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Help! Camera Calibration Fails - SL DSLR

The place for questions, problems, comments and tips regarding the camera calibration.

Help! Camera Calibration Fails - SL DSLR

Postby hodgenhoff » Fri Aug 23, 2013 3:46 pm

Hi,

I'm very excited to use the functionality of this platform and have been slowly constructing my SL setup. The last piece of the puzzle, the projector, was finally purchased. No matter what I attempt, I have not been able to successfully calibrate the camera though :(

Setup:
David-Laser Scanner 3.8.1 (64 and 32)
Hardware setup: Image Sequence
Canon t2i (18-55mm lens, Using fully zoomed-in, lowest resolution ~6mp)
Brookstone HDMI Pocket Projector (DLP)
Calibration points - V3_A4
3d Printed 90* alignment squares
Protractor for 30* relative offset of Projector and Camera

Attached are some pictures of my setup in the spare bedroom. I don't have the laptop attached at this time but you can see the general setup.
David_setup_01_001.jpg

David_setup_01_002.jpg



I took a screen shot to show the most recent results. I have rebuilt the Calibration Corner 3 times, each time taking more care to ensure a perfect 90*. This last time I created the black 90* squares and thought my worries were over. Only it looks like the alignment is more off now than before :( I have been able to have the green "X"s align better, of the hundred or so attempts, 95% of the time I get an error 80% of the way through the calibration that says there is not a valid mapping between points.


I have searched the forum extensively and have found a lot of great info and I'm hoping there will be some assistance here with my situation!

Please help! I've been waiting years to use this awesome tech!
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Re: Help! Camera Calibration Fails - SL DSLR

Postby hodgenhoff » Mon Aug 26, 2013 3:30 pm

Update:

After running through a few different scenarios, I decided to uninstall the software package and run a fresh build. Unfortunately it failed to calibrate after re-install. It does show the calibration "x"s more aligned as I would expect to see. (See attached).
Screenshot_02_reinstall.jpg


On a side note, and this was just an observation, I noticed that the system runs through all the calibration patterns during this step of the camera calibration. It was my understanding that the camera calibration only used the gray "pattern" screen, correct? If it needs all the patterns for calibration of the camera, that is probably my issue there ha!

Can someone confirm that the calibration for the camera only requires the gray screen or all horizontal/vertical patterns?

Thanks.
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Re: Help! Camera Calibration Fails - SL DSLR

Postby manish » Mon Aug 26, 2013 3:50 pm

hi,

1. try to sharp focus the six rings only by moving camera little closer.
2. cam and proj. position r ok, but increase the height of cam more then projector height
no need to see all rings.
this would do the successful calibration.

Regards

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Postby hal » Tue Aug 27, 2013 5:33 pm

Hello hodgenhoff,

How you load the photo from your camera? are you using the image grabber? or the live-view streaming?
In the past I had similar problem when used the zoom on my Canon. Please, try a calibration moving to a closer position the camera to the panes and less zoom.

Mattia
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Re: Help! Camera Calibration Fails - SL DSLR

Postby hodgenhoff » Tue Aug 27, 2013 7:07 pm

Manish, thank you for your suggestions. Unfortunately, I still am unable to calibrate.

+ raised the camera level so that it sits above the projector's elevation by about 130mm.
+ Placed camera closer to calibration corner to zoom-in on 6 rings
+ Centered camera directly at Corner center
+ Replaced 55mm lens with 75-300mm telephoto to achieve less distortion
+ Dropped f-stop to lowest setting 4.5
+ ISO 100
+ Shutter Speed is 1/20

Hal, thank you also for your input. I have been using the Image Grabber. I just ran some tests with the camera 18-55mm lens zoomed to 0%. Unfortunately it was not successful.
2013-08-27_13-51-34_837.jpg


At this point I suppose it is possible that my craftsmanship on the calibration corner is still not 100% perfect. As far as tech troubleshooting, it looks like we are right on target. That really just leaves the Corner, which I cannot believe it would need to be more precise. I suppose it is possible at this point though.

DSLR users:
Do you resize/resample your images before importing to a smaller scale?
Anyone using a telephoto/zoom lens?

Thanks!
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Postby hal » Wed Aug 28, 2013 12:58 am

mmmmm
so strange. Please try to make a calibration with a wider point of view.
Try to have a view from down or from up of the markers, so the prospective effect will be increased. Just a test.
Don't think the problem is the calibration panel. Seems ok.

Mattia
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Re: Help! Camera Calibration Fails - SL DSLR

Postby hodgenhoff » Wed Aug 28, 2013 6:31 am

hal wrote:mmmmm
so strange. Please try to make a calibration with a wider point of view.
Try to have a view from down or from up of the markers, so the prospective effect will be increased. Just a test.
Don't think the problem is the calibration panel. Seems ok.

Mattia


Mattia, I got home a few minutes ago and decided to give the new angle a shot or two before calling it a night.
2013-08-28_01-10-46_291.jpg


Unfortunately, the test didn't yield success. At this point I'm beginning to firmly believe it's the Corner. I plan to use "mod podge" this next time around to seal the printouts flat, my last "glue stick" job appears to have some minor wobble on the surface.

4th time's a charm, right? ;)

Thanks again for the input.
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Postby hal » Wed Aug 28, 2013 2:34 pm

2x mmmmmmm

... try negative corner.

I'm starting to be lost...
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Re: Help! Camera Calibration Fails - SL DSLR

Postby hodgenhoff » Thu Aug 29, 2013 6:15 am

I spent some time this evening reading through some threads about the "Negative Corner". And I came across a thread that has me thinking.

The Return of the Negative Corner thread:
viewtopic.php?f=15&t=2752&p=19466&hilit=the+return+of+the+negative+corner#p19466

MagWeb has provided a lot of inspiration as I kept running across lot of his work. One thing he has done on occasion is upload cam images for others to try. In similar fashion I have uploaded an image and would like to see if anyone can calibrate it on their computer. I read somewhere that image grabber wasn't used that often anymore and or potentially broken beyond v3.5: (viewtopic.php?f=15&t=5708&hilit=image+grabber)...

Is v3.5 available for download, and if so, where can I find it?
If you have v3.5, can you attempt to calibrate a camera to this provided image? Scale (142.2mm)
I ran a rebuild of my .NET 4.5 install with no luck (I saw this was an issue with 3.7).
I also downloaded a group of images provided by MagWeb which can calibrate on his computer yet, are unable to calibrate on mine :(

I am starting to question if David 3.8.1 could be the issue. Anyone have 3.5 installer so I can verify?

Thanks
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Re: Help! Camera Calibration Fails - SL DSLR

Postby Bobby » Sat Aug 31, 2013 2:11 am

Check your camera to projector lens to lens centerline distance & calibration pattern to camera/projector lens as per the David manual: http://wiki.david-3d.com/david3_user_ma ... ured_light

Don't give up - distances are very important. Be patient, you will be rewarded!
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Re: Help! Camera Calibration Fails - SL DSLR

Postby hodgenhoff » Sun Sep 01, 2013 1:55 am

+5 points to WalterMo. After installing 3.5.1, first calibration attempt:

Screenshot_05.jpg



More updates to follow! :)
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Re: Help! Camera Calibration Fails - SL DSLR

Postby Sven » Thu Sep 05, 2013 10:31 am

Hi Hodgenhoff,

Sorry I'm late here. I hope I have understood the problem correctly.

The CAMERA calibration requires only one image (no pattern, just black and white calibration markers).
The PROJECTOR calibration requires a full set of projected patterns.

Since version 3.6: In Hardware Setup, when you set DAVID to "Structured Light Setup", a click on "Calibrate" will calibrate camera AND projector directly after each other. That' s what happens in your screen shot from August 26. The green crosses indicate that the CAMERA calibration was successful, then DAVID has tried the PROJECTOR calibration, which failed (see error message text). Probably failed because you did not supply the pattern images, or not in the right order etc.

In DAVID 3.5 (or if you had set any version to Laser Scanner Setup) the calibration is separate. A click on "Calibrate" calibrates only the camera. That has worked (your post from September 1), but you would still have to calibrate the PROJECTOR (in Structured Light menu).
I recommend you don't use the old version. Maybe even use the latest beta: http://forum.david-3d.com/viewtopic.php?f=16&t=5778

I suggest you start with a live camera, not Image Grabber, to get some first results.

In the Image Grabber, you should always import a whole series of images. The file names are important. I have tried to explain it here: http://forum.david-3d.com/viewtopic.php?f=15&t=5708&p=27320#p27290
I hope this helps.

Sven
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Re: Help! Camera Calibration Fails - SL DSLR

Postby Lunat1c » Mon Sep 23, 2013 6:26 pm

Your calibration panel is not precise nor smooth.. It is lousy. Why do you risk it? I was doing what you did in the beginning and got no where. My calibration board was lousy too. Don't waste such a good hardware and your time for that.
Mitsubishi xd 206u, logitech pro9000, acer 3820tg
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Re: Help! Camera Calibration Fails - SL DSLR

Postby Lunat1c » Mon Sep 23, 2013 7:33 pm

I know why you risk it.. Because you're so excited and want to quickly get down to it. But as far as I've seen and contrary to our feelings, the process of scanning needs patience.
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