Stop motion swing analysis at DVinfo.net

Go Back   DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XH Series HDV Camcorders

Canon XH Series HDV Camcorders
Canon XH G1S / G1 (with SDI), Canon XH A1S / A1 (without SDI).


Reply
 
Thread Tools Search this Thread
Old March 22nd, 2007, 09:51 AM   #1
Wrangler
 
Join Date: Sep 2001
Location: Northern VA
Posts: 4,298
Stop motion swing analysis

Mark Rosen posted a comemnt on using 30p vs 60i to do stop motion analysis of a bat swing. Because the thread is closed, and a quick search did not turn up anything obvious on video for swing analysis:

I would think that 60i (with high shutter speed to reduce motion blur) will provide a more useful result because you will have twice as many samples (one every 1/60 rather than one evey 1/30) to look at. This is especially valuable for fast motion events such as a bat or golf swing. And you may find that even a field every 1/60 may not be enough sample per swing.

As I understand it, at contact with the ball a bat is moving pretty fast, maybe around 90 feet/second depending on the player level. At 30 samples per second (30P) you would likely miss a lot of the swing, and 60i, while lower vertical resolution due to interlace, may prove more useful overall as you work with 2x am many individual fields rather than full frames.
__________________
dpalomaki@dspalomaki.com
Don Palomaki is offline   Reply With Quote
Old March 22nd, 2007, 12:43 PM   #2
Major Player
 
Join Date: Dec 2003
Location: Seattle WA
Posts: 209
I agree. If it were for analysis, 60i, deinterlaced to 720P 60 would give you more temporal resolution.
__________________
Stefan Scherperel
SSE Productions
http://www.stefweb.net
Stefan Scherperel is offline   Reply With Quote
Old March 22nd, 2007, 07:55 PM   #3
Regular Crew
 
Join Date: Feb 2005
Location: Illinois
Posts: 26
Don,

Thanks for keeping my post alive. I tried a search on the subject but did not really find anything. I do not understand why my post was closed, whatever.

Anyway I wanted to mention that I believe Canon's own broshures talks about how their 30F mode is ideally suited for sports as every frame is captured clearly and independently. I do not think shooting in interlace 60i mode really adds additional frames but rather divides each frame in two. This allows analog TV to draw the picture with the gun making two passes for each frame.

I may be misunderstanding this. I learned that the XH A1 chip set is interlaced and therefore the camera still captures in interlace, but then does an internal interpolation and then spits out 30F. I was just interested as to the quality of this proccess verses true Progressive capture as in the XL2.

Thanks,


Mark
Mark Rosen is offline   Reply With Quote
Old March 22nd, 2007, 09:08 PM   #4
New Boot
 
Join Date: Feb 2007
Location: Kingston
Posts: 23
holy confused

I profess to be confused by that last post. Here's how I understand it...

A chip that's 60i means it will capture 60 fields per second. That's the key.

HDV 60i will be laid down on the tape as 2 fields per frame. Thus 60 fields per second. No muss, no fuss.

30F will require that the interlaced fields be mathmatically combined to form a single frame. Some sort of a frame blending algorithm (called deinterlacing) is applied to the two interlaced fields and voila, a single frame is magically created and put onto the tape. The generated frame is never going to 'stop' the action as effectively as the raw data in the fields, it just may look more clear.
Dave Mody is offline   Reply With Quote
Old March 23rd, 2007, 05:10 AM   #5
Major Player
 
Join Date: Mar 2006
Location: Helsinki, Finland
Posts: 393
Quote:
Originally Posted by Mark Rosen View Post
I do not think shooting in interlace 60i mode really adds additional frames but rather divides each frame in two. This allows analog TV to draw the picture with the gun making two passes for each frame.

I may be misunderstanding this. k
Well you are. 60i is 60 fields per second. That is 1440x540 at 60 fps.

30p is 1440x1080 frames per second.
Mikko Lopponen is offline   Reply With Quote
Old March 23rd, 2007, 05:11 AM   #6
Major Player
 
Join Date: Mar 2006
Location: Helsinki, Finland
Posts: 393
Quote:
Originally Posted by Dave Mody View Post
Some sort of a frame blending algorithm (called deinterlacing) is applied to the two interlaced fields and voila, a single frame is magically created and put onto the tape. The generated frame is never going to 'stop' the action as effectively as the raw data in the fields, it just may look more clear.
It's not magic and it's just as "stopped" as the interlaced frame. If you want clear then just up the shutter speed.
Mikko Lopponen is offline   Reply With Quote
Old March 23rd, 2007, 05:43 AM   #7
Wrangler
 
Join Date: Sep 2001
Location: Northern VA
Posts: 4,298
Mark.
Try both methods (60i and 30p) and see which gives the result closest to what you seek

For relatively slow action ( a peson sprinting at 10 mph (for example, such as instant replay of a tag, 30 fps is probably adequate for most purposes.)

Don
__________________
dpalomaki@dspalomaki.com
Don Palomaki is offline   Reply With Quote
Old March 23rd, 2007, 01:02 PM   #8
Major Player
 
Join Date: Dec 2003
Location: Seattle WA
Posts: 209
I think people are way overanalyzing this whole thing.

60i = image sampled 60x per second

30P = image sampled 30x per second

etc.

now granted 60i when deinterlaced to 60p will be lower resolution than 30p, 1080 60i deinterlaced to 720 60P looks phenominal. Just remember that if your intent is to slow this footage down and analyze frame by frame 720 60p will give you twice as many frames as 1080 30p. Also remember to shoot with a minimum os 1/120th sec shutter speed, you could go higher on this if you want no motion blur on the club as you are swinging.
__________________
Stefan Scherperel
SSE Productions
http://www.stefweb.net
Stefan Scherperel is offline   Reply With Quote
Old March 23rd, 2007, 02:01 PM   #9
Regular Crew
 
Join Date: Oct 2006
Location: Brooklyn
Posts: 161
The most important trick here for great looking slow-mo out of 60i or 50i is fields->frames conversion. Barlow Elton has posted some nice example in this thread:

http://www.dvinfo.net/conf/showthread.php?t=75384

Video clip may not be available, but description of the method is there.
Bogdan Tyburczy is offline   Reply With Quote
Old March 25th, 2007, 11:24 PM   #10
Regular Crew
 
Join Date: Feb 2005
Location: Illinois
Posts: 26
best options for slomo

Thanks Don and everyone who posted with their help.

I have been doing a bit of research over the past couple of days regarding slomo techniques. I currently have PP 1.5, CS2 and Encore 2.0 etc.

I do not have After Effects. Here are my questions:

The sample slomo clip of people with shopping carts that Barlow Elton posted. Was that completely done within A/E and no third party plug in such as Twixtor? If so, pretty darn impressive.

I am ready to make the purchase of A/E 7.0. I noticed that there is a pro version for $999.00 and a standard for $699.00.
Does the standard version have all the needed tools, (i.e frame doubling or intopolation needed to convert 60 fields to 60 frames P) to do the quality slomo of Barlow Elton's clip? Or do I need the Pro version of A/E?

With A/E is threre any reason that would prevent me from being able to import my slomo back into PP and then output to DVD?

Lastly, I see there is a plug in for Twixtor for Premiere Pro. Would I be better off getting this plug in in terms of slomo quality?

I realize that I did not provide the link for the clip, I will try to find it now.


Thank,

Mark

Last edited by Mark Rosen; March 25th, 2007 at 11:35 PM. Reason: another question
Mark Rosen is offline   Reply With Quote
Old March 25th, 2007, 11:45 PM   #11
Wrangler
 
Join Date: Oct 2003
Location: DFW area, TX
Posts: 6,108
Images: 1
Just to add to this thread a bit. I agree that 60i or 60P for that matter, is going to be marginal for registering the swing of a bat or golf club clearly at impact. I am experimenting with 60P overcrank on my F350 for the purpose of recording and analyzing golf swings. For best results, get as much light as you can and use a high shutter speed (1/500 or faster) and stop down for deeper DOF if shooting from in front of or behind the person doing the swinging.

Oddly enough, my little Panasonic 953 has a feature for swing analysis that grabs a number of frames but increases the sampling rate to a higher number towards the end of the interval to more precisely capture impact.

Here's some golf info for you to crunch on. Most tour players have a club head speed at impact of 120mph to 130mph. That should allow you to calculate how fast you want the shutter speed in order to freeze that motion.

While you can freeze the individual frames, it's getting enough frames within a second that's the hard part.

-gb-
Greg Boston is offline   Reply
Reply

DV Info Net refers all where-to-buy and where-to-rent questions exclusively to these trusted full line dealers and rental houses...

Professional Video
(800) 833-4801
Portland, OR

B&H Photo Video
(866) 521-7381
New York, NY

Z.G.C.
(973) 335-4460
Mountain Lakes, NJ

Abel Cine Tech
(888) 700-4416
N.Y. NY & L.A. CA

Precision Camera
(800) 677-1023
Austin, TX

DV Info Net also encourages you to support local businesses and buy from an authorized dealer in your neighborhood.
  You are here: DV Info Net > Canon EOS / MXF / AVCHD / HDV / DV Camera Systems > Canon HDV and DV Camera Systems > Canon XH Series HDV Camcorders

Thread Tools Search this Thread
Search this Thread:

Advanced Search

 



Google
 

All times are GMT -6. The time now is 10:20 AM.


DV Info Net -- Real Names, Real People, Real Info!
1998-2017 The Digital Video Information Network