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Matchmoving Problem: PFTrack 5.0 and HD Footage
Dear community,
i have some basic questions about PFtrack and camera setup. since i am not a VFX specialist i hope you can help me out.
i have some HD footage recorded with a Sony HVR-S270E. sony says that it yields a 1/3″ 3CCD sensor. I went to some calculations sites and i found out that there are many different chip sizes in mm for 1/3″ chips. one third of an inch is 8,7mm. Since I know it is a 4:3 chip with anamorphic HD i got this result: 4,8mm height x 3,6 mm width. Does anyone know if those are the correct numbers for the camera chip?
Now, when I capture the video from MiniDV to my hard disk with Premiere Pro CS4 it generates a MPEG video file. Then i convert this file into a sequence of .TIFF images which converts the anamorphic format into 1920×1080 square pixels.
How do I have to setup my PFTrack camera now? It seems that I always get strange results when I put in my 4,8mm height x 3,6 mm width of the chip (focal length is 40mm static). Since the converted image is not 1440*1080 (1.333333) anamorphic anymore… its the same camera but 1920*1080 squarepixels (1.0) do I then have to put in other measures? I’ve heard that setting up correctly the camera configuration before matchmoving is an essential part of the process.
I know its a complicated explanation fo the problem and my english is not very nice 😛 but I hope some of you understand my problem and could help me with it!
Thank you very much in advance,
Hans aka Shixxor
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8 Replies
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hey there,
I matchmove a lot, almost every day with PFtrack. One of the things I find really annoying is to figure the gate size and camera properties of something I was not on set for. It is important to know your camera’s info but not impossible to get excellent results without it.
PFtrack is great at guessing. As longs as you know your focal length (or at least that it’s constant or varying), what kind of camera move it is (nodal pan, free motion) and that you can verify that your framesize is correct (not squished) you should be okay to start tracking. Also before starting check for lens distortion by looking at the straight lines and vanishing points in the shot. If there is distortion you’ll have to remove it before tracking.
If you’re new to PFtrack here are some quick steps that may help you:
1. Setup camera as best as possible
2. Mask out anything that you don’t want to track (anything moving independently like a person or a car).
3. Manipulate your footage by increasing the brightness/contrast in PFtrack (right click on your footage on the left and “Manipulate”).
4. Click on “tracking” at the top and go to tracking parameters. Check off “Preview” and mess with your settings in there to get your desired results. Remember that more trackers does not give you better results, accurate trackers give you better results. Once done, hit the “Auto-track” button and watch it go
5. Once done, Under “tracking” again at the top go to “Clean Tracks…” and lower your “Threshold” and “Rejection Count” to a desired spot. (there are far more advanced ways to do this but for beginners purposes this is a good way to go)
6. Right click on your best auto-tracked features and set them to be “Hard Constraint”. Also, add “User Features” in parts of the screen where auto-tracks may not have done so well. (you can keep manipulating the footage for every User Feature you add. So you can bring out the ground for one track and the building for another).
NOTE: at this point you can actually try to solve the shot and see what kind of results you’re getting.
7. Add “Axis lines”. Draw out your axis lines every 10 frames or so depending on the length of your shot. Remember to set them as X, Y or Z and to know if you’re working in Z-up. (the coordinates Z-up option is in the preferences)
8. now you should be ready to solve. Once solved adjust your ground to math your planar surface in the shot (maybe the ground, maybe a table top).
NOTE: it’s very important that you place test objects in your scene after you’re done to test the accuracy. Place them in both the foreground and background and watch for any little jumps in you’re track.
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There are many more steps you could be taking but I found that these worked well on basic/intermediate shots. Hope this helps someone.
mike.
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Since you work in PFTrack a lot. I was wondering if you have a recommendation for making the image sequences. I still find it, odd to put it mildly, that this is even necessary. But since it is…
I tried a variety of things quicktime pro, photoshop. What I would really like is something a lot more automated and invisible. Like a watch folder or a command line program.
Suggestions? PC or Mac solutions, either, or.
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hey man,
PFTrack can be picky about the kind of footage you feed through it. After Effects (mac or pc) is part of my pipeline and I’m usually working with a DPX sequence which PFTrack processes beautifully. Otherwise you can make a TGA or TIF sequence and those work great too. You should get in the habit of making a sequence for PFTrack for a number of reasons; it CAN modify/corrupt your footage.
If you’re using after effects you can do your masking in there too and then import an image based mask. To do this export a solid black and white video from after effects (also DPX, TGA or TIF) and import as an “Image-based mask” from the file menu in PFTrack. I find this quicker, you might not.
I love this workflow cause you can export your camera right back into after effects and make coolness from there.
Mike.
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Mike,
Thank you so much for laying out those tips. I have a quick question. How do you go about drawing axis lines effectively? I can’t seem to grasp where and how I should be placing them…
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Hey Evan,
The axis lines will do two things for you that I know of.
1. Solve your lens distortion: If you have any curved lines in your shot that you know should be straight then you have lens distortion. You want to apply both ends of the axis lines, but also apply a point in the middle of each of those lines to show PFTrack how the line bends. Once you’ve done this you go to “Lens Distortion” in the “Camera” menu at the top of the screen and hit solve. This will unwrap your image and make those curved lines straight so that you can continue with your solve.
2. Accurately adjust your ground plane: Set axis lines for both axis’ that would be aligned with your ground. For example, if your software is set to “Z-up”, then your ground would be on the XY axis’. These lines should be straight because you’ve undistorted your camera in the steps before. Once you’ve put in your lines, go to “Orient Scene” in the “Camera” menu at the top and voila. Your ground plane should snap to the ground in your shot.
Note: In my past posts I said to apply these lines every 10 frames or so. As it turns out that’s major overkill for most shots. You can do this to a single frame and get results.
Hope this helps.
mike.
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Evan,
After reading your question again I see you were asking “where” to place them.
You place them along there corresponding axis. layout a line, then you can right click on it to choose which axis you want that to be. if your scene has a building in it, you want to place it on the vertical and horizontal lines that you can clearly see. Don’t pick something that looks like a straight line but you’re unsure, like a pole that might be bend or crooked. Again, make sure you have undistorted your camera lens or doing this will just mess up your track.
mike
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Ok cool, I think understand now. I guess it takes a lot practice, because I feel like I tracked everything perfectly, but in the end it’s always way off. I’ll keep working at it.
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Hello there,
Im using PFTrack 4.1 and when i import any dpx sequence is looks corrupted, as in green neon lines. Even if I hit load, the whole seq looks bad.
Ive used tiff/targa seq before & looks fine; and Ive used this same dpx seq in Nuke and its perfect.Any suggestions? I appreciate it!
sara
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