter speed to get the most attractive videos.  Slower shutter speeds also allow you to use a lower ISO number and reduce the noise introduced by the higher ISO numbers. If you are doing analytical work always minimize the motion blur.

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82 Reply by Chas Tennis

(8 replies, posted in Bug reports)

coachgeo

Thank you for the analogy, it helped clarify the K video save operation.     

1) I viewed my video from the K folder on K with the track showing. 

2) I saved it again this time being sure to use

“Permanently paint key images data on the video.”

It worked to put the track into the video.  The track is now in this VIMEO video.  http://vimeo.com/25144725
--------------------------------------------------------------
The first occasion I must have used

“Combine video and key images data in the file.”

This method of saving as you describe recorded the information as video plus other (in two files?).  Apparently in this mode K associates the video & track info and will show the track even if it is not in the video.   

I believe that wording for the less apt is always a good idea.   “Key images data” might be synonymous with track data to the knowledgeable.  But I view the term “key images” to mean selected frames of the video with or without overlays.  I don’t recall working with a key image when I did the tracking operation.

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83 Topic by Chas Tennis

(8 replies, posted in Bug reports)

The problem: when I uploaded the file “CIMGO237.AVI with Track”   to Vimeo it plays the video but there is no tracker path displayed. ?

http://vimeo.com/25082854


I downloaded a version of Kinovea 2 weeks ago just before the last freeze. 

I tracked a marker for some distance. 

I saved the video using, I believe-
**   “Permanently paint key images data on the video.”
It is possible that since I can’t distinguish the difference between the two options I may have used –
**  “Combine video and key images data in the file.”
[I'd recommend rewording these.]

I renamed the file “CIMGO237.AVI with Track”.

This file is now in my Kinovea folder.  If I play it in K the tracker path appears. 

Is this tracker path now in the video file "CIMGO237.AVI with Track" or is the path only displayed when viewed in K?

Second, a “CIMGO237-0.00.02.387” jpg file appeared in my Kinovea folder.  I don’t recall creating it but I may have. It is a still of one frame with the complete track path.

[img align=C]http://images2.snapfish.com/232323232%7Ffp5399%3A%3Enu%3D92%3B5%3E359%3E257%3EWSNRCG%3D33%3A7444874348nu0mrj[/img]

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84 Reply by Chas Tennis

(51 replies, posted in Cameras and hardware)

The Casio Ex FH100 is a great camera!

There is one quirk which I don't fully understand. It can easily be worked around.  In full manual mode, "M" on the dial, you set the shutter speed and the "aperture" which is a ND filter.  For the shutter speed I usually use 1/10,000s. At this shutter speed if you leave the ISO setting on AUTO the videos will be too dark.   Simply set also the ISO manually to 800 for a sunny day.  After seeing the video adjust the ISO up or down to get the brightness that you want in the video.  Forget ISO AUTO for high speed videos and fast shutter speeds. 

http://forums.dpreview.com/forums/read. … e=37098733

I don't understand why the FH100 ISO AUTO does this. Speculating, maybe at the faster shutter speeds the camera has trouble computing the proper ISO using AUTO. ? Or it defaults to low ISO.  It is easy to avoid.

I have a very tight fitting case without padding, "Cute case", with a slot to hold a spare battery & SD card.  It will stuff into you pocket but just barely.  http://www.cutecamcase.com/casio_case.html

Rather than print the downloaded or CD copy of the 200 page User's Manual, I bought a paper copy, computer printed, from Casio support, for $10. 

Reply # 552 has a video on camera settings that would have saved me a lot of time.   But disregard what is said about 1/2000s shutter speed and if light allows always set it faster to reduce motion blur.
http://www.golfwrx.com/forums/topic/250 … e__st__540

Let us know how you do.

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85 Reply by Chas Tennis

(51 replies, posted in Cameras and hardware)

The ZR100 may have some improved video features, such as the important capability to focus while recording video, but any improvements are not in the area of high speed video.  In fact the exposure control for the ZR100 is only AUTO, a giant step backward for high speed video.  See the discussion in the first message regarding AUTO exposure control.

Check this point yourself by downloading the User's Manual for the ZR100.

Again, I don't know of another currently available, affordable, high speed video camera with manual shutter control other than the FH100.   If you have one please supply the link that clearly describes the manual exposure control for high speed video. 

What has happened, I believe, is that since the introduction of the breakthrough Casio Ex F1 in 2008 not enough buyers understand the importance of manual control of the shutter speed and consider only frames per second.  They buy a camera and the motion blur is much larger than it would have been with a camera with manual shutter speed control, maybe they are disappointed with high speed video in general.  Unfortunately, the cameras with the superior capabilities for high speed video don't sell as well as they should.   The next design loses capability in high speed video as has happened with the FH100 transition to the new ZR100.

Look at Reply #591 and watch the first video which compares the ZR100 and FH100, the pertinent information starts around 1:50 sec into the video.

http://www.golfwrx.com/forums/topic/250 … e__st__570

UPDATE - 4/9/2014 - Still no manual exposure control.  2012 comments.
http://www.mytpi.com/articles/technolog … ed_cameras

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86 Reply by Chas Tennis

(1 replies, posted in Cameras and hardware)

I don't have much experience with this but here are some first thoughts.

A single video camera works with projected images.   It is exactly similar to how your eye works.  Therefore it is easiest to do some simple demonstrations with the eye to understand what is going on. 

Take a piece of stiff wire, such as cut from a coat hanger, or short piece of solid electrical house wire, pipe cleaner, etc. that will hold its shape.  Take a straight piece and bend an angle, ?, into it. (Simulates a person bending an elbow to ?, etc.) 

1)  hold the piece at arm’s length with one leg horizontal and rotate the angle slowly around.  The apparent angle seen ranges from ? as a maximum to 0°.   

2)  with one leg horizontal and ? at maximum (‘plane’ of the angle perpendicular to the line from your eye) now rotate the apex of the angle toward you.   The apparent angle will go from ? to 180°. 

Any angle ? then can range from 0 to 180° as seen depending on how the angle is oriented.

With one camera you have to be very selective in what you chose to measure & how you measure it. 

Golfer. Side view of a golfer swinging is the easiest as the planes of the swing and the sensor are parallel.

Sprinter. Another special case - again I don’t have experience doing this – would seem to be a sprinter running in a straight line, across the camera’s field of view and about the same distance from the camera on the right as the left (telephoto is best). The leg would be mostly vertical and if the camera were set up with the sensor plane vertical then I believe the angle of the leg would be pretty accurate.  If the legs move toward or away from the camera it would lose accuracy.

For motions with known orientations that are not parallel to the sensor plane I would try to develop a technique using calibration objects with angles to video before, after or during the sports video.  For example, video calibration angles could be made of PVC pipe with 45, 90° or 135°, etc. or better yet pieces of PVC pipe every 20 or 30°.   If a baseball batter swings up at 20° put the calibration angle in that plane and video it.  I don’t know if Kinovea has a tilt capability to match angular calibration for a technique like this.   

For other motions with unknown orientations as may occur in sports I don’t know what to suggest.  Maybe calibration angles could be put in after looking at the video.  For example, the batter was seen to swing up at 35° so video a calibration standard at 35°.

I believe these problems can best be dealt with using multi-camera systems with cameras viewing from different angles and computer processing of the video.

What application are you interested in?

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87 Reply by Chas Tennis

(51 replies, posted in Cameras and hardware)

My interest has been in stop-action frame-by-frame analysis of tennis strokes.  All videos were taken in high speed at 240 fps.   I also view the strokes in slow motion.   
I am not familiar with applications of computer capture using high speed video cameras.  I look forward to seeing some of those applications described in the other threads. 

Casio Ex FH100

To my knowledge--   

No Real-Time Video Out -  The Casio FH100 records to a HCSD card and then afterward that card can be read by a computer.   I'm nearly certain that there is no live video output capability.   

Full User's Manual, starting page 141. No live video output modes are discussed. -

http://support.casio.com/manualfile.php … =001011013

EYE-Fi. The FH100 also has an Eye-Fi capability which I have not used. (pg 156 & 157 of the Casio User's manual)   I believe that Eye-Fi operates by recording to a special Eye-Fi SD card and then the camera seeks a computer that is set up to automatically and wirelessly download from the SD card.  I believe, but am not certain, that the card operates only after the recording is complete.

http://www.eye.fi/how-it-works/basics

Continuous Record. In addition, the camera has a high speed video 'continuous record' mode where it records but only saves, for example, the last two seconds.  Then, if some rapid event is going to occur, but the exact time is unknown, the camera will still catch it.  The camera video button is pressed once to start the recording and a second time after the event to end the recording.  I believe that the only start-stop video control is by the button and that there is no external trigger, but again I'm not certain.

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88 Topic by Chas Tennis

(51 replies, posted in Cameras and hardware)

There is a very large range of frame rates in the camera discussions, for example from 10-1,000 frames per second.  Some of the readers might not be familiar with high speed videography and estimating the most basic camera requirements for their sports.

FRAME RATE (SAMPLING RATE).  30fps is a slow sampling rate that might be adequate for locating players moving around in most sports but it cannot be used for rapid motions such as golf club swings, tennis strokes, baseball hits, throwing, etc because the sampling rate is too slow. 

Consider how far an object (soccer player, tennis racket, arm, etc.) moves between frames for a given frame rate.  We are considering the velocity to be across the frame in all cases. Picture a golfer with the swing viewed from the side.

DISTANCE MOVED = OBJECT VELOCITY / FRAME RATE

For a golf club head traveling 100 MPH or 44.7 m/sec and a camera frame rate of 240 fps:

DISTANCE MOVED = 44.7 m/s / 240fps

DISTANCE MOVED = 186 mm   (each frame time), you catch the club every 19 cm.

For 30fps

DISTANCE MOVED = 1.49 m, inadequate for any useful swing information


MOTION BLUR. Motion blur is determined by the object velocity and exposure time (called "Shutter Speed").  For stop action frame-by-frame examination minimal motion blur can be very important.  (Exactly the same as shutter speed for still photography.)

For a camera viewing an object traveling across the frame - picture the golfer with the swing viewed from the side - the motion blur is equal to:

MOTION BLUR = OBJECT VELOCITY X SHUTTER SPEED

For the same golf club head velocity of 44.7 m/s and a shutter speed of 1/10,000 sec then

MOTION BLUR = 44.7 m/s X 1/10,000 s

MOTION BLUR = 4.47 mm, 1/10,000s is adequate for seeing how the golf club head is oriented.

On the other hand, an exposure time of 1/1,000s results in a motion blur of 44.7 mm - about the size of the entire head of the golf club - too blurry. 

High speed video cameras that operate with AUTO exposure control have unknown exposure times.  The camera's AUTO control will also usually pick an exposure time that is too long resulting in unnecessary motion blur. However, often the available light would have allowed considerably shorter exposure times (faster shutter speeds).

If you want to do stop action frame-by-frame analysis of sports motions be sure to purchase a HSV camera with adequate frame rate and manual shutter speed control.

In June 2011, to my knowledge the Casio Ex FH100 is the only affordable high speed video camera currently available that offers full manual control of the shutter speed.   Speculation is that the FH100 may no longer be manufactured but it is still probably in stock. ……..right now………  I have no financial interest.  Recommend that you download the full user’s manuals when selecting among high speed video cameras.

Each sport motion has different object velocities such as players moving around a field or a golf club head striking a golf ball.  What spatial information (in centimeters, etc.) and what temporal information (in milliseconds, etc.?) are you after?  Best estimate to be refined as you go.... Is the high speed video camera capable of giving you that information with the given object velocities?  Step one is to calculate the DISTANCE TRAVELED BETWEEN FRAMES & MOTION BLUR.

Jello Effect. Another issue for cameras is the Jello Effect caused by recording different parts of the image at very slightly different times.  This effect can cause image distortions and might especially affect higher resolution cameras with many lines of detectors (it takes time to record & readout the additional lines).

Bending golf clubs, Reply #562 -

http://www.golfwrx.com/forums/topic/250 … try3187037

http://www.golfwrx.com/forums/topic/250 … e__st__540

Jello Effect measured for my Casio FH100 Camera -

http://vimeo.com/21529497
https://vimeo.com/29160003

Other sites

dpreview Casio Forum -

http://forums.dpreview.com/forums/forum.asp?forum=1015


Golf site with a long Casio camera thread -

http://www.golfwrx.com/forums/topic/250 … e__st__600

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89 Reply by Chas Tennis

(18 replies, posted in Cameras and hardware)

jbrond wrote:

........One interesting camera currently on the market is the FaceVsion Touchcam N1. It has some interesting features but most important has hardware compression (H.264) internal in the web cam and uses USB. It can do HD in 9 fps but 640x480 in 30fps which is nice for sports. ......................................................It also works with the latest version 0.8.15. The only thing I am missing in Kinovea 0.8.15 is the option to adjust the exposure. Exposure is important if you want to avoid motion blur in the images. Normally you use the "Video source" (DirectShow programming stuff) to do that. But I dont see the properties for enabling that in kinovea? Only selecting the format. Hope to see it soon :-)

Jan

I am not the one to say what can and can't be done with digital technology but here are some basic points to consider relative to motion blur, shutter speed and camera operation.

The motion blur is controlled within the camera by electronics that turn the sensor’s elemental detectors on and off while they are collecting photons.  The on-off time is the shutter speed.  I doubt that any available cameras such as the FaceVsion Touchcam N1 will allow external software to control the camera’s shutter speed electronics. [In some more basic sensors I'm sure it may be possible.]  Please correct.

What is "Video Source"? Does it control cameras?

I see a lot of discussion of cameras with a very wide range of frame rates from 10 fps to 1,000 fps.  I'm getting a little disoriented......sports video applications....10fps, etc. ?  My Casio Ex FH100 camera is high speed video and does not have an output while recording as far as I know (Eye-Fi transfers after recording I believe??). 

For anyone interested only in some very basic high speed video camera issues and requirements for sports I'll open a separate thread.

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90 Reply by Chas Tennis

(20 replies, posted in General)

Color Tracking?

joan wrote:

I was asked by mail about markers and the tracking algorithm.

The automatic tracking in Kinovea works by computing the cross correlation coefficient between a candidate window and the feature window of the previous image.
For each possible position in the search window, we get a score, and the best score is the match (unless it is under a specific threshold in which case we assume the target was lost).

So it is a measure of how much the candidate look like the original.
- Contrasting area will make the matching easier. (marker should have a different brightness than its background. Bright on bright is not so good.)
- It is not invariant to rotation, so if rotating the marker changes its look, it will be harder to match. (triangle, rectangle, square: not so good)
- It will look in the immediate surroundings, so having a target that does not resemble any other part of its vicinity is better to avoid mismatches. (background and other parts on the person should be clear of anything that look like the marker).

To sum it up (based on the theory, I haven't done extensive testing in real conditions yet)
- Circular marker.
- Marker that takes about half the feature window.
- A color and brightness contrast with background that is not present in the rest of the search window.

Please post your findings, experiments, which markers work best, etc.
Anyone to do a video showing how various markers perform ?

To double check, does Kinovea use the color information as well as the brightness for tracking?

Any idea of what might happen with a marker pattern made up of two saturated colors but similar brightnesses, for example, a red circle surrounded by a blue ring?

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