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What is the ultimate Calibration Board Material?

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

Re: What is the ultimate Calibration Board Material?

Postby Bongobat » Mon Dec 02, 2013 8:57 pm

MagWeb wrote:Greg (aka Bongobat) suggested to cover the boards with magnetic paint and to use a print on magnetic foil (e.g. Posterjack.com)

Edit: there are also magnetic foils for standard printers available.


Hi Gunter,

Good to see you again. Yes I have been using magnetic paint and inkjet printable magnetic sheets since the early days, the dawn of laserscanning. I still have some very old calibration patterns that I still tried to test until recently. I use to write on those old patterns the scale number on the front inbetween the dots and would used the eraser tool to erase it and other dark areas before calibration. Seems that eraser tool is gone now so I no longer use any of my older calibration patterns but the V2 work just fine anyway.

I made a new corner similar to my old one recently and took some pictures. I don't know how precise it is but it is simply MDF attached using angle brackets and bolts. The inside is painted with 5 or 6 thin coats of Rust-oleum Specialty Magnetic Primer http://www.amazon.com/Rust-Oleum-247596 ... B003ZW7XL4 After that dried I painted on 2 coats of Kilz flat white latex primer. After about a week I sanded it just a bit smooth to the touch. I think on my older panel I used an oil based primer for the topcoat and then sanded and polished it down to an almost car paint like finish. For what I scanned though that was needless work.

These are similar to the magnetic sheets I use: http://www.staples.com/Avery-Personal-C ... duct_46771

Usually I take the calibration printout off while actually scanning. I guess this would affect the overall scale by some very small percent but makes for the smoothest corner during scanning.

I used this system here to scan the Slave 1, AT-TE and the Darth Vader redux I recently posted. I have personal issues taking up my time lately so I haven't been able to scan or comment as I would like.

Hope this helps some.

EDIT: I originally made a mistake and linked to glossy magnetic printer sheets. The link is now to suitable matte white printable magnetic sheets.

Greg
Attachments
DSCF0571.JPG
MDF Corner before paint
DSCF0628.JPG
Small printout
DSCF0630.JPG
Applying large printout
DSCF0629.JPG
Large printout
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Re: What is the ultimate Calibration Board Material?

Postby MayCrown » Thu Dec 19, 2013 1:21 am

I want to thank all of you guys about your insights..

From what I have experienced, the ultimate calibration board material is GLASS. (Of course I'm not counting the expensive NASA-like solutions (titanium etc.))

Why? It's damn flat. It doesn't loosen up over time, it always stays rigid.

Wood
Pros: The quickest to be found, The quickest to be done. In minutes you have a corner. (To give you confidence most people here use wooden panels including masters like HAL, BONGOBAT. But I think it's a risk. And we're not at their level.)
Cons: Inspect it closely, many wooden panels are not perfectly flat. It can bow to the inside or outside over time.
Cost: Low (I paid 12 $, my carpenter didn't want any money but I paid him nevertheless)

Alupanel
Pros: Very flat. It's better at staying flat.
Cons: You need a machine to make it. Most of the material you find on the market are not perfectly flat but bowed, because the panels are cut from larger panels, and larger panels are bowed during transportations, or while waiting under the sun. (Mine alupanel was from scrap, and because of that it wasn't perfect.)
Cost: Higher (I paid 15 $, but I had brought my own material which was a scrap panel I had gotten for free, I paid only for labor)
If you're considering to use alupanel, buy one from the DAVID store, it's your best choice.

Glass
Pros: It owns. It's the flattest thing you will find.
Cons: Heavy. And large panels will be heavier.
Cost: Lowest (I paid 7 $ ---- all inclusive)

Acryclic
I got a quote for acryclic panel, because of the weight of my glass panel. But the man said it wouldn't be perfectly flat. So I didn't order an acrylic panel. But if consider, it has the higest cost. (35 $)
Attachments
1.jpg
wooden (RISKY)
2.jpg
alupanel (NEEDS EFFORT)
3.jpg
Glass (My favourite, you will like it, it's like an airbag)
http://www.shapeways.com/shops/MayCrown
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Re: What is the ultimate Calibration Board Material?

Postby MayCrown » Thu Dec 19, 2013 1:26 am

I want to also show you how wooden material is not reliable at all. Look from this point of view.

You can see in the picture that from the point I've shown with the arrow on the panel is bowed to the inside.
Attachments
4.jpg
http://www.shapeways.com/shops/MayCrown
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Re: What is the ultimate Calibration Board Material?

Postby WalterMo » Thu Dec 19, 2013 9:49 am

Bigger corners (>1 square meter) could be built of hollow door leafs. See this site (in German) where the first 3 images show different designs. The appropriate weight (kg / square meter) is mentioned in the description to each image:
http://www.google.de/imgres?imgurl=http ... CQ&dur=485

These kind of doors are nearly perfectly flat. Have just held an aluminium square tube at our > 20 years old indoors.
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Re: What is the ultimate Calibration Board Material?

Postby argo » Thu Dec 19, 2013 1:42 pm

MayCrown wrote:Glass (My favourite, you will like it, it's like an airbag)

Hi Luna... oops MayCrown (It is so difficult to forget that previous username. but i promise i will do my best :wink: )
How do you stick the paper to the glass? using a simple tape?
and how thick is your glasses?

Regards,
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Re: What is the ultimate Calibration Board Material?

Postby MayCrown » Thu Dec 19, 2013 3:08 pm

6mm is optimum

The paper is a mat self-adhesive paper I've bought from a nearby stationery.
http://www.shapeways.com/shops/MayCrown
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Re: What is the ultimate Calibration Board Material?

Postby MagWeb » Thu Dec 19, 2013 6:21 pm

Just a suggestion to MayCrown's corner made of glass:

I'd cover the baseplane made of glass with some black or at least not such reflective stuff. The current glass surface may reflect stray light back to the calibration planes.
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Re: What is the ultimate Calibration Board Material?

Postby hunkatibor2 » Thu Dec 19, 2013 6:27 pm

Hi
http://forum.david-3d.com/viewtopic.php?f=7&t=5786
Image
Yes the glass is very good for me.
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Re: What is the ultimate Calibration Board Material?

Postby Normand Blais » Thu Jan 02, 2014 7:51 pm

Hi every one
I use drywall,( gyprock )5/8 it is pretty flat . I just cut the back ,the front paper is use as a hinge. I glu the dot paper that I print .
But glass is going to be my next try
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