Author Topic: A handy, cheap white balance tip if you don't have a reference card  (Read 8825 times)

Andy600

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There are not many substitutes for having a proper white balance reference when shooting (white balance card, Colorchecker etc)  but here is one that will help you get accurate white balance and it's very cheap.

Polytetrafluoroethylene or PTFE - Teflon.

PTFE and is usually found in a plumbers toolkit. It is a white, stretchy, non-stick tape used for sealing pipes but it does have another very useful property. PTFE is an almost perfect (~99%) Lambertian reflector i.e. it's ideal for providing an accurate white balance reference.

You can pick up a roll of PTFE tape at most hardware stores for a couple of dollars/euros and make your own white balance reference card by wrapping the tape around some cardboard. You need to wrap several layers as the tape is a little opaque but a small roll should give you a portable 6"x4" card that you can keep in your camera bag. It's not as robust as a commercial reference card but it's cheap and is far more accurate than a lot of the cheaper white balance cards that you can find on eBay.

Lambertian Reflectance https://en.wikipedia.org/wiki/Lambertian_reflectance
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DeafEyeJedi

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A handy, cheap white balance tip if you don't have a reference card
« Reply #1 on: September 24, 2015, 08:08:46 PM »
Nice tips, will look into more on this and thanks for sharing!
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ziggy53

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #2 on: October 06, 2015, 02:22:39 AM »
An excellent tip! I do suggest that the "~99%" figure is achieved using at least 3 - layers of tape, as mentioned in this article:

"Optical Reflectance Measurements for Commonly Used Reflectors"
http://www.osti.gov/scitech/servlets/purl/957053

ansius

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #3 on: October 06, 2015, 08:21:53 AM »
some notes tough

  • white balance card must be matte, glossiness will screw up your measurement.
  • you should also have gray card for proper exposure, and that has to be calibrated, at least roughly
  • some of tend tapes tend to be bluish, you should check them in sunlight & tungsten and should give the same result
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Andy600

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #4 on: October 06, 2015, 03:01:43 PM »
@ziggy53 - Totally agree. PTFE is cheap enough and a small roll will usually have enough coverage for more than 3+ layers covering a practical sized surface area.

more links to other scientific studies of PTFE, Tyvek etc:

http://escholarship.org/uc/item/82r9k9rn#page-3

http://www.researchgate.net/publication/254060766_Reflectivity_Spectra_for_Commonly_Used_Reflectors


@ansius

I agree with all your points, especially when it comes to gloss vs matt finish. I have a couple of DSC CamAlign charts and if I'm honest they are a b**ch to use and you must light very carefully. DSC CamWhite is a very good white reference (probably the best) but being glossy, falloff and reflections make it very difficult to use out of a studio environment.

There are plenty of cheap gray cards on eBay but I would recommend Kodak Gray Cards or better still, the Plus version http://motion.kodak.com/motion/Products/Lab_And_Post_Production/Gray_Card/index.htm.

Something like this: http://www.ebay.com/itm/New-JJC-GC-2-3in1-3-Color-Digital-Card-Set-for-White-Balance-Adjustment-/321300872260 provides a usable but small 18% neutral reference for a few dollars but the white card is not neutral and the black card is useless i.e. throw them in the bin.

Reference black level on most cards (unless talking in terms of print density) are always useless and you'll get much better results with a DIY blacktrap (a small, sealed box with a small hole cut in it, lined with a non-reflective black material and shot angled away from the lightsource). It's only useful a luminance reference (not color) unless you go extreme and line it with http://www.acktar.com/category/products/lights-absorbing-foils but it's pricey.



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DeafEyeJedi

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #5 on: October 06, 2015, 04:49:59 PM »
Great info, @Andy600 and definitely leads me to a question -- Does Kodak Gray Card Plus give close similarities results as Xrite's ColorChecker Passport especially on the color parts? 
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budafilms

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #6 on: October 07, 2015, 09:00:38 AM »
Good post.

It's important to know that Teflon, in some countries like mine - Argentine -, are prohibited. Specially for plumbers that work or touch a lot with the hand. This advice is not for intimidate someone, just for check in your country if the regulations permit to handle this kind of products.



pilgrim

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #7 on: October 07, 2015, 09:24:03 AM »
Thanks.
It's very useful, when often move around in different countries.

How about the white colour of the foam which we use to protect electronic equipment inside the cartoon box for transport/delivery.
I am sure we have a lots of that, from the camera box, computer, etc. Now the new box often only with cartoon, without that foam.
Did anyone try this foam as white balance tool or compare to the Kodak Card ?

Once again, thanks.

ansius

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #8 on: October 07, 2015, 11:02:35 AM »
foams color would shift owner time in contact with sun (actually any UV source) as it deteriorates it. There are not that many plastics that are white and UV resistant.

my simple solution has been good white a4 sheet of paper. ok it's more like %5 gray but you can get it anywhere ;)
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Andy600

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #9 on: October 07, 2015, 12:37:09 PM »
@DeafEyeJedi - Both the Colorchecker PP and the Kodak Gray Card+ use Munsel color patches and they are provided with target values. The Kodak has RGB and the PP has RGB, XYZ and Lab. If you know what the measured target values are for the chart you can calibrate a real-world shot of the chart to match the target values.

The ColorChecker PP would probably be more useful to you because there are many calibration tools that already work with the MacBeth 24 patch chart and non that work with the Kodak+ out of the box that I know of. Alternatively you could make your own reference chart but you'll need a spectrophotometer and a good D50 lightsource. The Colorchecker PP is very good but it's also very small and not ideal as an exposure reference so you should pair it with a good size graycard.

@budafilms - I didn't know that. I read that Teflon could emit nasty chemicals under heat but DuPont had done something about it. If there is any possibility of harm from PTFE tape then of course it should be avoided.

@pilgrim - I'm not sure about packing foam. You would need to measure it. Ansius is right in saying that UV can affect the material so even if it's neutral enough to use now it may not be after a few weeks of use.

@ansius - I'm sure there are some neutral A4 papers but knowing which ones is difficult unless you can measure them. A white balance reference needs to remain neutral across the visible spectrum and if it doesn't it will cause a colorcast. I wouldn't trust paper unless I'm sure of it's neutrality.

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pilgrim

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #11 on: October 14, 2015, 01:36:02 AM »
@ansius and @andy :
Thanks for your reply. I drop the idea. For a moment I don't have the Kodak one.

I try another idea : doing custom white balance with the lens cover by the white cup/bowl, a kind of plastic, but not exactly plastic.
I corrected by dv resolve, it's look good.
It's not perfect but it's useful, at least better than the menu in camera (Auto, cloud, shade, etc).

Thank for many good idea and explanations.

pilgrim

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #12 on: October 17, 2015, 08:32:49 PM »
One more question...
I buy the DVD blank normally with the spindle package (50 pieces) white color for ink jet, and later print the design for the cover on the DVD.
It's cost less than 1 euro each disk.
Did anyone know if this white color is enough good for white balance reference ?

Thanks...

Sergey Pylypenko

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #13 on: November 03, 2015, 02:50:23 PM »
Nice finding about the tape!
I tried many WB cards with no success and then accidentally found a great solution that is working 90% for me.  For those who use iPhone (they might have the app for other platforms) go to iTune store and find 'Manual Cam' app.  I'm not sure if paid something, but it's very chip.  Go to settings and set 'ui mode' to 'pro'.  When turn on Manual Cam again you will see WB in Kelvin among other settings. Point to the scene you want to shoot with your Canon and make a screen shot.  Now you have a pretty accurate WB for your post.  In rare occasions it screws up — just restart the app.  Greatest benefit is that one can see at a spot if the WB is correct by comparing what's on iPhone and what's real.

DeafEyeJedi

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Re: A handy, cheap white balance tip if you don't have a reference card
« Reply #14 on: November 03, 2015, 04:45:30 PM »
Which iOS app are you referring to exactly?
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